<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >gmp_prob_prime</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="PHP 手册" HREF="index.html"><LINK REL="UP" TITLE="GMP Functions" HREF="ref.gmp.html"><LINK REL="PREVIOUS" TITLE="gmp_powm" HREF="function.gmp-powm.html"><LINK REL="NEXT" TITLE="gmp_random" HREF="function.gmp-random.html"><META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=UTF-8"></HEAD ><BODY CLASS="refentry" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >PHP 手册</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="function.gmp-powm.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="function.gmp-random.html" ACCESSKEY="N" >下一页</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="function.gmp-prob-prime" ></A >gmp_prob_prime</H1 ><DIV CLASS="refnamediv" ><A NAME="AEN64883" ></A ><P > (PHP 4 >= 4.0.4, PHP 5)</P >gmp_prob_prime -- Check if number is "probably prime"</DIV ><DIV CLASS="refsect1" ><A NAME="AEN64886" ></A ><H2 >Description</H2 >int <B CLASS="methodname" >gmp_prob_prime</B > ( resource a [, int reps] )<BR ></BR ><P > If this function returns 0, <CODE CLASS="parameter" >a</CODE > is definitely not prime. If it returns 1, then <CODE CLASS="parameter" >a</CODE > is "probably" prime. If it returns 2, then <CODE CLASS="parameter" >a</CODE > is surely prime. Reasonable values of <CODE CLASS="parameter" >reps</CODE > 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 > The function uses Miller-Rabin's probabilistic test. </P ><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" CLASS="EXAMPLE" ><TR ><TD ><DIV CLASS="example" ><A NAME="AEN64903" ></A ><P ><B >例 1. <B CLASS="function" >gmp_prob_prime()</B > example</B ></P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" CELLPADDING="5" ><TR ><TD ><code><font color="#000000"> <font color="#0000BB"><?php<br /></font><font color="#FF8000">// definitely not a prime<br /></font><font color="#007700">echo </font><font color="#0000BB">gmp_prob_prime</font><font color="#007700">(</font><font color="#DD0000">"6"</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /><br /></font><font color="#FF8000">// probably a prime<br /></font><font color="#007700">echo </font><font color="#0000BB">gmp_prob_prime</font><font color="#007700">(</font><font color="#DD0000">"1111111111111111111"</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /><br /></font><font color="#FF8000">// definitely a prime<br /></font><font color="#007700">echo </font><font color="#0000BB">gmp_prob_prime</font><font color="#007700">(</font><font color="#DD0000">"11"</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /></font><font color="#0000BB">?></font> </font> </code></TD ></TR ></TABLE ><P > The printout of the above program will be: </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" CELLPADDING="5" ><TR ><TD ><PRE CLASS="screen" >0 1 2</PRE ></TD ></TR ></TABLE ></DIV ></TD ></TR ></TABLE ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="function.gmp-powm.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >起始页</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="function.gmp-random.html" ACCESSKEY="N" >下一页</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >gmp_powm</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ref.gmp.html" ACCESSKEY="U" >上一级</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >gmp_random</TD ></TR ></TABLE ></DIV ></BODY ></HTML >