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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@84537 c90b9560-bf6c-de11-be94-00142212c4b1
81 lines
3 KiB
XML
81 lines
3 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.4 $ -->
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<!-- splitted from ./en/functions/math.xml, last change in rev 1.2 -->
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<refentry id="function.mt-rand">
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<refnamediv>
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<refname>mt_rand</refname>
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<refpurpose>Generate a better random value</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<methodsynopsis>
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<type>int</type><methodname>mt_rand</methodname>
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<methodparam choice="opt"><type>int</type><parameter>min</parameter></methodparam>
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<methodparam><type>int</type><parameter>max</parameter></methodparam>
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</methodsynopsis>
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<simpara>
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Many random number generators of older libcs have dubious or
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unknown characteristics and are slow. By default, PHP uses the
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libc random number generator with the <function>rand</function>
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function. <function>mt_rand</function> function is a drop-in
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replacement for this. It uses a random number generator with
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known characteristics, the Mersenne Twister, which will produce
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random numbers that should be suitable for seeding some kinds
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of cryptography (see the home pages for details) and is four
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times faster than what the average libc provides. The Homepage
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of the Mersenne Twister can be found at
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<ulink url="&url.mersenne;">&url.mersenne;</ulink>, and an
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optimized version of the MT source is available from
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<ulink url="&url.mersenne.twister;">&url.mersenne.twister;
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</ulink>.
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</simpara>
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<simpara>
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If called without the optional <parameter>min</parameter>,
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<parameter>max</parameter> arguments <function>mt_rand</function>
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returns a pseudo-random value between 0 and
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<constant>RAND_MAX</constant>. If you want a random number
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between 5 and 15 (inclusive), for example, use <literal>mt_rand
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(5, 15)</literal>.
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</simpara>
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<simpara>
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In older versions of PHP, you had to seed the random number generator
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before use with <function>mt_srand</function>. Since 4.2.0 this is no
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longer necessary.
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</simpara>
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<note>
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<para>
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In versions before 3.0.7 the meaning of
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<parameter>max</parameter> was <parameter>range</parameter>. To
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get the same results in these versions the short example should
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be <literal>mt_rand (5, 11)</literal> to get a random number
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between 5 and 15.
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</para>
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</note>
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<simpara>
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See also <function>mt_srand</function>,
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<function>mt_getrandmax</function> and
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<function>rand</function>.
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</simpara>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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