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Annotation of OpenXM_contrib/gmp/mpfr/random.c, Revision 1.1.1.2

1.1       maekawa     1: /* mpfr_random -- generate a random floating-point number
                      2:
1.1.1.2 ! ohara       3: Copyright 1999, 2001 Free Software Foundation, Inc.
1.1       maekawa     4:
                      5: This file is part of the MPFR Library.
                      6:
                      7: The MPFR Library is free software; you can redistribute it and/or modify
1.1.1.2 ! ohara       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
1.1       maekawa    10: option) any later version.
                     11:
                     12: The MPFR Library is distributed in the hope that it will be useful, but
                     13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2 ! ohara      14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    15: License for more details.
                     16:
1.1.1.2 ! ohara      17: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    18: along with the MPFR 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 <stdio.h>
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25: #include "longlong.h"
                     26: #include "mpfr.h"
1.1.1.2 ! ohara      27: #include "mpfr-impl.h"
1.1       maekawa    28:
1.1.1.2 ! ohara      29: /* Computes a random mpfr in [0, 1[ with precision MPFR_PREC */
1.1       maekawa    30:
                     31: void
1.1.1.2 ! ohara      32: mpfr_random (mpfr_ptr x)
1.1       maekawa    33: {
1.1.1.2 ! ohara      34:   mp_limb_t *xp; unsigned long xn, cnt, prec = MPFR_PREC(x);
1.1       maekawa    35:
1.1.1.2 ! ohara      36:   MPFR_CLEAR_FLAGS(x);
        !            37:   xp = MPFR_MANT(x);
1.1       maekawa    38:   xn = (prec-1)/BITS_PER_MP_LIMB + 1;
                     39:
1.1.1.2 ! ohara      40:   mpn_random (xp, xn);
1.1       maekawa    41:
1.1.1.2 ! ohara      42:   if (xp[xn - 1] == 0)
        !            43:     xp[xn - 1] = 1;
        !            44:   /* since count_leading_zeros doesn't like zeroes */
        !            45:
        !            46:   count_leading_zeros (cnt, xp[xn - 1]);
        !            47:   if (cnt)
        !            48:     mpn_lshift (xp, xp, xn, cnt);
        !            49:   MPFR_EXP(x) = -cnt;
        !            50:   if (MPFR_SIGN(x) < 0)
        !            51:     MPFR_CHANGE_SIGN(x);
1.1       maekawa    52:
1.1.1.2 ! ohara      53:   cnt = xn * BITS_PER_MP_LIMB - prec;
        !            54:   /* cnt is the number of non significant bits in the low limb */
        !            55:   xp[0] &= ~((MP_LIMB_T_ONE << cnt) - MP_LIMB_T_ONE);
1.1       maekawa    56: }