gmp_prob_prime

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

gmp_prob_primeCheck if number is "probably prime"

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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.

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a

The number being checked as a prime.

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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.

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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.

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Example #1 gmp_prob_prime() example

<?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";
?>

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