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<title>Auxiliary random number generator functions - GNU Scientific Library -- Reference Manual</title>
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<h3 class="section">17.5 Auxiliary random number generator functions</h3>
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<p>The following functions provide information about an existing
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generator. You should use them in preference to hard-coding the generator
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parameters into your own code.
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— Function: const char * <b>gsl_rng_name</b> (<var>const gsl_rng * r</var>)<var><a name="index-gsl_005frng_005fname-1380"></a></var><br>
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<blockquote><p>This function returns a pointer to the name of the generator.
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<pre class="example"> printf ("r is a '%s' generator\n",
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<p class="noindent">would print something like <code>r is a 'taus' generator</code>.
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</p></blockquote></div>
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— Function: unsigned long int <b>gsl_rng_max</b> (<var>const gsl_rng * r</var>)<var><a name="index-gsl_005frng_005fmax-1381"></a></var><br>
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<blockquote><p><code>gsl_rng_max</code> returns the largest value that <code>gsl_rng_get</code>
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</p></blockquote></div>
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— Function: unsigned long int <b>gsl_rng_min</b> (<var>const gsl_rng * r</var>)<var><a name="index-gsl_005frng_005fmin-1382"></a></var><br>
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<blockquote><p><code>gsl_rng_min</code> returns the smallest value that <code>gsl_rng_get</code>
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can return. Usually this value is zero. There are some generators with
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algorithms that cannot return zero, and for these generators the minimum
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</p></blockquote></div>
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— Function: void * <b>gsl_rng_state</b> (<var>const gsl_rng * r</var>)<var><a name="index-gsl_005frng_005fstate-1383"></a></var><br>
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— Function: size_t <b>gsl_rng_size</b> (<var>const gsl_rng * r</var>)<var><a name="index-gsl_005frng_005fsize-1384"></a></var><br>
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<blockquote><p>These functions return a pointer to the state of generator <var>r</var> and
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its size. You can use this information to access the state directly. For
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example, the following code will write the state of a generator to a
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<pre class="example"> void * state = gsl_rng_state (r);
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size_t n = gsl_rng_size (r);
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fwrite (state, n, 1, stream);
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— Function: const gsl_rng_type ** <b>gsl_rng_types_setup</b> (<var>void</var>)<var><a name="index-gsl_005frng_005ftypes_005fsetup-1385"></a></var><br>
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<blockquote><p>This function returns a pointer to an array of all the available
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generator types, terminated by a null pointer. The function should be
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called once at the start of the program, if needed. The following code
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fragment shows how to iterate over the array of generator types to print
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the names of the available algorithms,
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<pre class="example"> const gsl_rng_type **t, **t0;
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t0 = gsl_rng_types_setup ();
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printf ("Available generators:\n");
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for (t = t0; *t != 0; t++)
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printf ("%s\n", (*t)->name);
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