gmp_prob_prime

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_prob_primeCheck if number is "probably prime"

Açıklama

gmp_prob_prime(GMP|int|string $num, int $repetitions = 10): int

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

Değiştirgeler

num

The number being checked as a prime.

Bir GMP nesnesi, bir tamsayı veya sayısal bir dizge.

repetitions

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

Bir GMP nesnesi, bir tamsayı veya sayısal bir dizge.

Dönen Değerler

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

Örnekler

Örnek 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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User Contributed Notes 1 note

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florin dot ciuica at yahoo dot com
7 years ago
<?php
    $max
= 2147483647;
   
   
$primesFound = 0;
   
$probablePrimes = 0;

    for (
$x = 1; $x <= $max; $x++) {
       
$primeStatus = gmp_prob_prime($x);
        if (
$primeStatus == 1) {
           
$probablePrimes++;
        } else if (
$primeStatus == 2) {
           
$primesFound++;
        }
    }
    echo
"Total primes found: " . $primesFound . " between 1 and " . $max . ". Probable primes in this interval: " . $probablePrimes;
?>

Based on that the following results were obtained:

1 - 100000      - certain primes found: 9592,     probable: 0
1 - 1000000     - certain primes found: 78498,    probable: 0
1 - 10000000    - certain primes found: 78498,    probable: 586081
1 - 100000000   - certain primes found: 78498,    probable: 5682957
1 - 1000000000  - certain primes found: 78498,    probable: 50769036
1 - 2147483647  - certain primes found: 78498,    probable: 105019067
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