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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Check if number is "probably prime"</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.gmp-powm.html">gmp_powm</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.gmp-random.html">gmp_random</a></div> <div class="up"><a href="ref.gmp.html">GMP Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="function.gmp-prob-prime" class="refentry"> <div class="refnamediv"> <h1 class="refname">gmp_prob_prime</h1> <p class="verinfo">(PHP 4 >= 4.0.4, PHP 5)</p><p class="refpurpose"><span class="refname">gmp_prob_prime</span> — <span class="dc-title">Check if number is "probably prime"</span></p> </div> <div class="refsect1 description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">int</span> <span class="methodname"><b><b>gmp_prob_prime</b></b></span> ( <span class="methodparam"><span class="type">resource</span> <tt class="parameter">$a</tt></span> [, <span class="methodparam"><span class="type">int</span> <tt class="parameter">$reps</tt></span> ] )</div> <p class="para rdfs-comment"> The function uses Miller-Rabin's probabilistic test to check if a number is a prime. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">a</tt></i></span> <dd> <p class="para"> The number being checked as a prime. </p> <p class="para">It can be either a GMP number <a href="language.types.resource.html" class="type resource">resource</a>, or a numeric string given that it is possible to convert the latter to a number.</p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">reps</tt></i></span> <dd> <p class="para"> Reasonable values of <i><tt class="parameter">reps</tt></i> vary from 5 to 10 (default being 10); a higher value lowers the probability for a non-prime to pass as a "probable" prime. </p> <p class="para">It can be either a GMP number <a href="language.types.resource.html" class="type resource">resource</a>, or a numeric string given that it is possible to convert the latter to a number.</p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> If this function returns 0, <i><tt class="parameter">a</tt></i> is definitely not prime. If it returns 1, then <i><tt class="parameter">a</tt></i> is "probably" prime. If it returns 2, then <i><tt class="parameter">a</tt></i> is surely prime. </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 <b>gmp_prob_prime()</b> example</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// definitely not a prime<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">gmp_prob_prime</span><span style="color: #007700">(</span><span style="color: #DD0000">"6"</span><span style="color: #007700">) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// probably a prime<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">gmp_prob_prime</span><span style="color: #007700">(</span><span style="color: #DD0000">"1111111111111111111"</span><span style="color: #007700">) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// definitely a prime<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">gmp_prob_prime</span><span style="color: #007700">(</span><span style="color: #DD0000">"11"</span><span style="color: #007700">) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents"><pre><div class="cdata"><pre>012</pre></div> </pre></div> </div> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.gmp-powm.html">gmp_powm</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.gmp-random.html">gmp_random</a></div> <div class="up"><a href="ref.gmp.html">GMP Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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