Annotation of OpenXM_contrib/gmp/mpz/urandomm.c, Revision 1.1
1.1 ! maekawa 1: /* mpz_urandomm (rop, state, n) -- Generate a uniform pseudorandom
! 2: integer in the range 0 to N-1, using STATE as the random state
! 3: previously initialized by a call to gmp_randinit().
! 4:
! 5: Copyright (C) 2000 Free Software Foundation, Inc.
! 6:
! 7: This file is part of the GNU MP Library.
! 8:
! 9: The GNU MP Library is free software; you can redistribute it and/or modify
! 10: it under the terms of the GNU Lesser General Public License as published by
! 11: the Free Software Foundation; either version 2.1 of the License, or (at your
! 12: option) any later version.
! 13:
! 14: The GNU MP Library is distributed in the hope that it will be useful, but
! 15: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
! 16: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
! 17: License for more details.
! 18:
! 19: You should have received a copy of the GNU Lesser General Public License
! 20: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
! 21: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
! 22: MA 02111-1307, USA. */
! 23:
! 24: #include "gmp.h"
! 25: #include "gmp-impl.h"
! 26: #include "longlong.h"
! 27:
! 28: void
! 29: #if __STDC__
! 30: mpz_urandomm (mpz_t rop, gmp_randstate_t rstate, mpz_t n)
! 31: #else
! 32: mpz_urandomm (rop, rstate, n)
! 33: mpz_t rop;
! 34: gmp_randstate_t rstate;
! 35: mpz_t n;
! 36: #endif
! 37: {
! 38: mpz_t t, p, m;
! 39: mp_ptr tp;
! 40: mp_size_t nbits, size;
! 41: int count;
! 42:
! 43: /* FIXME: Should check for n == 0 and report error */
! 44:
! 45: size = SIZ (n);
! 46: count_leading_zeros (count, PTR (n)[size - 1]);
! 47: nbits = size * BITS_PER_MP_LIMB - count;
! 48:
! 49: /* Allocate enough for any mpz function called since a realloc of
! 50: these will fail. */
! 51: MPZ_TMP_INIT (t, size);
! 52: MPZ_TMP_INIT (m, size + 1);
! 53: MPZ_TMP_INIT (p, size + 1);
! 54:
! 55: /* Let m = highest possible random number plus 1. */
! 56: mpz_set_ui (m, 0);
! 57: mpz_setbit (m, nbits);
! 58:
! 59: /* Let p = floor(m / n) * n. */
! 60: mpz_fdiv_q (p, m, n);
! 61: mpz_mul (p, p, n);
! 62:
! 63: tp = PTR (t);
! 64: do
! 65: {
! 66: _gmp_rand (tp, rstate, nbits);
! 67: MPN_NORMALIZE (tp, size); /* FIXME: Really necessary? */
! 68: SIZ (t) = size;
! 69: }
! 70: while (mpz_cmp (t, p) >= 0);
! 71:
! 72: mpz_mod (rop, t, n);
! 73: }
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