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 Last updated: Sat, 07 Jan 2012

# gmp_prob_prime

(PHP 4 >= 4.0.4, PHP 5)

gmp_prob_primeCheck if number is "probably prime"

### 설명

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.

### 인수

a

The number being checked as a prime.

GMP 수 resource나 수로 변환할 수 있는 문자열일 수 있습니다.

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.

GMP 수 resource나 수로 변환할 수 있는 문자열일 수 있습니다.

### 반환값

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.

### 예제

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";?> ```

위 예제의 출력:

```0
1
2
```

User Contributed Notes gmp_prob_prime - [1 notes]
-1
roland at mxchange dot org
2 years ago
``` Here is a simple demonstration code to fine prime possibilities. On my 64 bit Linux box I can only go until 61, larger numbers causes warnings due to the EXP number: <?php for (\$idx = 0; \$idx <= 61; \$idx++) {     \$pow =  (gmp_strval(gmp_pow('2', \$idx)) - 1);     \$prop = gmp_prob_prime(\$pow);     if (\$prop > 0) {         echo 'idx=' . \$idx . "\n--------\n";         echo 'pow=' . \$pow . "\n";         echo 'prop=' . \$prop . "\n------\n";     } } ?> By 'pow' is the possible prime number. ```