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Annotation of OpenXM_contrib/gmp/mpfr/mul.c, Revision 1.1.1.1

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: }