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/* mpfr_mul -- multiply two floating-point numbers
Copyright 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
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 Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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 Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser 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 "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
#include "mpfr-impl.h"
int
mpfr_mul (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
{
int sign_product, cc, inexact, ec, em = 0;
mp_exp_t bx, cx;
mp_limb_t *ap, *bp, *cp, *tmp;
mp_limb_t b1;
mp_prec_t aq, bq, cq;
mp_size_t an, bn, cn, tn, k;
TMP_DECL(marker);
/* deal with NaN and zero */
if (MPFR_IS_NAN(b) || MPFR_IS_NAN(c))
{
MPFR_SET_NAN(a);
MPFR_RET_NAN;
}
MPFR_CLEAR_NAN(a);
sign_product = MPFR_SIGN(b) * MPFR_SIGN(c);
if (MPFR_IS_INF(b))
{
if (MPFR_IS_INF(c) || MPFR_NOTZERO(c))
{
if (MPFR_SIGN(a) != sign_product)
MPFR_CHANGE_SIGN(a);
MPFR_SET_INF(a);
MPFR_RET(0); /* exact */
}
else
{
MPFR_SET_NAN(a);
MPFR_RET_NAN;
}
}
else if (MPFR_IS_INF(c))
{
if (MPFR_NOTZERO(b))
{
if (MPFR_SIGN(a) != sign_product)
MPFR_CHANGE_SIGN(a);
MPFR_SET_INF(a);
MPFR_RET(0); /* exact */
}
else
{
MPFR_SET_NAN(a);
MPFR_RET_NAN;
}
}
MPFR_ASSERTN(MPFR_IS_FP(b) && MPFR_IS_FP(c));
MPFR_CLEAR_INF(a); /* clear Inf flag */
if (MPFR_IS_ZERO(b) || MPFR_IS_ZERO(c))
{
if (MPFR_SIGN(a) != sign_product)
MPFR_CHANGE_SIGN(a);
MPFR_SET_ZERO(a);
MPFR_RET(0); /* 0 * 0 is exact */
}
bx = MPFR_EXP(b);
cx = MPFR_EXP(c);
/* Note: exponent of the result will be bx + cx + ec with ec in {-1,0,1} */
if (bx >= 0 && cx > 0)
{ /* bx + cx > 0 */
if (__mpfr_emax < 0 ||
(mp_exp_unsigned_t) bx + cx > (mp_exp_unsigned_t) __mpfr_emax + 1)
return mpfr_set_overflow(a, rnd_mode, sign_product);
if ((mp_exp_unsigned_t) bx + cx == (mp_exp_unsigned_t) __mpfr_emax + 1)
em = 1;
}
else if (bx <= 0 && cx < 0)
{ /* bx + cx < 0 */
if (__mpfr_emin > 0 ||
(mp_exp_unsigned_t) bx + cx < (mp_exp_unsigned_t) __mpfr_emin - 1)
return mpfr_set_underflow(a, rnd_mode, sign_product);
if ((mp_exp_unsigned_t) bx + cx == (mp_exp_unsigned_t) __mpfr_emin - 1)
em = -1;
}
else
{ /* bx != 0 and cx doesn't have the same sign */
if ((bx + cx) - 1 > __mpfr_emax)
return mpfr_set_overflow(a, rnd_mode, sign_product);
if ((bx + cx) - 1 == __mpfr_emax)
em = 1;
if ((bx + cx) + 1 < __mpfr_emin)
return mpfr_set_underflow(a, rnd_mode, sign_product);
if ((bx + cx) + 1 == __mpfr_emin)
em = -1;
}
ap = MPFR_MANT(a);
bp = MPFR_MANT(b);
cp = MPFR_MANT(c);
aq = MPFR_PREC(a);
bq = MPFR_PREC(b);
cq = MPFR_PREC(c);
an = (aq-1)/BITS_PER_MP_LIMB + 1; /* number of significant limbs of a */
bn = (bq-1)/BITS_PER_MP_LIMB + 1; /* number of significant limbs of b */
cn = (cq-1)/BITS_PER_MP_LIMB + 1; /* number of significant limbs of c */
MPFR_ASSERTN((mp_size_unsigned_t) bn + cn <= MP_SIZE_T_MAX);
k = bn + cn; /* effective nb of limbs used by b*c (= tn or tn+1) below */
MPFR_ASSERTN(bq + cq >= bq); /* no integer overflow */
tn = (bq + cq - 1) / BITS_PER_MP_LIMB + 1; /* <= k, thus no int overflow */
MPFR_ASSERTN(k <= ((size_t) -1) / BYTES_PER_MP_LIMB);
TMP_MARK(marker);
tmp = (mp_limb_t *) TMP_ALLOC((size_t) 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^(BITS_PER_MP_LIMB-2) */
b1 >>= BITS_PER_MP_LIMB - 1; /* msb from the product */
tmp += k - tn;
if (b1 == 0)
mpn_lshift (tmp, tmp, tn, 1);
cc = mpfr_round_raw (ap, tmp, bq + cq, sign_product < 0, aq,
rnd_mode, &inexact);
if (cc) /* cc = 1 ==> result is a power of two */
ap[an-1] = MP_LIMB_T_HIGHBIT;
TMP_FREE(marker);
ec = b1 - 1 + cc;
if (em == 0)
{
mp_exp_t ax = bx + cx;
if (ax == __mpfr_emax && ec > 0)
return mpfr_set_overflow(a, rnd_mode, sign_product);
if (ax == __mpfr_emin && ec < 0)
return mpfr_set_underflow(a, rnd_mode, sign_product);
MPFR_EXP(a) = ax + ec;
}
else if (em > 0)
{
if (ec >= 0)
return mpfr_set_overflow(a, rnd_mode, sign_product);
MPFR_EXP(a) = __mpfr_emax;
}
else
{
if (ec <= 0)
return mpfr_set_underflow(a, rnd_mode, sign_product);
MPFR_EXP(a) = __mpfr_emin;
}
if (MPFR_SIGN(a) != sign_product)
MPFR_CHANGE_SIGN(a);
return inexact;
}
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