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<a name="Random-number-generator-initialization"></a>
Next: <a rel="next" accesskey="n" href="Sampling-from-a-random-number-generator.html">Sampling from a random number generator</a>,
Previous: <a rel="previous" accesskey="p" href="The-Random-Number-Generator-Interface.html">The Random Number Generator Interface</a>,
Up: <a rel="up" accesskey="u" href="Random-Number-Generation.html">Random Number Generation</a>
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<h3 class="section">17.3 Random number generator initialization</h3>
<div class="defun">
— Function: gsl_rng * <b>gsl_rng_alloc</b> (<var>const gsl_rng_type * T</var>)<var><a name="index-gsl_005frng_005falloc-1478"></a></var><br>
<blockquote><p>This function returns a pointer to a newly-created
instance of a random number generator of type <var>T</var>.
For example, the following code creates an instance of the Tausworthe
generator,
<pre class="example"> gsl_rng * r = gsl_rng_alloc (gsl_rng_taus);
</pre>
<p>If there is insufficient memory to create the generator then the
function returns a null pointer and the error handler is invoked with an
error code of <code>GSL_ENOMEM</code>.
<p>The generator is automatically initialized with the default seed,
<code>gsl_rng_default_seed</code>. This is zero by default but can be changed
either directly or by using the environment variable <code>GSL_RNG_SEED</code>
(see <a href="Random-number-environment-variables.html">Random number environment variables</a>).
<p>The details of the available generator types are
described later in this chapter.
</p></blockquote></div>
<div class="defun">
— Function: void <b>gsl_rng_set</b> (<var>const gsl_rng * r, unsigned long int s</var>)<var><a name="index-gsl_005frng_005fset-1479"></a></var><br>
<blockquote><p>This function initializes (or `seeds') the random number generator. If
the generator is seeded with the same value of <var>s</var> on two different
runs, the same stream of random numbers will be generated by successive
calls to the routines below. If different values of <var>s</var> are
supplied, then the generated streams of random numbers should be
completely different. If the seed <var>s</var> is zero then the standard seed
from the original implementation is used instead. For example, the
original Fortran source code for the <code>ranlux</code> generator used a seed
of 314159265, and so choosing <var>s</var> equal to zero reproduces this when
using <code>gsl_rng_ranlux</code>.
</p></blockquote></div>
<div class="defun">
— Function: void <b>gsl_rng_free</b> (<var>gsl_rng * r</var>)<var><a name="index-gsl_005frng_005ffree-1480"></a></var><br>
<blockquote><p>This function frees all the memory associated with the generator
<var>r</var>.
</p></blockquote></div>
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