gmp_prob_prime Check if number is "probably prime"


gmp_prob_prime

(PHP 4 >= 4.0.4, PHP 5)

gmp_prob_primeCheck if number is "probably prime"

说明

int gmp_prob_prime ( resource $a [, int $reps = 10 ] )

The function uses Miller-Rabin's probabilistic test to check if a number is a prime.

参数

a

The number being checked as a prime.

可以是一个 GMP 数据 resouce,或一个可以转换为数值的字符串。

reps

Reasonable values of reps vary from 5 to 10 (default being 10); a higher value lowers the probability for a non-prime to pass as a "probable" prime.

可以是一个 GMP 数据 resouce,或一个可以转换为数值的字符串。

返回值

If this function returns 0, a is definitely not prime. If it returns 1, then a is "probably" prime. If it returns 2, then a is surely prime.

范例

Example #1 gmp_prob_prime() example

<?php
// definitely not a prime
echo gmp_prob_prime("6") . " ";

// probably a prime
echo gmp_prob_prime("1111111111111111111") . " ";

// definitely a prime
echo gmp_prob_prime("11") . " ";
?>

以上例程会输出:

0
1
2


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