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/* mpfr_mul -- multiply two floating-point numbers
Copyright (C) 1999 PolKA project, Inria Lorraine and Loria
This file is part of the MPFR Library.
The MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include <stdio.h>
#include "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
/* Remains to do:
- do not use all bits of b and c when PREC(b)>PREC(a) or PREC(c)>PREC(a)
[current complexity is O(PREC(b)*PREC(c))]
*/
void
#if __STDC__
mpfr_mul(mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
#else
mpfr_mul(a, b, c, rnd_mode)
mpfr_ptr a;
mpfr_srcptr b;
mpfr_srcptr c;
mp_rnd_t rnd_mode;
#endif
{
unsigned int bn, cn, an, tn, k; int cc;
mp_limb_t *ap=MANT(a), *bp=MANT(b), *cp=MANT(c), *tmp, b1;
long int sign_product;
TMP_DECL(marker);
/* deal with NaN and zero */
if (FLAG_NAN(b) || FLAG_NAN(c)) { SET_NAN(a); return; }
if (!NOTZERO(b) || !NOTZERO(c)) { SET_ZERO(a); return; }
sign_product = MPFR_SIGN(b) * MPFR_SIGN(c);
bn = (PREC(b)-1)/mp_bits_per_limb+1; /* number of significant limbs of b */
cn = (PREC(c)-1)/mp_bits_per_limb+1; /* number of significant limbs of c */
tn = (PREC(c)+PREC(b)-1)/mp_bits_per_limb+1;
k = bn+cn; /* effective nb of limbs used by b*c */
TMP_MARK(marker);
tmp = (mp_limb_t*) TMP_ALLOC(k*BYTES_PER_MP_LIMB);
/* multiplies two mantissa in temporary allocated space */
b1 = (bn>=cn) ? mpn_mul(tmp, bp, bn, cp, cn) : mpn_mul(tmp, cp, cn, bp, bn);
/* now tmp[0]..tmp[k-1] contains the product of both mantissa,
with tmp[k-1]>=2^(mp_bits_per_limb-2) */
an = (PREC(a)-1)/mp_bits_per_limb+1; /* number of significant limbs of a */
b1 >>= mp_bits_per_limb-1; /* msb from the product */
if (b1==0) mpn_lshift(tmp, tmp, k, 1);
cc = mpfr_round_raw(ap, tmp+bn+cn-tn,
PREC(b)+PREC(c), (sign_product<0), PREC(a), rnd_mode);
if (cc) { /* cc = 1 ==> result is a power of two */
ap[an-1] = (mp_limb_t) 1 << (BITS_PER_MP_LIMB-1);
}
EXP(a) = EXP(b) + EXP(c) + b1 - 1 + cc;
if (sign_product * MPFR_SIGN(a)<0) CHANGE_SIGN(a);
TMP_FREE(marker);
return;
}
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