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Annotation of OpenXM_contrib/gmp/mpfr/urandomb.c, Revision 1.1

1.1     ! ohara       1: /* mpfr_urandomb (rop, state, nbits) -- Generate a uniform pseudorandom
        !             2:    real number between 0 (inclusive) and 1 (exclusive) of size NBITS,
        !             3:    using STATE as the random state previously initialized by a call to
        !             4:    gmp_randinit().
        !             5:
        !             6: Copyright 2000, 2001 Free Software Foundation, Inc.
        !             7:
        !             8: This file is part of the MPFR Library.
        !             9:
        !            10: The MPFR Library is free software; you can redistribute it and/or modify
        !            11: it under the terms of the GNU Lesser General Public License as published by
        !            12: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            13: option) any later version.
        !            14:
        !            15: The MPFR Library is distributed in the hope that it will be useful, but
        !            16: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            17: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            18: License for more details.
        !            19:
        !            20: You should have received a copy of the GNU Lesser General Public License
        !            21: along with the MPFR Library; see the file COPYING.LIB.  If not, write to
        !            22: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            23: MA 02111-1307, USA. */
        !            24:
        !            25: #include <stdio.h>
        !            26: #include "gmp.h"
        !            27: #include "gmp-impl.h"
        !            28: #include "longlong.h"
        !            29: #include "mpfr.h"
        !            30: #include "mpfr-impl.h"
        !            31:
        !            32: void
        !            33: mpfr_urandomb (mpfr_ptr rop, gmp_randstate_t rstate)
        !            34: {
        !            35:   mp_ptr rp;
        !            36:   mp_size_t nlimbs;
        !            37:   mp_exp_t exp;
        !            38:   unsigned long cnt, nbits;
        !            39:
        !            40:   MPFR_CLEAR_FLAGS(rop);
        !            41:
        !            42:   rp = MPFR_MANT(rop);
        !            43:   nbits = MPFR_PREC(rop);
        !            44:   nlimbs = (nbits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB;
        !            45:
        !            46:   _gmp_rand (rp, rstate, nbits);
        !            47:
        !            48:   /* If nbits isn't a multiple of BITS_PER_MP_LIMB, shift up.  */
        !            49:   if (nlimbs != 0)
        !            50:     {
        !            51:       if (nbits % BITS_PER_MP_LIMB != 0)
        !            52:        mpn_lshift (rp, rp, nlimbs,
        !            53:                    BITS_PER_MP_LIMB - nbits % BITS_PER_MP_LIMB);
        !            54:     }
        !            55:
        !            56:   exp = 0;
        !            57:   while (nlimbs != 0 && rp[nlimbs - 1] == 0)
        !            58:     {
        !            59:       nlimbs--;
        !            60:       exp--;
        !            61:     }
        !            62:
        !            63:   count_leading_zeros (cnt, rp[nlimbs - 1]);
        !            64:   if (cnt) mpn_lshift (rp, rp, nlimbs, cnt);
        !            65:   exp -= cnt;
        !            66:
        !            67:   cnt = nlimbs*BITS_PER_MP_LIMB - nbits;
        !            68:   /* cnt is the number of non significant bits in the low limb */
        !            69:   rp[0] &= ~((MP_LIMB_T_ONE << cnt) - 1);
        !            70:
        !            71:   MPFR_EXP (rop) = exp;
        !            72: }