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159 lines
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159 lines
8.3 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual describes how to install and use the GNU multiple precision
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arithmetic library, version 6.1.0.
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Copyright 1991, 1993-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.3 or any later
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version published by the Free Software Foundation; with no Invariant Sections,
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with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
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Texts being "You have freedom to copy and modify this GNU Manual, like GNU
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software". A copy of the license is included in
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GNU Free Documentation License. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Random State Initialization (GNU MP 6.1.0)</title>
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<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
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<meta name="keywords" content="Random State Initialization (GNU MP 6.1.0)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="Random-Number-Functions.html#Random-Number-Functions" rel="up" title="Random Number Functions">
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<link href="Random-State-Seeding.html#Random-State-Seeding" rel="next" title="Random State Seeding">
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<link href="Random-Number-Functions.html#Random-Number-Functions" rel="prev" title="Random Number Functions">
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</head>
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<body lang="en">
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<a name="Random-State-Initialization"></a>
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<div class="header">
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<p>
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Next: <a href="Random-State-Seeding.html#Random-State-Seeding" accesskey="n" rel="next">Random State Seeding</a>, Previous: <a href="Random-Number-Functions.html#Random-Number-Functions" accesskey="p" rel="prev">Random Number Functions</a>, Up: <a href="Random-Number-Functions.html#Random-Number-Functions" accesskey="u" rel="up">Random Number Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Random-State-Initialization-1"></a>
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<h3 class="section">9.1 Random State Initialization</h3>
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<a name="index-Random-number-state"></a>
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<a name="index-Initialization-functions-5"></a>
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<dl>
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<dt><a name="index-gmp_005frandinit_005fdefault"></a>Function: <em>void</em> <strong>gmp_randinit_default</strong> <em>(gmp_randstate_t <var>state</var>)</em></dt>
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<dd><p>Initialize <var>state</var> with a default algorithm. This will be a compromise
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between speed and randomness, and is recommended for applications with no
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special requirements. Currently this is <code>gmp_randinit_mt</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005frandinit_005fmt"></a>Function: <em>void</em> <strong>gmp_randinit_mt</strong> <em>(gmp_randstate_t <var>state</var>)</em></dt>
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<dd><a name="index-Mersenne-twister-random-numbers"></a>
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<p>Initialize <var>state</var> for a Mersenne Twister algorithm. This algorithm is
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fast and has good randomness properties.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005frandinit_005flc_005f2exp"></a>Function: <em>void</em> <strong>gmp_randinit_lc_2exp</strong> <em>(gmp_randstate_t <var>state</var>, const mpz_t <var>a</var>, unsigned long <var>c</var><!-- /@w -->, <span class="nolinebreak">mp_bitcnt_t</span> <var>m2exp</var><!-- /@w -->)</em></dt>
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<dd><a name="index-Linear-congruential-random-numbers"></a>
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<p>Initialize <var>state</var> with a linear congruential algorithm <em>X = (<var>a</var>*X + <var>c</var>) mod 2^<var>m2exp</var></em>.
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</p>
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<p>The low bits of <em>X</em> in this algorithm are not very random. The least
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significant bit will have a period no more than 2, and the second bit no more
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than 4, etc. For this reason only the high half of each <em>X</em> is actually
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used.
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</p>
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<p>When a random number of more than <em><var>m2exp</var>/2</em> bits is to be
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generated, multiple iterations of the recurrence are used and the results
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concatenated.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005frandinit_005flc_005f2exp_005fsize"></a>Function: <em>int</em> <strong>gmp_randinit_lc_2exp_size</strong> <em>(gmp_randstate_t <var>state</var>, mp_bitcnt_t <var>size</var>)</em></dt>
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<dd><a name="index-Linear-congruential-random-numbers-1"></a>
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<p>Initialize <var>state</var> for a linear congruential algorithm as per
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<code>gmp_randinit_lc_2exp</code>. <var>a</var>, <var>c</var> and <var>m2exp</var> are selected
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from a table, chosen so that <var>size</var> bits (or more) of each <em>X</em> will
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be used, i.e. <em><var>m2exp</var>/2 >= <var>size</var></em>.
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</p>
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<p>If successful the return value is non-zero. If <var>size</var> is bigger than the
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table data provides then the return value is zero. The maximum <var>size</var>
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currently supported is 128.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005frandinit_005fset"></a>Function: <em>void</em> <strong>gmp_randinit_set</strong> <em>(gmp_randstate_t <var>rop</var>, gmp_randstate_t <var>op</var>)</em></dt>
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<dd><p>Initialize <var>rop</var> with a copy of the algorithm and state from <var>op</var>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005frandinit"></a>Function: <em>void</em> <strong>gmp_randinit</strong> <em>(gmp_randstate_t <var>state</var>, <span class="nolinebreak">gmp_randalg_t</span> <var>alg</var><!-- /@w -->, …)</em></dt>
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<dd><p><strong>This function is obsolete.</strong>
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</p>
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<a name="index-GMP_005fRAND_005fALG_005fLC"></a>
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<a name="index-GMP_005fRAND_005fALG_005fDEFAULT"></a>
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<p>Initialize <var>state</var> with an algorithm selected by <var>alg</var>. The only
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choice is <code>GMP_RAND_ALG_LC</code>, which is <code>gmp_randinit_lc_2exp_size</code>
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described above. A third parameter of type <code>unsigned long</code> is required,
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this is the <var>size</var> for that function. <code>GMP_RAND_ALG_DEFAULT</code> or 0
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are the same as <code>GMP_RAND_ALG_LC</code>.
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</p>
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<a name="index-gmp_005ferrno"></a>
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<a name="index-GMP_005fERROR_005fUNSUPPORTED_005fARGUMENT"></a>
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<a name="index-GMP_005fERROR_005fINVALID_005fARGUMENT"></a>
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<p><code>gmp_randinit</code> sets bits in the global variable <code>gmp_errno</code> to
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indicate an error. <code>GMP_ERROR_UNSUPPORTED_ARGUMENT</code> if <var>alg</var> is
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unsupported, or <code>GMP_ERROR_INVALID_ARGUMENT</code> if the <var>size</var> parameter
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is too big. It may be noted this error reporting is not thread safe (a good
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reason to use <code>gmp_randinit_lc_2exp_size</code> instead).
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005frandclear"></a>Function: <em>void</em> <strong>gmp_randclear</strong> <em>(gmp_randstate_t <var>state</var>)</em></dt>
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<dd><p>Free all memory occupied by <var>state</var>.
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</p></dd></dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Random-State-Seeding.html#Random-State-Seeding" accesskey="n" rel="next">Random State Seeding</a>, Previous: <a href="Random-Number-Functions.html#Random-Number-Functions" accesskey="p" rel="prev">Random Number Functions</a>, Up: <a href="Random-Number-Functions.html#Random-Number-Functions" accesskey="u" rel="up">Random Number Functions</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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