gmp_prob_prime
(PHP 4 >= 4.0.4, PHP 5)
gmp_prob_prime -- Check if number is "probably prime"
Description
int
gmp_prob_prime
( resource a [, int reps] )
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. 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.
The function uses Miller-Rabin's probabilistic test.
例子 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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The printout of the above program will be:
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