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Diffstat (limited to 'Build/source/libs/gmp/gmp-6.0.0/mpz/millerrabin.c')
-rw-r--r-- | Build/source/libs/gmp/gmp-6.0.0/mpz/millerrabin.c | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/Build/source/libs/gmp/gmp-6.0.0/mpz/millerrabin.c b/Build/source/libs/gmp/gmp-6.0.0/mpz/millerrabin.c new file mode 100644 index 00000000000..e1ce32c8937 --- /dev/null +++ b/Build/source/libs/gmp/gmp-6.0.0/mpz/millerrabin.c @@ -0,0 +1,124 @@ +/* mpz_millerrabin(n,reps) -- An implementation of the probabilistic primality + test found in Knuth's Seminumerical Algorithms book. If the function + mpz_millerrabin() returns 0 then n is not prime. If it returns 1, then n is + 'probably' prime. The probability of a false positive is (1/4)**reps, where + reps is the number of internal passes of the probabilistic algorithm. Knuth + indicates that 25 passes are reasonable. + + THE FUNCTIONS IN THIS FILE ARE FOR INTERNAL USE ONLY. THEY'RE ALMOST + CERTAIN TO BE SUBJECT TO INCOMPATIBLE CHANGES OR DISAPPEAR COMPLETELY IN + FUTURE GNU MP RELEASES. + +Copyright 1991, 1993, 1994, 1996-2002, 2005 Free Software Foundation, Inc. + +Contributed by John Amanatides. + +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 either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + +or + + * the GNU General Public License as published by the Free Software + Foundation; either version 2 of the License, or (at your option) any + later version. + +or both in parallel, as here. + +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 General Public License +for more details. + +You should have received copies of the GNU General Public License and the +GNU Lesser General Public License along with the GNU MP Library. If not, +see https://www.gnu.org/licenses/. */ + +#include "gmp.h" +#include "gmp-impl.h" + +static int millerrabin (mpz_srcptr, mpz_srcptr, + mpz_ptr, mpz_ptr, + mpz_srcptr, unsigned long int); + +int +mpz_millerrabin (mpz_srcptr n, int reps) +{ + int r; + mpz_t nm1, nm3, x, y, q; + unsigned long int k; + gmp_randstate_t rstate; + int is_prime; + TMP_DECL; + TMP_MARK; + + MPZ_TMP_INIT (nm1, SIZ (n) + 1); + mpz_sub_ui (nm1, n, 1L); + + MPZ_TMP_INIT (x, SIZ (n) + 1); + MPZ_TMP_INIT (y, 2 * SIZ (n)); /* mpz_powm_ui needs excessive memory!!! */ + + /* Perform a Fermat test. */ + mpz_set_ui (x, 210L); + mpz_powm (y, x, nm1, n); + if (mpz_cmp_ui (y, 1L) != 0) + { + TMP_FREE; + return 0; + } + + MPZ_TMP_INIT (q, SIZ (n)); + + /* Find q and k, where q is odd and n = 1 + 2**k * q. */ + k = mpz_scan1 (nm1, 0L); + mpz_tdiv_q_2exp (q, nm1, k); + + /* n-3 */ + MPZ_TMP_INIT (nm3, SIZ (n) + 1); + mpz_sub_ui (nm3, n, 3L); + ASSERT (mpz_cmp_ui (nm3, 1L) >= 0); + + gmp_randinit_default (rstate); + + is_prime = 1; + for (r = 0; r < reps && is_prime; r++) + { + /* 2 to n-2 inclusive, don't want 1, 0 or -1 */ + mpz_urandomm (x, rstate, nm3); + mpz_add_ui (x, x, 2L); + + is_prime = millerrabin (n, nm1, x, y, q, k); + } + + gmp_randclear (rstate); + + TMP_FREE; + return is_prime; +} + +static int +millerrabin (mpz_srcptr n, mpz_srcptr nm1, mpz_ptr x, mpz_ptr y, + mpz_srcptr q, unsigned long int k) +{ + unsigned long int i; + + mpz_powm (y, x, q, n); + + if (mpz_cmp_ui (y, 1L) == 0 || mpz_cmp (y, nm1) == 0) + return 1; + + for (i = 1; i < k; i++) + { + mpz_powm_ui (y, y, 2L, n); + if (mpz_cmp (y, nm1) == 0) + return 1; + if (mpz_cmp_ui (y, 1L) == 0) + return 0; + } + return 0; +} |