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/* written by Paul Zimmermann, November 1998-January 1999 */
#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 mpfr_mul(a, b, c, rnd_mode)
mpfr_ptr a; mpfr_srcptr b, c; unsigned char rnd_mode;
{
unsigned int bn, cn, an, k; int cc;
mp_limb_t *ap, *bp=MANT(b), *cp=MANT(c), 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 = SIGN(b) * 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 */
k = bn+cn; /* effective nb of limbs used by b*c */
TMP_MARK(marker);
ap = (mp_limb_t*) TMP_ALLOC(k*BYTES_PER_MP_LIMB);
/* step 1: multiplies two mantissa */
if (bn>=cn) b1=mpn_mul(ap, bp, bn, cp, cn);
else b1=mpn_mul(ap, cp, cn, bp, bn);
/* now ap[0]..ap[k-1] contains the product of both mantissa,
with ap[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(ap, ap, k, 1);
cc = mpfr_round_raw(MANT(a), ap, rnd_mode, (sign_product<0) ? k ^ (1<<31) : k, PREC(a));
if (cc) { /* cc = 1 ==> result is a power of two */
MANT(a)[an-1] = (mp_limb_t) 1 << (BITS_PER_MP_LIMB-1);
}
EXP(a) = EXP(b) + EXP(c) + b1 - 1 + cc;
if (sign_product * SIGN(a)<0) CHANGE_SIGN(a);
TMP_FREE(marker);
return;
}
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