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

1.1     ! maekawa     1: /* mpfr_mul -- multiply two floating-point numbers
        !             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 <stdio.h>
        !            23: #include "gmp.h"
        !            24: #include "gmp-impl.h"
        !            25: #include "mpfr.h"
        !            26:
        !            27: /* Remains to do:
        !            28: - do not use all bits of b and c when PREC(b)>PREC(a) or PREC(c)>PREC(a)
        !            29:   [current complexity is O(PREC(b)*PREC(c))]
        !            30: */
        !            31:
        !            32: void
        !            33: #if __STDC__
        !            34: mpfr_mul(mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, unsigned char rnd_mode)
        !            35: #else
        !            36: mpfr_mul(a, b, c, rnd_mode)
        !            37:      mpfr_ptr a;
        !            38:      mpfr_srcptr b;
        !            39:      mpfr_srcptr c;
        !            40:      unsigned char rnd_mode;
        !            41: #endif
        !            42: {
        !            43:   unsigned int bn, cn, an, tn, k; int cc;
        !            44:   mp_limb_t *ap=MANT(a), *bp=MANT(b), *cp=MANT(c), *tmp, b1;
        !            45:   long int sign_product;
        !            46:   TMP_DECL(marker);
        !            47:
        !            48:   /* deal with NaN and zero */
        !            49:   if (FLAG_NAN(b) || FLAG_NAN(c)) { SET_NAN(a); return; }
        !            50:   if (!NOTZERO(b) || !NOTZERO(c)) { SET_ZERO(a); return; }
        !            51:
        !            52:   sign_product = SIGN(b) * SIGN(c);
        !            53:   bn = (PREC(b)-1)/mp_bits_per_limb+1; /* number of significant limbs of b */
        !            54:   cn = (PREC(c)-1)/mp_bits_per_limb+1; /* number of significant limbs of c */
        !            55:   tn = (PREC(c)+PREC(b)-1)/mp_bits_per_limb+1;
        !            56:   k = bn+cn; /* effective nb of limbs used by b*c */
        !            57:   TMP_MARK(marker);
        !            58:   tmp = (mp_limb_t*) TMP_ALLOC(k*BYTES_PER_MP_LIMB);
        !            59:
        !            60:   /* multiplies two mantissa in temporary allocated space */
        !            61:   b1 = (bn>=cn) ? mpn_mul(tmp, bp, bn, cp, cn) : mpn_mul(tmp, cp, cn, bp, bn);
        !            62:
        !            63:   /* now tmp[0]..tmp[k-1] contains the product of both mantissa,
        !            64:      with tmp[k-1]>=2^(mp_bits_per_limb-2) */
        !            65:   an = (PREC(a)-1)/mp_bits_per_limb+1; /* number of significant limbs of a */
        !            66:   b1 >>= mp_bits_per_limb-1; /* msb from the product */
        !            67:
        !            68:   if (b1==0) mpn_lshift(tmp, tmp, k, 1);
        !            69:   cc = mpfr_round_raw(ap, tmp+bn+cn-tn,
        !            70:                      PREC(b)+PREC(c), (sign_product<0), PREC(a), rnd_mode);
        !            71:   if (cc) { /* cc = 1 ==> result is a power of two */
        !            72:     ap[an-1] = (mp_limb_t) 1 << (BITS_PER_MP_LIMB-1);
        !            73:   }
        !            74:   EXP(a) = EXP(b) + EXP(c) + b1 - 1 + cc;
        !            75:   if (sign_product * SIGN(a)<0) CHANGE_SIGN(a);
        !            76:   TMP_FREE(marker);
        !            77:   return;
        !            78: }