Mersenne primes: Difference between revisions

{{libheader|GMP}}

Alternatively, we can use GMP to find the first 23 Mersenne primes in about the same time as the corresponding Wren entry.

<syntaxhighlight lang="c">#include <stdio.h>

#include <stdbool.h>

#include <stdint.h>

#include <gmp.h>

#define MAX 23

bool isPrime(uint64_t n) {

uint64_t test;

if (n < 2) return false;

if (n % 2 == 0) return n == 2;

if (n % 3 == 0) return n == 3;

test = 5;

while (test * test < n) {

if (n % test == 0) return false;

test += 2;

if (n % test == 0) return false;

test += 4;

}

return true;

}

int main() {

uint64_t p = 2;

int count = 0;

mpz_t m, one;

mpz_init(m);

mpz_init_set_ui(one, 1);

while (true) {

mpz_mul_2exp(m, one, p);

mpz_sub_ui(m, m, 1);

if (mpz_probab_prime_p(m, 15) > 0) {

printf("2 ^ %ld - 1\n", p);

if (++count == MAX) break;

}

while (true) {

p = (p > 2) ? p + 2 : 3;

if (isPrime(p)) break;

}

}

mpz_clear(m);

mpz_clear(one);

return 0;

} </syntaxhighlight>

{{out}}

<pre>

Same as Wren example.

</pre>