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<title>GNU Scientific Library &ndash; Reference Manual: Initializing the Multidimensional Minimizer</title>

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<a name="Initializing-the-Multidimensional-Minimizer"></a>
<div class="header">
<p>
Next: <a href="Providing-a-function-to-minimize.html#Providing-a-function-to-minimize" accesskey="n" rel="next">Providing a function to minimize</a>, Previous: <a href="Multimin-Caveats.html#Multimin-Caveats" accesskey="p" rel="previous">Multimin Caveats</a>, Up: <a href="Multidimensional-Minimization.html#Multidimensional-Minimization" accesskey="u" rel="up">Multidimensional Minimization</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Initializing-the-Multidimensional-Minimizer-1"></a>
<h3 class="section">37.3 Initializing the Multidimensional Minimizer</h3>
<p>The following function initializes a multidimensional minimizer.  The
minimizer itself depends only on the dimension of the problem and the
algorithm and can be reused for different problems.
</p>
<dl>
<dt><a name="index-gsl_005fmultimin_005ffdfminimizer_005falloc"></a>Function: <em>gsl_multimin_fdfminimizer *</em> <strong>gsl_multimin_fdfminimizer_alloc</strong> <em>(const gsl_multimin_fdfminimizer_type * <var>T</var>, size_t <var>n</var>)</em></dt>
<dt><a name="index-gsl_005fmultimin_005ffminimizer_005falloc"></a>Function: <em>gsl_multimin_fminimizer *</em> <strong>gsl_multimin_fminimizer_alloc</strong> <em>(const gsl_multimin_fminimizer_type * <var>T</var>, size_t <var>n</var>)</em></dt>
<dd><a name="index-gsl_005fmultimin_005ffdfminimizer"></a>
<a name="index-gsl_005fmultimin_005ffminimizer"></a>
<a name="index-gsl_005fmultimin_005ffdfminimizer_005ftype"></a>
<a name="index-gsl_005fmultimin_005ffminimizer_005ftype"></a>
<p>This function returns a pointer to a newly allocated instance of a
minimizer of type <var>T</var> for an <var>n</var>-dimension function.  If there
is insufficient memory to create the minimizer then the function returns
a null pointer and the error handler is invoked with an error code of
<code>GSL_ENOMEM</code>.
</p></dd></dl>

<dl>
<dt><a name="index-gsl_005fmultimin_005ffdfminimizer_005fset"></a>Function: <em>int</em> <strong>gsl_multimin_fdfminimizer_set</strong> <em>(gsl_multimin_fdfminimizer * <var>s</var>, gsl_multimin_function_fdf * <var>fdf</var>, const gsl_vector * <var>x</var>, double <var>step_size</var>, double <var>tol</var>)</em></dt>
<dt><a name="index-gsl_005fmultimin_005ffminimizer_005fset"></a>Function: <em>int</em> <strong>gsl_multimin_fminimizer_set</strong> <em>(gsl_multimin_fminimizer * <var>s</var>, gsl_multimin_function * <var>f</var>, const gsl_vector * <var>x</var>, const gsl_vector * <var>step_size</var>)</em></dt>
<dd><p>The function <code>gsl_multimin_fdfminimizer_set</code> initializes the minimizer <var>s</var> to minimize the function
<var>fdf</var> starting from the initial point <var>x</var>.  The size of the
first trial step is given by <var>step_size</var>.  The accuracy of the line
minimization is specified by <var>tol</var>.  The precise meaning of this
parameter depends on the method used.  Typically the line minimization
is considered successful if the gradient of the function <em>g</em> is
orthogonal to the current search direction <em>p</em> to a relative
accuracy of <var>tol</var>, where <em>dot(p,g) &lt; tol |p| |g|</em>.  A <var>tol</var> value of 0.1 is 
suitable for most purposes, since line minimization only needs to
be carried out approximately.    Note that setting <var>tol</var> to zero will
force the use of &ldquo;exact&rdquo; line-searches, which are extremely expensive.
</p>
<p>The function <code>gsl_multimin_fminimizer_set</code> initializes the minimizer <var>s</var> to minimize the function
<var>f</var>, starting from the initial point
<var>x</var>. The size of the initial trial steps is given in vector
<var>step_size</var>. The precise meaning of this parameter depends on the
method used. 
</p></dd></dl>

<dl>
<dt><a name="index-gsl_005fmultimin_005ffdfminimizer_005ffree"></a>Function: <em>void</em> <strong>gsl_multimin_fdfminimizer_free</strong> <em>(gsl_multimin_fdfminimizer * <var>s</var>)</em></dt>
<dt><a name="index-gsl_005fmultimin_005ffminimizer_005ffree"></a>Function: <em>void</em> <strong>gsl_multimin_fminimizer_free</strong> <em>(gsl_multimin_fminimizer * <var>s</var>)</em></dt>
<dd><p>This function frees all the memory associated with the minimizer
<var>s</var>.
</p></dd></dl>

<dl>
<dt><a name="index-gsl_005fmultimin_005ffdfminimizer_005fname"></a>Function: <em>const char *</em> <strong>gsl_multimin_fdfminimizer_name</strong> <em>(const gsl_multimin_fdfminimizer * <var>s</var>)</em></dt>
<dt><a name="index-gsl_005fmultimin_005ffminimizer_005fname"></a>Function: <em>const char *</em> <strong>gsl_multimin_fminimizer_name</strong> <em>(const gsl_multimin_fminimizer * <var>s</var>)</em></dt>
<dd><p>This function returns a pointer to the name of the minimizer.  For example,
</p>
<div class="example">
<pre class="example">printf (&quot;s is a '%s' minimizer\n&quot;, 
        gsl_multimin_fdfminimizer_name (s));
</pre></div>

<p>would print something like <code>s is a 'conjugate_pr' minimizer</code>.
</p></dd></dl>

<hr>
<div class="header">
<p>
Next: <a href="Providing-a-function-to-minimize.html#Providing-a-function-to-minimize" accesskey="n" rel="next">Providing a function to minimize</a>, Previous: <a href="Multimin-Caveats.html#Multimin-Caveats" accesskey="p" rel="previous">Multimin Caveats</a>, Up: <a href="Multidimensional-Minimization.html#Multidimensional-Minimization" accesskey="u" rel="up">Multidimensional Minimization</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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