<?xml version="1.0" encoding="UTF-8"?>
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<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:ns4="http://www.w3.org/1999/xhtml" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" xmlns:scilab="http://www.scilab.org" xml:id="bvode" xml:lang="en">
    <refnamediv>
        <refname>bvode</refname>
        <refpurpose>boundary value problems for ODE using collocation
            method
        </refpurpose>
    </refnamediv>
    <refnamediv xml:id="bvodeS">
        <refname>bvodeS</refname>
        <refpurpose>Simplified call to bvode</refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>Syntax</title>
        <synopsis>
            zu = bvode(xpoints,N,m,x_low,x_up,zeta,ipar,ltol,tol,fixpnt,fsub,dfsub,gsub,dgsub,guess)
        </synopsis>
      <para></para>
        <synopsis>
            zu = bvodeS(xpoints,m,N,x_low,x_up,fsub,gsub,zeta, &lt;optional_args&gt;)
        </synopsis>
    </refsynopsisdiv>
    <refsection>
        <title>Arguments</title>
        <variablelist>
            <varlistentry>
                <term>zu</term>
                <listitem>
                    <para>
                        a column vector of size <literal>M</literal>. The solution of the ode evaluated
                        on the mesh given by points. It contains  <literal>z(u(x))</literal> for each requested
                        points.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>xpoints</term>
                <listitem>
                    <para>an array which gives the points for which we want to observe
                        the solution.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>N</term>
                <listitem>
                    <para>a scalar with integer value, number of differential equations
                        (<literal>N</literal> &lt;= 20).
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>m</term>
                <listitem>
                    <para>
                        a vector of size <literal>N</literal> with integer elements.
                        It is the vector of order of each differential equation:
                        <literal>m(i)</literal> gives the order of the <literal>i</literal>-th differential
                        equation. In the following, <literal>M</literal> will represent the sum of the
                        elements of <literal>m</literal>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>x_low</term>
                <listitem>
                    <para>a scalar: left end of interval</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>x_up</term>
                <listitem>
                    <para>a scalar: right end of interval</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>zeta</term>
                <listitem>
                    <para>
                        a vector of size <literal>M</literal>, <literal>zeta(j)</literal> gives <literal>j</literal>-th side
                        condition point (boundary point). One must have <literal>x_low&lt;=zeta(j)
                            &lt;=zeta(j+1)&lt;=x_up
                        </literal>
                    </para>
                    <para>All side condition points must be mesh points in all meshes
                        used, see description of <literal>ipar(11)</literal> and
                        <literal>fixpnt</literal> below.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>ipar</term>
                <listitem>
                    <para>an array with 11 integer elements:</para>
                    <para>
                        <literal>[nonlin, collpnt, subint, ntol, ndimf, ndimi, iprint,
                            iread, iguess, rstart,nfxpnt]
                        </literal>
                    </para>
                    <variablelist>
                        <varlistentry>
                            <term>nonlin: ipar(1)</term>
                            <listitem>
                                <para>0 if the problem is linear, 1 if the problem is
                                    nonlinear
                                </para>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>collpnt: ipar(2)</term>
                            <listitem>
                                <para>Gives the number of collocation points per subinterval
                                    where <literal>max(m(j)) &lt;= collpnt &lt;= 7</literal>.
                                </para>
                                <para>
                                    If <literal>ipar(2)=0</literal> then <literal>collpnt</literal> is set to  <literal>max( max(m(j))+1, 5-max(m(j)) )</literal>.
                                </para>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>subint: ipar(3)</term>
                            <listitem>
                                <para>Gives the number of subintervals in the initial mesh. If
                                    <literal>ipar(3) = 0</literal> then <literal>bvode</literal> arbitrarily sets
                                    <literal>subint = 5</literal>.
                                </para>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>ntol: ipar(4)</term>
                            <listitem>
                                <para>Gives the number of solution and derivative tolerances.
                                    We require <literal>0 &lt; ntol &lt;= M</literal>. <literal>ipar(4)</literal>
                                    must be set to the dimension of the <literal>tol</literal>
                                    argument or to <literal>0</literal>. In the latter case the
                                    actual value will automatically be set to
                                    <literal>size(tol,'*')</literal>.
                                </para>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>ndimf: ipar(5)</term>
                            <listitem>
                                <para>
                                    Gives the dimension of <literal>fspace</literal> (a real
                                    work array). Its value provides a constraint on <literal>nmax</literal> the
                                    maximum number of subintervals.
                                </para>
                                <para>
                                    The <literal>ipar(5)</literal> value must respect the constraint
                                    <literal>ipar(5)&gt;=nmax*nsizef</literal> where
                                    <literal>nsizef=4 + 3*M + (5+collpnt*N)*(collpnt*N+M) + (2*M-nrec)*2*M</literal>
                                    (<literal>nrec</literal> is the number of right end boundary conditions).
                                </para>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>ndimi: ipar(6)</term>
                            <listitem>
                                <para>
                                    Gives the dimension of <literal>ispace</literal> (an integer work array).
                                    Its value provides a constraint on <literal>nmax</literal>, the maximum number of
                                    subintervals.
                                </para>
                                <para>
                                    The <literal>ipar(6)</literal> value must respect the constraint
                                    <literal>ipar(6)&gt;=nmax*nsizei</literal> where
                                    <literal>nsizei= 3 + collpnt*N + M</literal>.
                                </para>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>iprint: ipar(7)</term>
                            <listitem>
                                <para>output control, may take the following values:</para>
                                <variablelist>
                                    <varlistentry>
                                        <term>-1</term>
                                        <listitem>
                                            <para>for full diagnostic printout</para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>0</term>
                                        <listitem>
                                            <para>for selected printout</para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>1</term>
                                        <listitem>
                                            <para>for no printout</para>
                                        </listitem>
                                    </varlistentry>
                                </variablelist>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>iread: ipar(8)</term>
                            <listitem>
                                <variablelist>
                                    <varlistentry>
                                        <term>= 0</term>
                                        <listitem>
                                            <para>
                                                causes <literal>bvode</literal> to generate a uniform initial
                                                mesh.
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= xx</term>
                                        <listitem>
                                            <para>Other values are not implemented yet in
                                                Scilab
                                            </para>
                                            <variablelist>
                                                <varlistentry>
                                                    <term>= 1</term>
                                                    <listitem>
                                                        <para>
                                                            if the initial mesh is provided by the user it is defined in <literal>fspace</literal> as follows: the mesh
                                                            will occupy <literal>fspace(1), ..., fspace(n+1)</literal>. The user needs to supply only
                                                            the interior mesh points <literal>fspace(j) = x(j),j = 2, ..., n</literal>.
                                                        </para>
                                                    </listitem>
                                                </varlistentry>
                                                <varlistentry>
                                                    <term>= 2
                                                    </term>
                                                    <listitem>
                                                        <para>
                                                            if the initial mesh is supplied by the user as with <literal>ipar(8)=1</literal>, and
                                                            in addition no adaptive mesh selection is to be done.
                                                        </para>
                                                    </listitem>
                                                </varlistentry>
                                            </variablelist>
                                        </listitem>
                                    </varlistentry>
                                </variablelist>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>iguess: ipar(9)</term>
                            <listitem>
                                <variablelist>
                                    <varlistentry>
                                        <term>= 0</term>
                                        <listitem>
                                            <para>if no initial guess for the solution is
                                                provided.
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= 1</term>
                                        <listitem>
                                            <para>if an initial guess is provided by the user
                                                through the argument <literal>guess</literal>.
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= 2</term>
                                        <listitem>
                                            <para>if an initial mesh and approximate solution
                                                coefficients are provided by the user in <literal>fspace</literal> (the
                                                former and new mesh are the same).
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= 3</term>
                                        <listitem>
                                            <para>if a former mesh and approximate solution
                                                coefficients are provided by the user in <literal>fspace</literal>, and the
                                                new mesh is to be taken twice as coarse; i.e. every
                                                second point from the former mesh.
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= 4</term>
                                        <listitem>
                                            <para>if in addition to a former initial mesh and
                                                approximate solution coefficients, a new mesh is
                                                provided in <literal>fspace</literal> as well (see description of output
                                                for further details on iguess = 2, 3 and 4).
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                </variablelist>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>ireg: ipar(10)</term>
                            <listitem>
                                <variablelist>
                                    <varlistentry>
                                        <term>= 0</term>
                                        <listitem>
                                            <para>if the problem is regular</para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= 1</term>
                                        <listitem>
                                            <para>
                                                if the first relaxation factor is equal to <literal>ireg</literal>, and
                                                the nonlinear iteration does not rely on past convergence
                                                (use for an extra-sensitive nonlinear problem only)
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                    <varlistentry>
                                        <term>= 2</term>
                                        <listitem>
                                            <para>if we are to return immediately upon (a) two
                                                successive nonconvergences, or (b) after obtaining an error
                                                estimate for the first time.
                                            </para>
                                        </listitem>
                                    </varlistentry>
                                </variablelist>
                            </listitem>
                        </varlistentry>
                        <varlistentry>
                            <term>nfxpnt: ipar(11)</term>
                            <listitem>
                                <para>Gives the number of fixed points in the mesh other than
                                    <literal>x_low</literal> and <literal>x_up</literal> (the
                                    dimension of <literal>fixpnt</literal>).
                                    <literal>ipar(11)</literal> must be set to the dimension of
                                    the <literal>fixpnt</literal> argument or to
                                    <literal>0</literal>. In the latter case the actual value will
                                    automatically be set to
                                    <literal>size(fixpnt,'*')</literal>.
                                </para>
                            </listitem>
                        </varlistentry>
                    </variablelist>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>ltol</term>
                <listitem>
                    <para>
                        an array of dimension <literal>ntol=ipar(4)</literal>.
                        <literal>ltol(j) = l</literal> specifies that the <literal>j</literal>-th tolerance in
                        the <literal>tol</literal> array controls the error in the <literal>l</literal>-th
                        component of
                        <inlinemediaobject>
                            <imageobject>
                                <imagedata>
                                    <mml:math>
                                        <mml:semantics>
                                            <mml:mi>z</mml:mi>
                                            <mml:mrow>
                                                <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>u</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                            </mml:mrow>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        .
                        It is also required that:
                    </para>
                    <para>
                        <literal>1 &lt;= ltol(1) &lt; ltol(2) &lt; ... &lt; ltol(ntol)
                            &lt;= M
                        </literal>
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>tol</term>
                <listitem>
                    <para>
                        an array of dimension <literal>ntol=ipar(4)</literal>.
                    </para>
                    <para>
                        <literal>tol(j)</literal> is the error tolerance on the
                        <literal>ltol(j)</literal>-th component of
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                            <imageobject>
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                                        <mml:semantics>
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                                </imagedata>
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                        </inlinemediaobject>
                        . Thus, the code attempts to satisfy
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                                    <mml:math>
                                        <mml:semantics>
                                            <mml:mrow>
                                                <mml:mrow>
                                                    <mml:mfenced mml:close="∣" mml:open="∣">
                                                        <mml:msub>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                                <mml:mrow>
                                                                    <mml:mi>z</mml:mi>
                                                                    <mml:mrow>
                                                                        <mml:mrow>
                                                                            <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>v</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                                        </mml:mrow>
                                                                        <mml:mo mml:stretchy="false">−</mml:mo><mml:mi>z</mml:mi>
                                                                    </mml:mrow>
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                                                                    </mml:mrow>
                                                                </mml:mrow>
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                                                            </mml:mrow>
                                                            <mml:mrow>
                                                                <mml:mi mml:fontstyle="italic">ltol</mml:mi>
                                                                <mml:mrow>
                                                                    <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>j</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                                </mml:mrow>
                                                            </mml:mrow>
                                                        </mml:msub>
                                                    </mml:mfenced>
                                                    <mml:mo mml:stretchy="false">≤</mml:mo><mml:mi mml:fontstyle="italic">tol</mml:mi>
                                                </mml:mrow>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>j</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">⋅</mml:mo>
                                                        <mml:mfenced mml:close="∣" mml:open="∣">
                                                            <mml:msub>
                                                                <mml:mrow>
                                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                                    <mml:mrow>
                                                                        <mml:mi>z</mml:mi>
                                                                        <mml:mrow>
                                                                            <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>u</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                                        </mml:mrow>
                                                                    </mml:mrow>
                                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                                </mml:mrow>
                                                                <mml:mrow>
                                                                    <mml:mi mml:fontstyle="italic">ltol</mml:mi>
                                                                    <mml:mrow>
                                                                        <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>j</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                                    </mml:mrow>
                                                                </mml:mrow>
                                                            </mml:msub>
                                                        </mml:mfenced>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">+</mml:mo><mml:mi mml:fontstyle="italic">tol</mml:mi>
                                                </mml:mrow>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>j</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mi>,</mml:mi><mml:mi mml:fontstyle="normal">for</mml:mi>
                                                <mml:mrow>
                                                    <mml:mi>j</mml:mi><mml:mo mml:stretchy="false">=</mml:mo><mml:mn>1</mml:mn>
                                                </mml:mrow>
                                                <mml:mi mml:fontstyle="normal">:</mml:mi><mml:mi mml:fontstyle="normal">ntol</mml:mi>
                                            </mml:mrow>
                                            <mml:annotation mml:encoding="StarMath 5.0">abs(z(v)-z(u))_{ltol(j)}
                                                &lt;= tol(j) cdot abs(z(u))_{ltol(j)} + tol(j), for
                                                j=1:ntol
                                            </mml:annotation>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        on each subinterval
                    </para>
                    <para>
                        where
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                                        <mml:semantics>
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                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        is the approximate solution vector and
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                            <imageobject>
                                <imagedata>
                                    <mml:math>
                                        <mml:semantics>
                                            <mml:mi>u</mml:mi>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        is the
                        exact solution (unknown).
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>fixpnt</term>
                <listitem>
                    <para>
                        an array of dimension <literal>nfxpnt=ipar(11)</literal>. It
                        contains the points, other than <literal>x_low</literal> and
                        <literal>x_up</literal>, which are to be included in every mesh. The
                        code requires that all side condition points other than
                        <literal>x_low</literal> and <literal>x_up</literal> (see
                        description of <literal>zeta</literal>) be included as fixed points in
                        <literal>fixpnt</literal>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>fsub</term>
                <listitem>
                    <para>
                        an <link linkend="external">external</link> used to evaluate
                        the column vector <literal>f=</literal>
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                            <imageobject>
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                                                    </mml:mrow>
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                                                        <mml:mi>f</mml:mi><mml:mn>2</mml:mn>
                                                    </mml:msub>
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                                                            </mml:mrow>
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                                                        <mml:mi>f</mml:mi><mml:mi>N</mml:mi>
                                                    </mml:msub>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mi>x</mml:mi><mml:mi>,</mml:mi><mml:mi>z</mml:mi>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                                <mml:mrow>
                                                                    <mml:mi>u</mml:mi>
                                                                    <mml:mrow>
                                                                        <mml:mo mml:stretchy="false">(</mml:mo><mml:mi>x</mml:mi><mml:mo mml:stretchy="false">)</mml:mo>
                                                                    </mml:mrow>
                                                                </mml:mrow>
                                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                                            </mml:mrow>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                </mml:mrow>
                                                <mml:mo mml:stretchy="false">]</mml:mo>
                                            </mml:mrow>
                                            <mml:annotation mml:encoding="StarMath 5.0">[f_1(x,z(u(x)));
                                                f_2(x,z(u(x))),dotsaxis,
                                                f_N(x,z(u(x)))]
                                            </mml:annotation>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        for any <literal>x</literal> such as <literal>x_low</literal> &lt;= <literal>x</literal> &lt;= <literal>x_up</literal>
                        and for any <literal>z=z(u(x))</literal> (see description below).
                    </para>
                    <para>The external must have the headings:</para>
                    <itemizedlist>
                        <listitem>
                            <para>In Fortran the calling sequence must be:</para>
                            <screen><![CDATA[
subroutine fsub(x,zu,f)
double precision zu(*), f(*),x
]]></screen>
                        </listitem>
                        <listitem>
                            <para>In C the function prototype must be:</para>
                            <screen><![CDATA[
void fsub(double *x, double *zu, double *f)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>And in Scilab:</para>
                            <screen><![CDATA[
function f = fsub(x,zu,parameters)
]]></screen>
                        </listitem>
                    </itemizedlist>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>dfsub</term>
                <listitem>
                    <para>
                        an <link linkend="external">external</link> used to evaluate
                        the Jacobian of <literal>f(x,z(u))</literal> at a point <literal>x</literal>. Where
                        <literal>z(u(x))</literal> is defined as for <literal>fsub</literal>
                        and the <literal>N</literal> by <literal>M</literal> array <literal>df</literal>
                        should be filled by the partial derivatives of <literal>f</literal>:
                    </para>
                    <informalequation>
                        <mediaobject>
                            <imageobject>
                                <imagedata align="center">
                                    <mml:math>
                                        <mml:semantics>
                                            <mml:mrow>
                                                <mml:mi mml:fontstyle="italic">df</mml:mi>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mi>i</mml:mi>
                                                            <mml:mi>,</mml:mi>
                                                            <mml:mi>j</mml:mi>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                    <mml:mfrac>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">∂</mml:mo>
                                                            <mml:msub>
                                                                <mml:mi>f</mml:mi>
                                                                <mml:mi>i</mml:mi>
                                                            </mml:msub>
                                                        </mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">∂</mml:mo>
                                                            <mml:msub>
                                                                <mml:mi>z</mml:mi>
                                                                <mml:mi>j</mml:mi>
                                                            </mml:msub>
                                                        </mml:mrow>
                                                    </mml:mfrac>
                                                </mml:mrow>
                                                <mml:mtext> for
                                                </mml:mtext>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="true">{</mml:mo>
                                                    <mml:mtable>
                                                        <mml:mtr>
                                                            <mml:mrow>
                                                                <mml:mrow>
                                                                    <mml:mi>i</mml:mi>
                                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mi mml:fontstyle="normal">:</mml:mi>
                                                                <mml:mi mml:fontstyle="italic">N</mml:mi>
                                                            </mml:mrow>
                                                        </mml:mtr>
                                                        <mml:mtr>
                                                            <mml:mrow>
                                                                <mml:mrow>
                                                                    <mml:mi>j</mml:mi>
                                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mi mml:fontstyle="normal">:</mml:mi>
                                                                <mml:mi mml:fontstyle="italic">M</mml:mi>
                                                            </mml:mrow>
                                                        </mml:mtr>
                                                    </mml:mtable>
                                                </mml:mrow>
                                            </mml:mrow>
                                            <mml:annotation mml:encoding="StarMath 5.0">df(i,j)= {partial{f_i}} over
                                                {partial{z_j}} ~ for ~ left lbrace binom{i=1:N}{j=1:M} right
                                                none
                                            </mml:annotation>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </mediaobject>
                    </informalequation>
                    <para>The external must have the headings:</para>
                    <itemizedlist>
                        <listitem>
                            <para>In Fortran the calling sequence must be:</para>
                            <screen><![CDATA[
subroutine dfsub(x,zu,df)
double precision zu(*), df(*),x
]]></screen>
                        </listitem>
                        <listitem>
                            <para>In C the function prototype must be:</para>
                            <screen><![CDATA[
void dfsub(double *x, double *zu, double *df)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>And in Scilab:</para>
                            <screen><![CDATA[
function df = dfsub(x,zu,parameters)
]]></screen>
                        </listitem>
                    </itemizedlist>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>gsub</term>
                <listitem>
                    <para>
                        an <link linkend="external">external</link> used to evaluate
                        <inlinemediaobject>
                            <imageobject>
                                <imagedata>
                                    <mml:math scilab:localized="false">
                                        <mml:semantics>
                                            <mml:mrow>
                                                <mml:msub>
                                                    <mml:mi>g</mml:mi><mml:mi>i</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                    <mml:mrow>
                                                        <mml:msub>
                                                            <mml:mo mml:stretchy="false">ζ</mml:mo><mml:mi>i</mml:mi>
                                                        </mml:msub>
                                                        <mml:mi>,</mml:mi><mml:mi>z</mml:mi>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mi>u</mml:mi>
                                                                <mml:mrow>
                                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                                    <mml:msub>
                                                                        <mml:mo mml:stretchy="false">ζ</mml:mo><mml:mi>i</mml:mi>
                                                                    </mml:msub>
                                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                                </mml:mrow>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                </mml:mrow>
                                            </mml:mrow>
                                            <mml:annotation mml:encoding="StarMath 5.0">g_i(%zeta_i,z(u(%zeta_i)))</mml:annotation>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        given z=
                        <inlinemediaobject>
                            <imageobject>
                                <imagedata>
                                    <mml:math scilab:localized="false">
                                        <mml:semantics>
                                            <mml:mrow>
                                                <mml:mi>z</mml:mi>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                    <mml:mrow>
                                                        <mml:mi>u</mml:mi>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:msub>
                                                                <mml:mo mml:stretchy="false">ζ</mml:mo><mml:mi>i</mml:mi>
                                                            </mml:msub>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                </mml:mrow>
                                            </mml:mrow>
                                            <mml:annotation mml:encoding="StarMath 5.0">z(u(%zeta_i))</mml:annotation>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </inlinemediaobject>
                        <literal>z = zeta(i)</literal> for
                        <literal>1&lt;=i&lt;=M.</literal>
                    </para>
                    <para>The external must have the headings:</para>
                    <itemizedlist>
                        <listitem>
                            <para>In Fortran the calling sequence must be:</para>
                            <screen><![CDATA[
subroutine gsub(i,zu,g)
double precision zu(*), g(*)
integer i
]]></screen>
                        </listitem>
                        <listitem>
                            <para>In C the function prototype must be:</para>
                            <screen><![CDATA[
void gsub(int *i, double *zu, double *g)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>And in Scilab:</para>
                            <screen><![CDATA[
function g = gsub(i,zu,parameters)
]]></screen>
                            <para>
                                Note that in contrast to <literal>f</literal> in <literal>fsub</literal>, here only one value per call is returned in <literal>g</literal>.
                            </para>
                        </listitem>
                    </itemizedlist>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>dgsub</term>
                <listitem>
                    <para>
                        an <link linkend="external">external</link> used to evaluate
                        the <literal>i</literal>-th row of the Jacobian of <literal>g(x,u(x))</literal>. Where
                        <literal>z(u)</literal> is as for <literal>fsub</literal>, <literal>i</literal> as for
                        <literal>gsub</literal> and the <literal>M</literal>-vector <literal>dg</literal> should
                        be filled with the partial derivatives of <literal>g</literal>, viz, for a particular call one
                        calculates
                    </para>
                    <informalequation>
                        <mediaobject>
                            <imageobject>
                                <imagedata align="center">
                                    <mml:math>
                                        <mml:semantics>
                                            <mml:mrow>
                                                <mml:mi mml:fontstyle="italic">dg</mml:mi>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mi>i</mml:mi>
                                                            <mml:mi>,</mml:mi>
                                                            <mml:mi>j</mml:mi>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                    <mml:mfrac>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">∂</mml:mo>
                                                            <mml:msub>
                                                                <mml:mi>g</mml:mi>
                                                                <mml:mi>i</mml:mi>
                                                            </mml:msub>
                                                        </mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">∂</mml:mo>
                                                            <mml:msub>
                                                                <mml:mi>z</mml:mi>
                                                                <mml:mi>j</mml:mi>
                                                            </mml:msub>
                                                        </mml:mrow>
                                                    </mml:mfrac>
                                                </mml:mrow>
                                                <mml:mtext> for
                                                </mml:mtext>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="true">{</mml:mo>
                                                    <mml:mtable>
                                                        <mml:mtr>
                                                            <mml:mrow>
                                                                <mml:mrow>
                                                                    <mml:mi>i</mml:mi>
                                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mi mml:fontstyle="normal">:</mml:mi>
                                                                <mml:mi mml:fontstyle="italic">M</mml:mi>
                                                            </mml:mrow>
                                                        </mml:mtr>
                                                        <mml:mtr>
                                                            <mml:mrow>
                                                                <mml:mrow>
                                                                    <mml:mi>j</mml:mi>
                                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mi mml:fontstyle="normal">:</mml:mi>
                                                                <mml:mi mml:fontstyle="italic">M</mml:mi>
                                                            </mml:mrow>
                                                        </mml:mtr>
                                                    </mml:mtable>
                                                </mml:mrow>
                                            </mml:mrow>
                                            <mml:annotation mml:encoding="StarMath 5.0">dg(i,j)= {partial{g_i}} over
                                                {partial{z_j}} ~ for ~ left lbrace binom{i=1:M}{j=1:M} right
                                                none
                                            </mml:annotation>
                                        </mml:semantics>
                                    </mml:math>
                                </imagedata>
                            </imageobject>
                        </mediaobject>
                    </informalequation>
                    <para>The external must have the headings:</para>
                    <itemizedlist>
                        <listitem>
                            <para>In Fortran the calling sequence must be:</para>
                            <screen><![CDATA[
subroutine dgsub(i,zu,dg)
double precision zu(*), dg(*)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>In C the function prototype must be</para>
                            <screen><![CDATA[
void dgsub(int *i, double *zu, double *dg)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>And in Scilab </para>
                            <screen><![CDATA[
function dg = dgsub(i,zu,parameters)
]]></screen>
                        </listitem>
                    </itemizedlist>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>guess</term>
                <listitem>
                    <para>
                        An <link linkend="external">external</link> used to evaluate
                        the initial approximation for <literal>z(u(x))</literal> and
                        <literal>dmval(u(x))</literal> the vector of the <literal>mj</literal>-th derivatives
                        of <literal>u(x)</literal>. Note that this subroutine is used only
                        if <literal>ipar(9) = 1</literal>, and then all <literal>M</literal>
                        components of  <literal>zu</literal> and <literal>N</literal> components of <literal>dmval</literal> should be computed for
                        any <literal>x</literal> such as <literal>x_low</literal> &lt;= <literal>x</literal> &lt;= <literal>x_up</literal>.
                    </para>
                    <para>The external must have the headings:</para>
                    <itemizedlist>
                        <listitem>
                            <para>In Fortran the calling sequence must be:</para>
                            <screen><![CDATA[
subroutine guess(x,zu,dmval)
double precision x,z(*), dmval(*)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>In C the function prototype must be</para>
                            <screen><![CDATA[
void fsub(double *x, double *zu, double *dmval)
]]></screen>
                        </listitem>
                        <listitem>
                            <para>And in Scilab </para>
                            <screen><![CDATA[
function [dmval,zu] = fsub(x,parameters)
]]></screen>
                        </listitem>
                    </itemizedlist>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>&lt;optional_args&gt;</term>
                <listitem>
                    <para>It should be either:</para>
                    <itemizedlist>
                        <listitem>
                            <para>any left part of the ordered sequence of values:
                                <literal>guess, dfsub, dgsub, fixpnt, ndimf, ndimi, ltol, tol,
                                    ntol,nonlin, collpnt, subint, iprint, ireg, ifail
                                </literal>
                            </para>
                        </listitem>
                        <listitem>
                            <para>
                                or any sequence of <literal>arg_name=argvalue</literal>
                                with <literal>arg_name</literal> in: <literal>guess</literal>,
                                <literal>dfsub</literal>, <literal>dgsub</literal>,
                                <literal>fixpnt</literal>, <literal>ndimf</literal>,
                                <literal>ndimi</literal>, <literal>ltol</literal>,
                                <literal>tol</literal>, <literal>ntol</literal>,
                                <literal>nonlin</literal>, <literal>collpnt</literal>,
                                <literal>subint</literal>, <literal>iprint</literal>,
                                <literal>ireg</literal>, <literal>ifail</literal>
                            </para>
                        </listitem>
                    </itemizedlist>
                    <para>
                        where all these arguments excepted <literal>ifail</literal> are
                        described above. <literal>ifail</literal> can be used to display the
                        bvode call corresponding to the selected optional arguments. If
                        <literal>guess</literal> is given <literal>iguess</literal> is set to
                        1
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsection>
    <refsection>
        <title>Description</title>
        <para>These functions solve a multi-point boundary value problem for a
            mixed order system of ode-s given by
        </para>
        <informalequation>
            <mediaobject>
                <imageobject>
                    <imagedata align="left">
                        <mml:math>
                            <mml:semantics>
                                <mml:mrow>
                                    <mml:mo mml:stretchy="true">{</mml:mo>
                                    <mml:mtable>
                                        <mml:mtr>
                                            <mml:mrow>
                                                <mml:mrow>
                                                    <mml:msubsup>
                                                        <mml:mi>u</mml:mi>
                                                        <mml:mi>i</mml:mi>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:msub>
                                                                <mml:mi>m</mml:mi>
                                                                <mml:mi>i</mml:mi>
                                                            </mml:msub>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:msubsup>
                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                    <mml:msub>
                                                        <mml:mi>f</mml:mi>
                                                        <mml:mi>i</mml:mi>
                                                    </mml:msub>
                                                </mml:mrow>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                    <mml:mrow>
                                                        <mml:mi>x</mml:mi>
                                                        <mml:mi>,</mml:mi>
                                                        <mml:mi>z</mml:mi>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mi>u</mml:mi>
                                                                <mml:mrow>
                                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                                    <mml:mi>x</mml:mi>
                                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                                </mml:mrow>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mi/>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="true">{</mml:mo>
                                                    <mml:mtable>
                                                        <mml:mtr>
                                                            <mml:mrow>
                                                                <mml:mrow>
                                                                    <mml:mi>i</mml:mi>
                                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mi mml:fontstyle="normal">:</mml:mi>
                                                                <mml:mi>N</mml:mi>
                                                            </mml:mrow>
                                                        </mml:mtr>
                                                        <mml:mtr>
                                                            <mml:mrow>
                                                                <mml:mi>x</mml:mi>
                                                                <mml:mo mml:stretchy="false">∈</mml:mo>
                                                                <mml:mfenced mml:close="[" mml:open="]">
                                                                    <mml:mrow>
                                                                        <mml:msub>
                                                                            <mml:mi>x</mml:mi>
                                                                            <mml:mi>l</mml:mi>
                                                                        </mml:msub>
                                                                        <mml:mi>,</mml:mi>
                                                                        <mml:msub>
                                                                            <mml:mi>x</mml:mi>
                                                                            <mml:mi>u</mml:mi>
                                                                        </mml:msub>
                                                                    </mml:mrow>
                                                                </mml:mfenced>
                                                            </mml:mrow>
                                                        </mml:mtr>
                                                    </mml:mtable>
                                                </mml:mrow>
                                            </mml:mrow>
                                        </mml:mtr>
                                        <mml:mtr>
                                            <mml:mi/>
                                        </mml:mtr>
                                        <mml:mtr>
                                            <mml:mrow>
                                                <mml:msub>
                                                    <mml:mi>g</mml:mi>
                                                    <mml:mi>j</mml:mi>
                                                </mml:msub>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mrow>
                                                            <mml:msub>
                                                                <mml:mo mml:stretchy="false">ζ</mml:mo>
                                                                <mml:mi>j</mml:mi>
                                                            </mml:msub>
                                                            <mml:mi>,</mml:mi>
                                                            <mml:mi>z</mml:mi>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                                <mml:mrow>
                                                                    <mml:mi>u</mml:mi>
                                                                    <mml:mrow>
                                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                                        <mml:msub>
                                                                            <mml:mo mml:stretchy="false">ζ</mml:mo>
                                                                            <mml:mi>j</mml:mi>
                                                                        </mml:msub>
                                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                                    </mml:mrow>
                                                                </mml:mrow>
                                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                                            </mml:mrow>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                </mml:mrow>
                                                <mml:mi/>
                                                <mml:mrow>
                                                    <mml:mtext>,</mml:mtext>
                                                    <mml:mi>j</mml:mi>
                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                    <mml:mn>1</mml:mn>
                                                </mml:mrow>
                                                <mml:mi mml:fontstyle="normal">:</mml:mi>
                                                <mml:mi>M</mml:mi>
                                            </mml:mrow>
                                        </mml:mtr>
                                    </mml:mtable>
                                </mml:mrow>
                                <mml:annotation mml:encoding="StarMath 5.0">left lbrace
                                    stack{u_i^(m_i)=f_i(x,z(u(x))) ~~left lbrace { binom{i=1:N}{x
                                    in left ] a_l, a_u right [} } right none# `#
                                    g_j(%zeta_j,z(u(%zeta_j))) = 0~~j=1:M} right
                                    none
                                </mml:annotation>
                            </mml:semantics>
                        </mml:math>
                    </imagedata>
                </imageobject>
            </mediaobject>
        </informalequation>
        <para>where</para>
        <mediaobject>
            <imageobject>
                <imagedata align="left">
                    <mml:math>
                        <mml:semantics>
                            <mml:mrow>
                                <mml:mo mml:stretchy="true">{</mml:mo>
                                <mml:mtable>
                                    <mml:mtr>
                                        <mml:mrow>
                                            <mml:mi>M</mml:mi>
                                            <mml:mo mml:stretchy="false">=</mml:mo>
                                            <mml:mrow>
                                                <mml:munderover>
                                                    <mml:mo mml:stretchy="false">∑</mml:mo>
                                                    <mml:mrow>
                                                        <mml:mi>i</mml:mi>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>1</mml:mn>
                                                    </mml:mrow>
                                                    <mml:mi>N</mml:mi>
                                                </mml:munderover>
                                                <mml:msub>
                                                    <mml:mi>m</mml:mi>
                                                    <mml:mi>i</mml:mi>
                                                </mml:msub>
                                            </mml:mrow>
                                        </mml:mrow>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mi/>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mrow>
                                            <mml:mi>z</mml:mi>
                                            <mml:mrow>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">(</mml:mo>
                                                    <mml:mrow>
                                                        <mml:mi>u</mml:mi>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">)</mml:mo>
                                                </mml:mrow>
                                                <mml:mo mml:stretchy="false">=</mml:mo>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">[</mml:mo>
                                                    <mml:mrow>
                                                        <mml:msub>
                                                            <mml:mi>u</mml:mi>
                                                            <mml:mn>1</mml:mn>
                                                        </mml:msub>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:msubsup>
                                                            <mml:mi>u</mml:mi>
                                                            <mml:mn>1</mml:mn>
                                                            <mml:mn>1</mml:mn>
                                                        </mml:msubsup>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:mo mml:stretchy="false">⋯</mml:mo>
                                                        <mml:msubsup>
                                                            <mml:mi>u</mml:mi>
                                                            <mml:mn>1</mml:mn>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                                <mml:mrow>
                                                                    <mml:msub>
                                                                        <mml:mi>m</mml:mi>
                                                                        <mml:mn>1</mml:mn>
                                                                    </mml:msub>
                                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                                            </mml:mrow>
                                                        </mml:msubsup>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:mi/>
                                                        <mml:mo mml:stretchy="false">⋯</mml:mo>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:mi/>
                                                        <mml:msub>
                                                            <mml:mi>u</mml:mi>
                                                            <mml:mi>N</mml:mi>
                                                        </mml:msub>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:msubsup>
                                                            <mml:mi>u</mml:mi>
                                                            <mml:mi>N</mml:mi>
                                                            <mml:mn>1</mml:mn>
                                                        </mml:msubsup>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:mo mml:stretchy="false">⋯</mml:mo>
                                                        <mml:mi>;</mml:mi>
                                                        <mml:msubsup>
                                                            <mml:mi>u</mml:mi>
                                                            <mml:mi>N</mml:mi>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                                <mml:mrow>
                                                                    <mml:msub>
                                                                        <mml:mi>m</mml:mi>
                                                                        <mml:mi>N</mml:mi>
                                                                    </mml:msub>
                                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                                    <mml:mn>1</mml:mn>
                                                                </mml:mrow>
                                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                                            </mml:mrow>
                                                        </mml:msubsup>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">]</mml:mo>
                                                </mml:mrow>
                                            </mml:mrow>
                                        </mml:mrow>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mi/>
                                    </mml:mtr>
                                    <mml:mtr>
                                        <mml:mrow>
                                            <mml:mrow>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:msub>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mi>l</mml:mi>
                                                        </mml:msub>
                                                        <mml:mo mml:stretchy="false">≤</mml:mo>
                                                        <mml:msub>
                                                            <mml:mo mml:stretchy="false">ζ</mml:mo>
                                                            <mml:mn>1</mml:mn>
                                                        </mml:msub>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">≤</mml:mo>
                                                    <mml:mo mml:stretchy="false">⋯</mml:mo>
                                                </mml:mrow>
                                                <mml:mo mml:stretchy="false">≤</mml:mo>
                                                <mml:msub>
                                                    <mml:mo mml:stretchy="false">ζ</mml:mo>
                                                    <mml:mi>M</mml:mi>
                                                </mml:msub>
                                            </mml:mrow>
                                            <mml:mo mml:stretchy="false">≤</mml:mo>
                                            <mml:msub>
                                                <mml:mi>x</mml:mi>
                                                <mml:mi>u</mml:mi>
                                            </mml:msub>
                                        </mml:mrow>
                                    </mml:mtr>
                                </mml:mtable>
                            </mml:mrow>
                            <mml:annotation mml:encoding="StarMath 5.0">left lbrace stack
                                { M= sum from {i=1} to {N} m_i # ~# z(u(x)) =
                                [u_1(x);u_1^{1}(x);dotsaxis u_1^(m_1-1)(x);~ dotsaxis;
                                ~u_N(x);u_N^{1}(x);dotsaxis; u_N^(m_N-1)(x)]# ~# x_l &lt;=
                                %zeta_1 &lt;= dotsaxis &lt;= %zeta_M &lt;=x_u}right
                                none
                            </mml:annotation>
                        </mml:semantics>
                    </mml:math>
                </imagedata>
            </imageobject>
        </mediaobject>
        <para>
            The argument <literal>zu</literal> used by the external functions
            and returned by <literal>bvode</literal> is the column vector formed by
            the components of <literal>z(u(x))</literal> for a given <literal>x</literal>.
        </para>
        <para>
            The method used to approximate the solution <literal>u</literal> is collocation at
            gaussian points, requiring <literal>m(i)-1</literal> continuous derivatives in the <literal>i</literal>-th
            component, <literal>i = 1:N</literal>. here, <literal>k</literal> is the number of collocation points (stages)
            per subinterval and is chosen such that <emphasis>k ≥ max(m(i))</emphasis>.
            A runge-kutta-monomial solution representation is utilized.
        </para>
    </refsection>
    <refsection>
        <title>Examples</title>
        <para>The first two problems below are taken from the paper [1] of the
            Bibliography.
        </para>
        <itemizedlist>
            <listitem>
                <para>
                    <emphasis role="bold">The problem 1</emphasis> describes a
                    uniformly loaded beam of variable stiffness, simply supported at both
                    end.
                </para>
                <para>It may be defined as follow :</para>
                <para>Solve the fourth order differential equation:</para>
                <mediaobject>
                    <imageobject>
                        <imagedata align="left">
                            <mml:math>
                                <mml:semantics>
                                    <mml:mrow>
                                        <mml:mfrac>
                                            <mml:msup>
                                                <mml:mi>d</mml:mi>
                                                <mml:mn>4</mml:mn>
                                            </mml:msup>
                                            <mml:mrow>
                                                <mml:mi>d</mml:mi>
                                                <mml:msup>
                                                    <mml:mi>x</mml:mi>
                                                    <mml:mn>4</mml:mn>
                                                </mml:msup>
                                            </mml:mrow>
                                        </mml:mfrac>
                                        <mml:mi>u</mml:mi>
                                        <mml:mrow>
                                            <mml:mrow>
                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                <mml:mi>x</mml:mi>
                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo mml:stretchy="false">=</mml:mo>
                                            <mml:mfrac>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mn>1</mml:mn>
                                                        <mml:mo mml:stretchy="false">−</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mrow>
                                                                <mml:mn>6</mml:mn>
                                                                <mml:mo mml:stretchy="false">.</mml:mo>
                                                                <mml:msup>
                                                                    <mml:mi>x</mml:mi>
                                                                    <mml:mn>2</mml:mn>
                                                                </mml:msup>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">.</mml:mo>
                                                            <mml:mfrac>
                                                                <mml:msup>
                                                                    <mml:mi>d</mml:mi>
                                                                    <mml:mn>3</mml:mn>
                                                                </mml:msup>
                                                                <mml:mrow>
                                                                    <mml:mi>d</mml:mi>
                                                                    <mml:msup>
                                                                        <mml:mi>x</mml:mi>
                                                                        <mml:mn>3</mml:mn>
                                                                    </mml:msup>
                                                                </mml:mrow>
                                                            </mml:mfrac>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mi>u</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">−</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mrow>
                                                                <mml:mn>6</mml:mn>
                                                                <mml:mo mml:stretchy="false">.</mml:mo>
                                                                <mml:mi>x</mml:mi>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">.</mml:mo>
                                                            <mml:mfrac>
                                                                <mml:msup>
                                                                    <mml:mi>d</mml:mi>
                                                                    <mml:mn>2</mml:mn>
                                                                </mml:msup>
                                                                <mml:mrow>
                                                                    <mml:mi>d</mml:mi>
                                                                    <mml:msup>
                                                                        <mml:mi>x</mml:mi>
                                                                        <mml:mn>2</mml:mn>
                                                                    </mml:msup>
                                                                </mml:mrow>
                                                            </mml:mfrac>
                                                        </mml:mrow>
                                                    </mml:mrow>
                                                    <mml:mi>u</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mi>x</mml:mi>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                </mml:mrow>
                                                <mml:msup>
                                                    <mml:mi>x</mml:mi>
                                                    <mml:mn>3</mml:mn>
                                                </mml:msup>
                                            </mml:mfrac>
                                        </mml:mrow>
                                    </mml:mrow>
                                    <mml:annotation mml:encoding="StarMath 5.0">d^4 over {d
                                        x^4} u(x)={1 -6*x^2*{{d^3} over {d x^3}} u(x)-6*x*{{d^2}
                                        over {d x^2}} u(x)} over x^3
                                    </mml:annotation>
                                </mml:semantics>
                            </mml:math>
                        </imagedata>
                    </imageobject>
                </mediaobject>
                <para>Subjected to the boundary conditions:</para>
                <mediaobject>
                    <imageobject>
                        <imagedata align="left">
                            <mml:math>
                                <mml:semantics>
                                    <mml:mrow>
                                        <mml:mo mml:stretchy="true">{</mml:mo>
                                        <mml:mtable>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mi>u</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mn>1</mml:mn>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mfrac>
                                                        <mml:msup>
                                                            <mml:mi>d</mml:mi>
                                                            <mml:mn>2</mml:mn>
                                                        </mml:msup>
                                                        <mml:mrow>
                                                            <mml:mi>d</mml:mi>
                                                            <mml:msup>
                                                                <mml:mi>x</mml:mi>
                                                                <mml:mn>2</mml:mn>
                                                            </mml:msup>
                                                        </mml:mrow>
                                                    </mml:mfrac>
                                                    <mml:mi>u</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mi>x</mml:mi>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mn>1</mml:mn>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mi>u</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mn>2</mml:mn>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mfrac>
                                                        <mml:msup>
                                                            <mml:mi>d</mml:mi>
                                                            <mml:mn>2</mml:mn>
                                                        </mml:msup>
                                                        <mml:mrow>
                                                            <mml:mi>d</mml:mi>
                                                            <mml:msup>
                                                                <mml:mi>x</mml:mi>
                                                                <mml:mn>2</mml:mn>
                                                            </mml:msup>
                                                        </mml:mrow>
                                                    </mml:mfrac>
                                                    <mml:mi>u</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mi>x</mml:mi>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mn>2</mml:mn>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                        </mml:mtable>
                                    </mml:mrow>
                                    <mml:annotation mml:encoding="StarMath 5.0">left lbrace
                                        stack{ u(1)=0# {{d^2} over {d x^2}} u(x)(1)=0# u(2)=0#
                                        {{d^2} over {d x^2}} u(x)(2)=0} right
                                        none
                                    </mml:annotation>
                                </mml:semantics>
                            </mml:math>
                        </imagedata>
                    </imageobject>
                </mediaobject>
                <para>The exact solution of this problem is known to be:</para>
                <mediaobject>
                    <imageobject>
                        <imagedata align="left">
                            <mml:math>
                                <mml:semantics>
                                    <mml:mrow>
                                        <mml:mi>u</mml:mi>
                                        <mml:mrow>
                                            <mml:mrow>
                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                <mml:mi>x</mml:mi>
                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo mml:stretchy="false">=</mml:mo>
                                            <mml:mfrac>
                                                <mml:mn>1</mml:mn>
                                                <mml:mn>4</mml:mn>
                                            </mml:mfrac>
                                        </mml:mrow>
                                        <mml:mrow>
                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                            <mml:mrow>
                                                <mml:mn>10</mml:mn>
                                                <mml:mi/>
                                                <mml:mi>log</mml:mi>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mn>2</mml:mn>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                    <mml:mn>3</mml:mn>
                                                </mml:mrow>
                                            </mml:mrow>
                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                        </mml:mrow>
                                        <mml:mi/>
                                        <mml:mrow>
                                            <mml:mrow>
                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                <mml:mrow>
                                                    <mml:mn>1</mml:mn>
                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                    <mml:mi>x</mml:mi>
                                                </mml:mrow>
                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                            </mml:mrow>
                                            <mml:mo mml:stretchy="false">+</mml:mo>
                                            <mml:mfrac>
                                                <mml:mn>1</mml:mn>
                                                <mml:mn>2</mml:mn>
                                            </mml:mfrac>
                                        </mml:mrow>
                                        <mml:mrow>
                                            <mml:mo mml:stretchy="false">[</mml:mo>
                                            <mml:mrow>
                                                <mml:mfrac>
                                                    <mml:mn>1</mml:mn>
                                                    <mml:mi>x</mml:mi>
                                                </mml:mfrac>
                                                <mml:mo mml:stretchy="false">+</mml:mo>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mo mml:stretchy="false">(</mml:mo>
                                                        <mml:mrow>
                                                            <mml:mn>3</mml:mn>
                                                            <mml:mo mml:stretchy="false">+</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">)</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mi/>
                                                    <mml:mi>log</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mi>x</mml:mi>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">−</mml:mo>
                                                        <mml:mi>x</mml:mi>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mrow>
                                            <mml:mo mml:stretchy="false">]</mml:mo>
                                        </mml:mrow>
                                    </mml:mrow>
                                    <mml:annotation mml:encoding="StarMath 5.0">u(x)=1 over 4
                                        (10`log(2)-3)`(1-x)+ {1 over 2} [ {1 over x} + {(3+x) `
                                        log(x)-x}]
                                    </mml:annotation>
                                </mml:semantics>
                            </mml:math>
                        </imagedata>
                    </imageobject>
                </mediaobject>
                <programlisting role="example"><![CDATA[
N = 1; // just one differential equation
m = 4; // a fourth order  differential equation
M = sum(m);

x_low = 1;
x_up = 2; // the x limits
zeta = [x_low,x_low,x_up,x_up]; // two constraints (on the value of u and its second derivative) on each bound.

// The external functions
// These functions are called by the solver with zu=[u(x);u'(x);u''(x);u'''(x)]

// - The function which computes the right hand side of the differential equation
function f = fsub(x,zu)
    f = (1-6*x^2*zu(4)-6*x*zu(3))/x^3
endfunction

// - The function which computes the derivative of fsub with respect to zu
function df = dfsub(x,zu)
    df = [0,0,-6/x^2,-6/x]
endfunction

// - The function which computes the ith constraint for a given i
function g = gsub(i,zu),
  select i
  case 1 then  // x = zeta(1) = 1
    g = zu(1)  // u(1) = 0
  case 2 then  // x = zeta(2) = 1
    g = zu(3)  // u''(1) = 0
  case 3 then  // x = zeta(3) = 2
    g = zu(1)  // u(2) = 0
  case 4 then  // x = zeta(4) = 2
    g = zu(3)  // u''(2) = 0
  end
endfunction

// - The function which computes the derivative of gsub with respect to z
function dg = dgsub(i,z)
  select i
  case 1 then  // x = zeta(1) = 1
    dg = [1,0,0,0]
  case 2 then  // x = zeta(2) = 1
    dg = [0,0,1,0]
  case 3 then  // x = zeta(3) = 2
    dg = [1,0,0,0]
  case 4 then  // x = zeta(4) = 2
    dg = [0,0,1,0]
  end
endfunction

// - The function which computes the initial guess, unused here
function [zu,mpar] = guess(x)
    zu = 0;
    mpar = 0;
endfunction

// define the function which computes the exact value of u for a given x ( for testing purposes)
function zu = trusol(x)
  zu = 0*ones(4,1)
  zu(1) =  0.25*(10*log(2)-3)*(1-x) + 0.5 *( 1/x   + (3+x)*log(x) - x)
  zu(2) = -0.25*(10*log(2)-3)       + 0.5 *(-1/x^2 + (3+x)/x      + log(x) - 1)
  zu(3) = 0.5*( 2/x^3 + 1/x   - 3/x^2)
  zu(4) = 0.5*(-6/x^4 - 1/x/x + 6/x^3)
endfunction

fixpnt = []; // All boundary conditions are located at x_low and x_up

//      nonlin  collpnt n ntol ndimf  ndimi iprint iread iguess rstart nfxpnt
ipar = [0       0       1 2    2000   200   1      0     0      0      0   ]

ltol = [1,3];          // set tolerance control on zu(1) and zu(3)
tol = [1.e-11,1.e-11]; // set tolerance values for these two controls
xpoints = x_low:0.01:x_up;

zu = bvode(xpoints,N,m,x_low,x_up,zeta,ipar,ltol,tol,fixpnt,...
           fsub,dfsub,gsub,dgsub,guess)
// check the constraints
zu([1,3],[1 $]) // should be zero
plot(xpoints,zu(1,:)) // the evolution of the solution u
zu1 = [];
for x = xpoints
    zu1 = [zu1,trusol(x)];
end
norm(zu-zu1)
             ]]></programlisting>
            </listitem>
            <listitem>
                <para>
                    Same problem using <literal>bvodeS</literal> and an initial guess.
                </para>
                <programlisting role="no-scilab-exec"><![CDATA[
function [z,lhS] = zstart(x)
    z = zeros(5,1); z(5) = 1;
    lhS = [0;1];
endfunction
zu = bvode(xpoints, N, m, x_low,x_up, zeta, ltol=ltol,tol=tol, guess=zstart)
 ]]></programlisting>
            </listitem>
            <listitem>
                <para>
                    <emphasis role="bold">The problem 2</emphasis> describes the
                    small finite deformation of a thin shallow spherical cap of constant
                    thickness subject to a quadratically varying axisymmetric external pressure
                    distribution. Here <emphasis>φ</emphasis> is the meridian angle change of the
                    deformed shell and <emphasis>ψ</emphasis> is a stress function.
                    For <emphasis>ε = μ = 10<superscript>-3</superscript></emphasis>, two
                    different solutions may found depending on the starting point
                </para>
                <mediaobject>
                    <imageobject>
                        <imagedata align="left">
                            <mml:math>
                                <mml:semantics>
                                    <mml:mrow>
                                        <mml:mo mml:stretchy="true">{</mml:mo>
                                        <mml:mtable>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mfrac>
                                                        <mml:msup>
                                                            <mml:mo mml:stretchy="false">ε</mml:mo>
                                                            <mml:mn>4</mml:mn>
                                                        </mml:msup>
                                                        <mml:mo mml:stretchy="false">μ</mml:mo>
                                                    </mml:mfrac>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">φ</mml:mo>
                                                                <mml:mi>'</mml:mi>
                                                                <mml:mrow>
                                                                    <mml:mrow>
                                                                        <mml:mi>'</mml:mi>
                                                                        <mml:mo mml:stretchy="false">+</mml:mo>
                                                                        <mml:mfrac>
                                                                            <mml:mrow>
                                                                                <mml:mo mml:stretchy="false">φ</mml:mo>
                                                                                <mml:mi>'</mml:mi>
                                                                            </mml:mrow>
                                                                            <mml:mi>x</mml:mi>
                                                                        </mml:mfrac>
                                                                    </mml:mrow>
                                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                                    <mml:mfrac>
                                                                        <mml:mo mml:stretchy="false">φ</mml:mo>
                                                                        <mml:msup>
                                                                            <mml:mi>x</mml:mi>
                                                                            <mml:mn>2</mml:mn>
                                                                        </mml:msup>
                                                                    </mml:mfrac>
                                                                </mml:mrow>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">+</mml:mo>
                                                        <mml:mo mml:stretchy="false">ψ</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">(</mml:mo>
                                                                <mml:mrow>
                                                                    <mml:mn>1</mml:mn>
                                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                                    <mml:mfrac>
                                                                        <mml:mo mml:stretchy="false">φ</mml:mo>
                                                                        <mml:mi>x</mml:mi>
                                                                    </mml:mfrac>
                                                                </mml:mrow>
                                                                <mml:mo mml:stretchy="false">)</mml:mo>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">−</mml:mo>
                                                            <mml:mo mml:stretchy="false">φ</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">+</mml:mo>
                                                        <mml:mo mml:stretchy="false">γ</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mi>x</mml:mi>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mn>1</mml:mn>
                                                                <mml:mo mml:stretchy="false">−</mml:mo>
                                                                <mml:mfrac>
                                                                    <mml:msup>
                                                                        <mml:mi>x</mml:mi>
                                                                        <mml:mn>2</mml:mn>
                                                                    </mml:msup>
                                                                    <mml:mn>2</mml:mn>
                                                                </mml:mfrac>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">μ</mml:mo>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mo mml:stretchy="false">ψ</mml:mo>
                                                                <mml:mi>'</mml:mi>
                                                                <mml:mrow>
                                                                    <mml:mrow>
                                                                        <mml:mi>'</mml:mi>
                                                                        <mml:mo mml:stretchy="false">+</mml:mo>
                                                                        <mml:mfrac>
                                                                            <mml:mrow>
                                                                                <mml:mo mml:stretchy="false">ψ</mml:mo>
                                                                                <mml:mi>'</mml:mi>
                                                                            </mml:mrow>
                                                                            <mml:mi>x</mml:mi>
                                                                        </mml:mfrac>
                                                                    </mml:mrow>
                                                                    <mml:mo mml:stretchy="false">−</mml:mo>
                                                                    <mml:mfrac>
                                                                        <mml:mo mml:stretchy="false">ψ</mml:mo>
                                                                        <mml:msup>
                                                                            <mml:mi>x</mml:mi>
                                                                            <mml:mn>2</mml:mn>
                                                                        </mml:msup>
                                                                    </mml:mfrac>
                                                                </mml:mrow>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">−</mml:mo>
                                                        <mml:mo mml:stretchy="false">φ</mml:mo>
                                                    </mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">(</mml:mo>
                                                            <mml:mrow>
                                                                <mml:mn>1</mml:mn>
                                                                <mml:mo mml:stretchy="false">−</mml:mo>
                                                                <mml:mfrac>
                                                                    <mml:mo mml:stretchy="false">φ</mml:mo>
                                                                    <mml:mn>2x</mml:mn>
                                                                </mml:mfrac>
                                                            </mml:mrow>
                                                            <mml:mo mml:stretchy="false">)</mml:mo>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mn>0</mml:mn>
                                                        <mml:mo mml:stretchy="false">&lt;</mml:mo>
                                                        <mml:mi>x</mml:mi>
                                                    </mml:mrow>
                                                    <mml:mo mml:stretchy="false">&lt;</mml:mo>
                                                    <mml:mn>1</mml:mn>
                                                </mml:mrow>
                                            </mml:mtr>
                                        </mml:mtable>
                                    </mml:mrow>
                                    <mml:annotation mml:encoding="StarMath 5.0">left lbrace
                                        stack{{%epsilon^4} over %mu (%phi''+ {%phi'} over x
                                        -{%phi} over {x^2} ) +%psi (1- %phi over x ) -%phi+%gamma
                                        x(1-{x^2} over 2)=0# %mu(%psi''+{%psi'} over x-%psi over
                                        {x^2})-%phi(1-%phi over{2x})=0 # 0&lt;x&lt;1} right
                                        none
                                    </mml:annotation>
                                </mml:semantics>
                            </mml:math>
                        </imagedata>
                    </imageobject>
                </mediaobject>
                <para>Subject to the boundary conditions</para>
                <mediaobject>
                    <imageobject>
                        <imagedata align="left">
                            <mml:math>
                                <mml:semantics>
                                    <mml:mrow>
                                        <mml:mo mml:stretchy="true">{</mml:mo>
                                        <mml:mtable>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mo mml:stretchy="false">φ</mml:mo>
                                                    <mml:mo mml:stretchy="false">=</mml:mo>
                                                    <mml:mn>0</mml:mn>
                                                </mml:mrow>
                                            </mml:mtr>
                                            <mml:mtr>
                                                <mml:mrow>
                                                    <mml:mi>x</mml:mi>
                                                    <mml:mi/>
                                                    <mml:mo mml:stretchy="false">ψ</mml:mo>
                                                    <mml:mrow>
                                                        <mml:mi>'</mml:mi>
                                                        <mml:mo mml:stretchy="false">−</mml:mo>
                                                        <mml:mn>0.3</mml:mn>
                                                    </mml:mrow>
                                                    <mml:mrow>
                                                        <mml:mrow>
                                                            <mml:mo mml:stretchy="false">ψ</mml:mo>
                                                            <mml:mo mml:stretchy="false">+</mml:mo>
                                                            <mml:mn>0.7x</mml:mn>
                                                        </mml:mrow>
                                                        <mml:mo mml:stretchy="false">=</mml:mo>
                                                        <mml:mn>0</mml:mn>
                                                    </mml:mrow>
                                                </mml:mrow>
                                            </mml:mtr>
                                        </mml:mtable>
                                    </mml:mrow>
                                    <mml:annotation mml:encoding="StarMath 5.0">left lbrace
                                        stack{ %phi=0# x`%psi'-0.3%psi+0.7x=0} right
                                        none
                                    </mml:annotation>
                                </mml:semantics>
                            </mml:math>
                        </imagedata>
                    </imageobject>
                </mediaobject>
                <para>
                    for <literal>x=0</literal> and <literal>x=1</literal>
                </para>
                <programlisting role="example"><![CDATA[
N = 2;     // two differential equations
m = [2 2]; // each differential equation is of second  order
M = sum(m);

x_low = 0;x_up=1; // the x limits
zeta = [x_low,x_low, x_up x_up]; // two  constraints on each bound.

// The external functions
// These functions are called by the solver with zu=[u1(x);u1'(x);u2(x);u2'(x)]

// - The function which computes the right hand side of the differential equation
function f = fsub2(x,zu,eps,dmu,eps4mu,gam,xt),
   f = [zu(1)/x^2-zu(2)/x+(zu(1)-zu(3)*(1-zu(1)/x)-gam*x*(1-x^2/2))/eps4mu //phi''
        zu(3)/x^2-zu(4)/x+zu(1)*(1-zu(1)/(2*x))/dmu];//psi''
endfunction

// - The function which computes the derivative of fsub with respect to zu
function df = dfsub2(x,zu,eps,dmu,eps4mu,gam,xt),
    df = [1/x^2+(1+zu(3)/x)/eps4mu, -1/x, -(1-zu(1)/x)/eps4mu, 0
         (1-zu(1)/x)/dmu             0    1/x^2              -1/x];
endfunction

// - The function which computes the ith constraint for a given i
function g = gsub2(i,zu),
  select i
  case 1 then  // x = zeta(1) = 0
    g = zu(1)  // u(0) = 0
  case 2 then  // x = zeta(2) = 0
    g = -0.3*zu(3) // x*psi'-0.3*psi+0.7x = 0
  case 3 then  // x = zeta(3) = 1
    g = zu(1)  // u(1) = 0
  case 4 then  // x = zeta(4) = 1
    g = 1*zu(4)-0.3*zu(3)+0.7*1 // x*psi'-0.3*psi+0.7x = 0
  end
endfunction

// - The function which computes the derivative of gsub with respect to z
function dg = dgsub2(i,z)
  select i
  case 1 then  // x = zeta(1) = 1
    dg = [1,0,0,0]
  case 2 then  // x = zeta(2) = 1
    dg = [0,0,-0.3,0]
  case 3 then  // x = zeta(3) = 2
    dg = [1,0,0,0]
  case 4 then  // x = zeta(4) = 2
    dg = [0,0,-0.3,1]
  end
endfunction

[gam, eps, dmu] = (1.1, 1d-3, 1d-3);
eps4mu = eps^4/dmu
xt = sqrt(2*(gam-1)/gam)

fixpnt = []; // All boundary conditions are located at x_low and x_up
collpnt = 4;
nsizef = 4 + 3*M + (5+collpnt*N)*(collpnt*N+M)+(2*M-2)*2*M ;
nsizei = 3 + collpnt*N+M;
nmax = 200;
//      nonlin  collpnt n  ntol  ndimf        ndimi       iprint iread iguess rstart nfxpnt
ipar = [1       collpnt 10  4   nmax*nsizef  nmax*nsizei   -1      0     0      0      0   ];

ltol = 1:4; // set tolerance control on zu(1), zu(2), zu(3) and zu(4)
tol = [1.e-5,1.e-5,1.e-5,1.e-5]; // set tolreance values for these four controls
xpoints = x_low:0.01:x_up;

// - The function which computes the initial guess, unused here
function [zu,dmval] = guess2(x,gam),
   cons = gam*x*(1-x^2/2)
   dcons = gam*(1-3*x^2/2)
   d2cons = -3*gam*x
   dmval = zeros(2,1)
   if x>xt then
     zu = [0 0 -cons -dcons]
     dmval(2) = -d2cons
   else
     zu = [2*x;2; -2*x+cons; -2*dcons]
     dmval(2) = d2cons
   end
endfunction

zu = bvode(xpoints,N,m,x_low,x_up,zeta,ipar,ltol,tol,fixpnt,...
           fsub2,dfsub2,gsub2,dgsub2,guess2);
scf(1); clf(); plot(xpoints,zu([1 3],:)) // the evolution of the solution phi and psi

// using an initial guess
ipar(9) = 1; // iguess

zu2 = bvode(xpoints,N,m,x_low,x_up,zeta,ipar,ltol,tol,fixpnt,...
            fsub2,dfsub2,gsub2,dgsub2,guess2);
scf(2); clf(); plot(xpoints,zu2([1 3],:)) // the evolution of the solution phi and psi
             ]]></programlisting>
            </listitem>
            <listitem>
                <para>
                    <emphasis role="bold">An eigenvalue problem:</emphasis>
                </para>
                <programlisting role="example"><![CDATA[
// y''(x)=-la*y(x)
// BV: y(0)=y'(0); y(1)=0
// Eigenfunctions and eigenvalues are y(x,n)=sin(s(n)*(1-x)), la(n)=s(n)^2,
// where s(n) are the zeros of f(s,n)=s+atan(s)-(n+1)*pi, n=0,1,2,...
// To get a third boundary condition, we choose y(0)=1
// (With y(x) also c*y(x) is a solution for each constant c.)
// We solve the following ode system:
// y''=-la*y
// la'=0
// BV: y(0)=y'(0), y(0)=1; y(1)=0
// z=[y(x) ; y'(x) ; la]

function rhs = fsub(x,z)
  rhs = [-z(3)*z(1);0]
endfunction

function g = gsub(i,z)
  g = [z(1)-z(2) z(1)-1 z(1)]
  g = g(i)
endfunction

// The following start function is good for the first 8 eigenfunctions.
function [z,lhs] = ystart(x,z,la0)
  z = [1;0;la0]
  lhs = [0;0]
endfunction

[a, b, m, n] =(0, 1, [2;1], 2);
zeta = [a a b];
N = 101;
x = linspace(a,b,N)';

// We have s(n)-(n+1/2)*pi -> 0 for n to infinity.
la0 = evstr(x_dialog('n-th eigenvalue: n= ?','10'));
la0 = (%pi/2+la0*%pi)^2;

z = bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,la0));
// The same call without any display
z = bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,la0),iprint=1);
// The same with a lot of display
z = bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,la0),iprint=-1);

clf()
plot(x,[z(1,:)' z(2,:)'])
xtitle(['Startvalue =  '+string(la0);'Eigenvalue = '+string(z(3,1))],'x',' ')
legend(['y(x)';'y''(x)']);
             ]]></programlisting>
                <scilab:image localized="true">
                    function rhs=fsub(x,z)
                    rhs=[-z(3)*z(1);0]
                    endfunction

                    function g=gsub(i,z)
                    g=[z(1)-z(2) z(1)-1 z(1)]
                    g=g(i)
                    endfunction

                    function [z,lhs]=ystart(x,z,la0)
                    z=[1;0;la0]
                    lhs=[0;0]
                    endfunction

                    a=0;b=1;
                    m=[2;1];
                    n=2;
                    zeta=[a a b];
                    N=101;
                    x=linspace(a,b,N)';

                    la0=10;
                    la0=(%pi/2+la0*%pi)^2;

                    z=bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,la0),iprint=1);

                    plot(x,[z(1,:)' z(2,:)']);
                    xtitle(['Startvalue =  '+string(la0);'Eigenvalue = '+string(z(3,1))],'x',' ');
                    legend(['y(x)';'y''(x)']);
                </scilab:image>

            </listitem>
            <listitem>
                <para>
                    <emphasis role="bold">A boundary value problem with more than one solution.</emphasis>
                </para>
                <programlisting role="example"><![CDATA[
// DE: y''(x) = -exp(y(x))
// BV: y(0)=0; y(1)=0
// This boundary value problem has more than one solution.
// It is demonstrated how to find two of them with the help of
// some preinformation of the solutions y(x) to build the function ystart.
// z = [y(x);y'(x)]

[a, b, m, n] = (0, 1, 2, 1);
zeta = [a b];
N = 101;
tol = 1e-8*[1 1];
x = linspace(a,b,N);

function rhs = fsub(x,z)
  rhs = -exp(z(1))
endfunction

function g = gsub(i,z)
  g = [z(1) z(1)]
  g = g(i)
endfunction

function [z,lhs] = ystart(x,z,M)
  // z = [4*x*(1-x)*M ; 4*(1-2*x)*M]
  z = [M;0]
  //lhs = [-exp(4*x*(1-x)*M)]
  lhs = 0
endfunction

for M = [1 4]
   if M==1
      z = bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,M),tol=tol);
   else
      z1 = bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,M),tol=tol);
   end
end

// Integrating the ode yield e.g. the two solutions yex and yex1.

function y = f(c)
  y = c.*(1-tanh(sqrt(c)/4).^2)-2;
endfunction
c = fsolve(2,f);

function y = yex(x,c)
  y = log(c/2*(1-tanh(sqrt(c)*(1/4-x/2)).^2))
endfunction

function y = f1(c1), y=2*c1^2+tanh(1/4/c1)^2-1; endfunction
c1 = fsolve(0.1,f1);

function y = yex1(x,c1)
  y = log((1-tanh((2*x-1)/4/c1).^2)/2/c1/c1)
endfunction

disp('norm(yex(x)-z(1,:))= ', norm(z(1,:)-yex(x)))
disp('norm(yex1(x)-z1(1,:))= ', norm(z1(1,:)-yex1(x)))
clf();
subplot(2,1,1)
plot2d(x,z(1,:),style=[5])
xtitle('Two different solutions','x',' ')
subplot(2,1,2)
plot2d(x,z1(1,:),style=[5])
xtitle(' ','x',' ')
             ]]></programlisting>
                <scilab:image localized="true">
                    a=0;
                    b=1;
                    m=2;
                    n=1;
                    zeta=[a b];
                    N=101;
                    tol=1e-8*[1 1];
                    x=linspace(a,b,N);

                    function rhs=fsub(x,z)
                    rhs=-exp(z(1));
                    endfunction

                    function g=gsub(i,z)
                    g=[z(1) z(1)]
                    g=g(i)
                    endfunction

                    function [z,lhs]=ystart(x,z,M)
                    //z=[4*x*(1-x)*M ; 4*(1-2*x)*M]
                    z=[M;0]
                    //lhs=[-exp(4*x*(1-x)*M)]
                    lhs=0
                    endfunction

                    for M=[1 4]
                    if M==1
                    z=bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,M),tol=tol,iprint=1);
                    else
                    z1=bvodeS(x,m,n,a,b,fsub,gsub,zeta,ystart=list(ystart,M),tol=tol,iprint=1);
                    end
                    end

                    // Integrating the ode yield e.g. the two solutions yex and yex1.

                    function y=f(c)
                    y=c.*(1-tanh(sqrt(c)/4).^2)-2;
                    endfunction
                    c=fsolve(2,f);

                    function y=yex(x,c)
                    y=log(c/2*(1-tanh(sqrt(c)*(1/4-x/2)).^2))
                    endfunction

                    function y=f1(c1), y=2*c1^2+tanh(1/4/c1)^2-1;endfunction
                    c1=fsolve(0.1,f1);

                    function y=yex1(x,c1)
                    y=log((1-tanh((2*x-1)/4/c1).^2)/2/c1/c1)
                    endfunction

                    subplot(2,1,1)
                    plot2d(x,z(1,:),style=[5])
                    xtitle('Two different solutions','x',' ')
                    subplot(2,1,2)
                    plot2d(x,z1(1,:),style=[5])
                    xtitle(' ','x',' ')
                </scilab:image>
            </listitem>
            <listitem>
                <para>
                    <emphasis role="bold">A multi-point boundary value problem.</emphasis>
                </para>
                <programlisting role="example"><![CDATA[
// DE y'''(x)=1
// z = [y(x);y'(x);y''(x)]
// BV: y(-1)=2 y(1)=2
// Side condition: y(0)=1

a = -1; b = 1; c = 0;
// The side condition point c must be included in the array fixpnt.
n = 1;
m = 3;

function rhs = fsub(x,z)
  rhs = 1
endfunction

function g = gsub(i,z)
  g = [z(1)-2 z(1)-1 z(1)-2]
  g = g(i)
endfunction

N = 10;
zeta = [a c b];
x = linspace(a,b,N);

z = bvodeS(x,m,n,a,b,fsub,gsub,zeta,fixpnt=c);

function y = yex(x)
    y = x.^3/6 + x.^2 - x/6 + 1
endfunction

disp(norm(yex(x)-z(1,:)),'norm(yex(x)-z(1,:))= ')
             ]]></programlisting>
            </listitem>
            <listitem>
                <para>
                    <emphasis role="bold">
                        Quantum Neumann equation, with 2 "eigenvalues" (c_1 and c2). Continuation being used.
                    </emphasis>
                </para>
                <programlisting role="example"><![CDATA[
// Quantum Neumann equation, with 2 "eigenvalues" c_1 and c_2
// (c_1=v-c_2-c_3, v is a parameter, used in continuation)
//
// diff(f,x,2) + (1/2)*(1/x + 1/(x-1) + 1/(x-y))*diff(f,x)
//      - (c_1/x + c_2/(x-1) + c_3/(x-y))* f(x) = 0
// diff(c_2,x)=0,  diff(c_3,x) = 0
//
// and 4 "boundary" conditions: diff(f,x)(a_k)=2*c_k*f(a_k) for
// k=1,2,3, a_k=(0, 1 , y)  and normalization f(1) = 1
//
// The z-vector is z_1=f, z_2=diff(f,x), z_3=c_2 and z_4=c_3
// The guess is chosen to have one node in [0,1],  f(x)=2*x-1
// such that f(1)=1, c_2 and c_3 are chosen to cancel poles in
// the differential equation at 1.0 and y, z_3=1, z_4=1/(2*y-1)
// Ref: http://arxiv.org/pdf/hep-th/0407005

y = 1.9d0;
eigens = zeros(3,40); // To store the results

// General setup for bvode

// Number of differential equations
ncomp = 3;

// Orders of equations
m = [2, 1, 1];

// Non-linear problem
ipar(1) = 1;

// Number of collocation points
ipar(2) = 3;

// Initial uniform mesh of 4 subintervals
ipar(3) = 4;
ipar(8) = 0;

// Size of fspace, ispace, see colnew.f to choose size
ipar(5) =  30000;
ipar(6) =  2000;

// Medium output
ipar(7) = 0;

// Initial approx is provided
ipar(9) = 1;

// fixpnt is an array containing all fixed points in the mesh, in
// particular "boundary" points, except aleft and aright, ipar[11] its
// size, here only one interior "boundary point"
ipar(11) = 1;
fixpnt = [1.0d0];

// Tolerances on all components z_1, z_2, z_3, z_4
ipar(4) = 4;

// Tolerance check on f and diff(f,x) and on c_2 and c_3
ltol = [1, 2, 3, 4];
tol = [1d-5, 1d-5, 1d-5, 1d-5];

// Define the differential equations

function [f]=fsub(x,z)
    f = [ -.5*(1/x+1/(x-1)+1/(x-y))*z(2) +...
     z(1) * ((v-z(3)-z(4))/x + z(3)/(x-1) + z(4)/(x-y)),...
    0,0];
endfunction
function [df] = dfsub(x,z)
    df = [(v-z(3)-z(4))/x + z(3)/(x-1) + z(4)/(x-y),...
    -.5*(1/x+1/(x-1)+1/(x-y)),z(1)/(x*(x-1)),z(1)*y/(x*(x-y));...
    0,0,0,0;0,0,0,0];
endfunction

// Boundary conditions

function [g]=gsub(i,z)
    select i
    case 1, g = z(2) - 2*z(1)*(v-z(3)-z(4))
    case 2, g = z(2) - 2*z(1)*z(3)
    case 3, g = z(1)-1.
    case 4, g = z(2) - 2*z(1)*z(4)
    end
endfunction
function [dg]=dgsub(i,z)
        select i
        case 1, dg = [-2*(v-z(3)-z(4)),1.,2*z(1),2*z(1)]
        case 2, dg = [-2*z(3),1.,-2*z(1),0]
        case 3, dg = [1,0,0,0]
        case 4, dg = [-2*z(4),1.,0,-2*z(1)]
        end
endfunction

// Start computation

// Locations of side conditions, sorted
zeta = [0.0d0, 1.0d0, 1.0d0, y];
// Interval ends
aleft = 0.0d0;
aright = y;

// Array of 40 values of v explored by continuation, and array of 202
// points where to evaluate function f.
valv = [linspace(0,.9,10) logspace(0,2,30)];
res = [linspace(0,.99,100) linspace(1,y,101)];

// eigenstates are characterized by number of nodes in [0,1] and in
// [1,y], here guess selects one node (zero) in [0,1] with linear
// f(x)=2*x-1 and constant c_2, c_3, so dmval=0. Notice that the z-vector
// has mstar = 4 components, while dmval has ncomp = 3 components.

function [z,dmval] = guess(x)
     z = [2*x-1, 2., 1., 1/(2*y-1)]
     dmval = [0,0,0]
endfunction

// First execution has ipar(9)=1 and uses the guess
// Subsequent executions have ipar(9)=3 and use continuation. This is
// run in tight closed loop to not disturb the stack

for i = 1:40
    v = valv(i);
    sol = bvode(res,ncomp,m,aleft,aright,zeta,ipar,ltol,tol,fixpnt,...
                fsub,dfsub,gsub,dgsub,guess);
    eigens(:,i) = [v;sol(3,101);sol(4,101)];  // c_2 and c_3 are constant!
    ipar(9) = 3;
end

// To see the evolution of the eigenvalues with v, disp(eigens)
// Note they evolve smoothly.
// To see the solution f for v=40, disp(sol(1,:)). Note that it vanishes
// exactly once in [0,1] at x close to 0.98, and becomes very small
// when x -> 0 and very large when x -> y.
// This is markedly different from the case  at small v.
// The continuation procedure allows to explore these exponential behaviours
// without skipping to other eigenstates.
             ]]></programlisting>
            </listitem>
        </itemizedlist>
    </refsection>
    <refsection>
        <title>Used Functions</title>
        <para>This function is based on the Fortran routine
            <literal>colnew</literal> developed by
        </para>
        <para>U. Ascher, Department of Computer Science, University of British
            Columbia, Vancouver, B.C. V6T 1W5, Canada
        </para>
        <para>G. Bader, institut f. Angewandte mathematik university of
            Heidelberg; im Neuenheimer feld 294d-6900 Heidelberg 1
        </para>
    </refsection>
    <refsection>
        <title>Bibliography</title>
        <orderedlist>
            <listitem>
                <para>U. Ascher, J. Christiansen and R.D. Russell, collocation
                    software for boundary-value ODEs, acm trans. math software 7 (1981),
                    209-222. this paper contains EXAMPLES where use of the code is
                    demonstrated.
                </para>
            </listitem>
            <listitem>
                <para>G. Bader and U. Ascher, a new basis implementation for a mixed
                    order boundary value ode solver, siam j. scient. stat. comput.
                    (1987).
                </para>
            </listitem>
            <listitem>
                <para>U. Ascher, J. Christiansen and R.D. Russell, a collocation
                    solver for mixed order systems of boundary value problems, math. comp.
                    33 (1979), 659-679.
                </para>
            </listitem>
            <listitem>
                <para>U. Ascher, J. Christiansen and R.D. russell, colsys - a
                    collocation code for boundary value problems, lecture notes comp.sc.
                    76, springer verlag, b. children et. al. (eds.) (1979), 164-185.
                </para>
            </listitem>
            <listitem>
                <para>C. Deboor and R. Weiss, solveblok: a package for solving almost
                    block diagonal linear systems, acm trans. math. software 6 (1980),
                    80-87.
                </para>
            </listitem>
        </orderedlist>
    </refsection>
    <refsection role="see also">
        <title>See also</title>
        <simplelist type="inline">
            <member>
                <link linkend="link">link</link>
            </member>
            <member>
                <link linkend="external">external</link>
            </member>
            <member>
                <link linkend="ode">ode</link>
            </member>
            <member>
                <link linkend="dae">dae</link>
            </member>
        </simplelist>
    </refsection>
</refentry>
