Return to nextprime.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpz

Annotation of OpenXM_contrib/gmp/mpz/nextprime.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpz_nextprime(p,t) - compute the next prime > t and store that in p.
                      2:
                      3: Copyright (C) 1999, 2000 Free Software Foundation, Inc.
                      4:
                      5: This file is part of the GNU MP Library.
                      6:
                      7: The GNU MP Library is free software; you can redistribute it and/or modify
                      8: it under the terms of the GNU Lesser General Public License as published by
                      9: the Free Software Foundation; either version 2.1 of the License, or (at your
                     10: option) any later version.
                     11:
                     12: The GNU MP Library is distributed in the hope that it will be useful, but
                     13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
                     15: License for more details.
                     16:
                     17: You should have received a copy of the GNU Lesser General Public License
                     18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     20: MA 02111-1307, USA. */
                     21:
                     22: #include "gmp.h"
                     23: #include "gmp-impl.h"
                     24:
                     25: void
                     26: #if __STDC__
                     27: mpz_nextprime (mpz_ptr p, mpz_srcptr t)
                     28: #else
                     29: mpz_nextprime (p, t)
                     30:      mpz_ptr    p;
                     31:      mpz_srcptr t;
                     32: #endif
                     33: {
                     34:   mpz_add_ui (p, t, 1L);
                     35:   while (! mpz_probab_prime_p (p, 5))
                     36:     mpz_add_ui (p, p, 1L);
                     37: }
                     38:
                     39: #if 0
                     40: /* This code is not yet tested.  Will be enabled in 3.1. */
                     41:
                     42: status unsigned short primes[] =
                     43: {
                     44: 3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
                     45: 101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,
                     46: 191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,
                     47: 281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,
                     48: 389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,
                     49: 491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,
                     50: 607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,
                     51: 719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,
                     52: 829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,
                     53: 953,967,971,977,983,991,997
                     54: };
                     55:
                     56: #define NUMBER_OF_PRIMES 167
                     57:
                     58: void
                     59: #if __STDC__
                     60: mpz_nextprime (mpz_ptr p, mpz_srcptr n)
                     61: #else
                     62: mpz_nextprime (p, n)
                     63:      mpz_ptr p;
                     64:      mpz_srcptr n;
                     65: #endif
                     66: {
                     67:   mpz_t tmp;
                     68:   unsigned short *moduli;
                     69:   unsigned long difference;
                     70:   int i;
                     71:   int composite;
                     72:
                     73:   /* First handle tiny numbers */
                     74:   if (mpz_cmp_ui (n, 2) < 0)
                     75:     {
                     76:       mpz_set_ui (p, 2);
                     77:       return;
                     78:     }
                     79:   mpz_add_ui (p, n, 1);
                     80:   mpz_setbit (p, 0);
                     81:
                     82:   if (mpz_cmp_ui (p, 7) <= 0)
                     83:     return;
                     84:
                     85:   prime_limit = NUMBER_OF_PRIMES - 1;
                     86:   if (mpz_cmp_ui (p, primes[prime_limit]) <= 0)
                     87:     /* Just use first three entries (3,5,7) of table for small numbers */
                     88:     prime_limit = 3;
                     89:   if (prime_limit)
                     90:     {
                     91:       /* Compute residues modulo small odd primes */
                     92:       moduli = (unsigned short *) TMP_ALLOC (prime_limit * sizeof moduli[0]);
                     93:       for (i = 0; i < prime_limit; i++)
                     94:        moduli[i] = mpz_fdiv_ui (p, primes[i]);
                     95:     }
                     96:   for (difference = 0; ; difference += 2)
                     97:     {
                     98:       composite = 0;
                     99:
                    100:       /* First check residues */
                    101:       for (i = 0; i < prime_limit; i++)
                    102:        {
                    103:          int acc, pr;
                    104:          composite |= (moduli[i] == 0);
                    105:          acc = moduli[i] + 2;
                    106:          pr = primes[i];
                    107:          moduli[i] = acc >= pr ? acc - pr : acc;
                    108:        }
                    109:       if (composite)
                    110:        continue;
                    111:
                    112:       mpz_add_ui (p, p, difference);
                    113:       difference = 0;
                    114:
                    115:       /* Miller-Rabin test */
                    116:       if (mpz_millerrabin (p, 2))
                    117:        break;
                    118:     }
                    119: }
                    120: #endif