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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.4 $ -->
<!-- splitted from ./en/functions/gmp.xml, last change in rev 1.1 -->
<refentry id="function.gmp-prob-prime">
<refnamediv>
<refname>gmp_prob_prime</refname>
<refpurpose>Check if number is "probably prime"</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>int</type><methodname>gmp_prob_prime</methodname>
<methodparam><type>resource</type><parameter>a</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>reps</parameter></methodparam>
</methodsynopsis>
<para>
If this function returns 0, <parameter>a</parameter> is
definitely not prime. If it returns 1, then
<parameter>a</parameter> is "probably" prime. If it returns 2,
then <parameter>a</parameter> is surely prime. Reasonable values
of <parameter>reps</parameter> vary from 5 to 10 (default being
10); a higher value lowers the probability for a non-prime to
pass as a "probable" prime.
</para>
<para>
The function uses Miller-Rabin's probabilistic test.
</para>
<example>
<title><function>gmp_prob_prime</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
// definitely not a prime
echo gmp_prob_prime("6") . "\n";
// probably a prime
echo gmp_prob_prime("1111111111111111111") . "\n";
// definitely a prime
echo gmp_prob_prime("11") . "\n";
?>
]]>
</programlisting>
<para>
The printout of the above program will be:
</para>
<screen>
<![CDATA[
0
1
2
]]>
</screen>
</example>
</refsect1>
</refentry>
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