Php/docs/function.gmp-prob-prime

• PHP Manual
• GMP 函数
• Check if number is "probably prime"

gmp_prob_prime

(PHP 4 >= 4.0.4, PHP 5, PHP 7)

gmp_prob_prime — Check if number is "probably prime"

说明

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

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.

PHP 5.5 之前为 GMP 数值资源，PHP 5.6 之后为 GMP 对象或数字，或可以转为数字的字符串。

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.

PHP 5.5 之前为 GMP 数值资源，PHP 5.6 之后为 GMP 对象或数字，或可以转为数字的字符串。

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 primeecho gmp_prob_prime("6") . "\n";// probably a primeecho gmp_prob_prime("1111111111111111111") . "\n";// definitely a primeecho gmp_prob_prime("11") . "\n";?>

以上例程会输出：

0
1
2