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

1.1     ! maekawa     1: /* mpfr_add_one_ulp, mpfr_sub_one_ulp -- add/subtract one unit in last place
        !             2:
        !             3: Copyright (C) 1999 PolKA project, Inria Lorraine and Loria
        !             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
        !             8: it under the terms of the GNU Library General Public License as published by
        !             9: the Free Software Foundation; either version 2 of the License, or (at your
        !            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
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Library General Public License
        !            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 "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24: #include "mpfr.h"
        !            25:
        !            26: /* sets x to x+sign(x)*2^(EXP(x)-PREC(x)) */
        !            27: int
        !            28: #if __STDC__
        !            29: mpfr_add_one_ulp(mpfr_ptr x)
        !            30: #else
        !            31: mpfr_add_one_ulp(x)
        !            32:      mpfr_ptr x;
        !            33: #endif
        !            34: {
        !            35:   int xn, sh; mp_limb_t *xp;
        !            36:
        !            37:   xn = 1 + (PREC(x)-1)/BITS_PER_MP_LIMB;
        !            38:   sh = xn*BITS_PER_MP_LIMB - PREC(x);
        !            39:   xp = MANT(x);
        !            40:   if (mpn_add_1(xp, xp, xn, (mp_limb_t)1<<sh)) {
        !            41:     EXP(x)++;
        !            42:     mpn_rshift(xp, xp, xn, 1);
        !            43:     xp[xn-1] += (mp_limb_t)1<<(BITS_PER_MP_LIMB-1);
        !            44:   }
        !            45:   return 0;
        !            46: }
        !            47:
        !            48: /* sets x to x-sign(x)*ulp(x) */
        !            49: int mpfr_sub_one_ulp(mpfr_ptr x)
        !            50: {
        !            51:   int xn, sh; mp_limb_t *xp;
        !            52:
        !            53:   xn = 1 + (PREC(x)-1)/BITS_PER_MP_LIMB;
        !            54:   sh = xn*BITS_PER_MP_LIMB-PREC(x);
        !            55:   xp = MANT(x);
        !            56:   mpn_sub_1(xp, xp, xn, (mp_limb_t)1<<sh);
        !            57:   if (xp[xn-1] >> (BITS_PER_MP_LIMB-1) == 0) {
        !            58:     /* was an exact power of two: not normalized any more */
        !            59:     EXP(x)--;
        !            60:     mpn_lshift(xp, xp, xn, 1);
        !            61:     *xp |= ((mp_limb_t)1 << sh);
        !            62:   }
        !            63:   return 0;
        !            64: }