109 lines
3.2 KiB
C
109 lines
3.2 KiB
C
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/* mpz_nextprime(p,t) - compute the next prime > t and store that in p.
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Copyright 1999, 2000, 2001 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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void
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mpz_nextprime (mpz_ptr p, mpz_srcptr t)
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{
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mpz_add_ui (p, t, 1L);
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while (! mpz_probab_prime_p (p, 5))
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mpz_add_ui (p, p, 1L);
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}
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#if 0
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/* This code is not yet tested. Will be enabled some time. */
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status unsigned short primes[] =
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{
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3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
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101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,
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191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,
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281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,
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389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,
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491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,
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607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,
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719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,
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829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,
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953,967,971,977,983,991,997
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};
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#define NUMBER_OF_PRIMES 167
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void
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mpz_nextprime (mpz_ptr p, mpz_srcptr n)
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{
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mpz_t tmp;
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unsigned short *moduli;
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unsigned long difference;
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int i;
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int composite;
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/* First handle tiny numbers */
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if (mpz_cmp_ui (n, 2) < 0)
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{
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mpz_set_ui (p, 2);
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return;
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}
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mpz_add_ui (p, n, 1);
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mpz_setbit (p, 0);
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if (mpz_cmp_ui (p, 7) <= 0)
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return;
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prime_limit = NUMBER_OF_PRIMES - 1;
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if (mpz_cmp_ui (p, primes[prime_limit]) <= 0)
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/* Just use first three entries (3,5,7) of table for small numbers */
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prime_limit = 3;
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if (prime_limit)
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{
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/* Compute residues modulo small odd primes */
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moduli = (unsigned short *) TMP_ALLOC (prime_limit * sizeof moduli[0]);
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for (i = 0; i < prime_limit; i++)
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moduli[i] = mpz_fdiv_ui (p, primes[i]);
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}
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for (difference = 0; ; difference += 2)
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{
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composite = 0;
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/* First check residues */
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for (i = 0; i < prime_limit; i++)
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{
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int acc, pr;
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composite |= (moduli[i] == 0);
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acc = moduli[i] + 2;
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pr = primes[i];
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moduli[i] = acc >= pr ? acc - pr : acc;
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}
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if (composite)
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continue;
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mpz_add_ui (p, p, difference);
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difference = 0;
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/* Miller-Rabin test */
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if (mpz_millerrabin (p, 2))
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break;
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}
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}
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#endif
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