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
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