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/* mpz_nextprime(p,t) - compute the next prime > t and store that in p.
Copyright (C) 1999, 2000 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
void
#if __STDC__
mpz_nextprime (mpz_ptr p, mpz_srcptr t)
#else
mpz_nextprime (p, t)
mpz_ptr p;
mpz_srcptr t;
#endif
{
mpz_add_ui (p, t, 1L);
while (! mpz_probab_prime_p (p, 5))
mpz_add_ui (p, p, 1L);
}
#if 0
/* This code is not yet tested. Will be enabled in 3.1. */
status unsigned short primes[] =
{
3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,
191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,
281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,
389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,
491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,
607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,
719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,
829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,
953,967,971,977,983,991,997
};
#define NUMBER_OF_PRIMES 167
void
#if __STDC__
mpz_nextprime (mpz_ptr p, mpz_srcptr n)
#else
mpz_nextprime (p, n)
mpz_ptr p;
mpz_srcptr n;
#endif
{
mpz_t tmp;
unsigned short *moduli;
unsigned long difference;
int i;
int composite;
/* First handle tiny numbers */
if (mpz_cmp_ui (n, 2) < 0)
{
mpz_set_ui (p, 2);
return;
}
mpz_add_ui (p, n, 1);
mpz_setbit (p, 0);
if (mpz_cmp_ui (p, 7) <= 0)
return;
prime_limit = NUMBER_OF_PRIMES - 1;
if (mpz_cmp_ui (p, primes[prime_limit]) <= 0)
/* Just use first three entries (3,5,7) of table for small numbers */
prime_limit = 3;
if (prime_limit)
{
/* Compute residues modulo small odd primes */
moduli = (unsigned short *) TMP_ALLOC (prime_limit * sizeof moduli[0]);
for (i = 0; i < prime_limit; i++)
moduli[i] = mpz_fdiv_ui (p, primes[i]);
}
for (difference = 0; ; difference += 2)
{
composite = 0;
/* First check residues */
for (i = 0; i < prime_limit; i++)
{
int acc, pr;
composite |= (moduli[i] == 0);
acc = moduli[i] + 2;
pr = primes[i];
moduli[i] = acc >= pr ? acc - pr : acc;
}
if (composite)
continue;
mpz_add_ui (p, p, difference);
difference = 0;
/* Miller-Rabin test */
if (mpz_millerrabin (p, 2))
break;
}
}
#endif
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