100 lines
2.8 KiB
C
100 lines
2.8 KiB
C
|
/*=============================================================================
|
||
|
|
|
||
|
|
This file is part of FLINT.
|
||
|
|
|
||
|
|
FLINT is free software; you can redistribute it and/or modify
|
||
|
|
it under the terms of the GNU General Public License as published by
|
||
|
|
the Free Software Foundation; either version 2 of the License, or
|
||
|
|
(at your option) any later version.
|
||
|
|
|
||
|
|
FLINT 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 General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU General Public License
|
||
|
|
along with FLINT; if not, write to the Free Software
|
||
|
|
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
|
||
|
|
|
||
|
|
=============================================================================*/
|
||
|
|
/******************************************************************************
|
||
|
|
|
||
|
|
Copyright (C) 2009 William Hart
|
||
|
|
Copyright (C) 2012 Fredrik Johansson
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "ulong_extras.h"
|
||
|
|
#include "fmpz.h"
|
||
|
|
|
||
|
|
void
|
||
|
|
fmpz_mul_si_tdiv_q_2exp(fmpz_t f, const fmpz_t g, slong x, ulong exp)
|
||
|
|
{
|
||
|
|
fmpz c2 = *g;
|
||
|
|
|
||
|
|
if (x == 0)
|
||
|
|
{
|
||
|
|
fmpz_zero(f);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
else if (!COEFF_IS_MPZ(c2)) /* c2 is small */
|
||
|
|
{
|
||
|
|
mp_limb_t prod[2];
|
||
|
|
mp_limb_t uc2;
|
||
|
|
mp_limb_t ux;
|
||
|
|
|
||
|
|
if (exp >= 2 * FLINT_BITS)
|
||
|
|
{
|
||
|
|
fmpz_zero(f);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
uc2 = FLINT_ABS(c2);
|
||
|
|
ux = FLINT_ABS(x);
|
||
|
|
|
||
|
|
umul_ppmm(prod[1], prod[0], uc2, ux);
|
||
|
|
|
||
|
|
if (exp >= FLINT_BITS)
|
||
|
|
{
|
||
|
|
fmpz_set_ui(f, prod[1] >> (exp - FLINT_BITS));
|
||
|
|
if ((c2 ^ x) < WORD(0))
|
||
|
|
fmpz_neg(f, f);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (exp != 0)
|
||
|
|
{
|
||
|
|
prod[0] = (prod[1] << (FLINT_BITS - exp)) | (prod[0] >> exp);
|
||
|
|
prod[1] >>= exp;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (!prod[1])
|
||
|
|
{
|
||
|
|
fmpz_set_ui(f, prod[0]);
|
||
|
|
if ((c2 ^ x) < WORD(0))
|
||
|
|
fmpz_neg(f, f);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
else /* result takes two limbs */
|
||
|
|
{
|
||
|
|
__mpz_struct *mpz_ptr = _fmpz_promote(f);
|
||
|
|
|
||
|
|
/* two limbs, least significant first, native endian, no
|
||
|
|
nails, stored in prod */
|
||
|
|
mpz_import(mpz_ptr, 2, -1, sizeof(mp_limb_t), 0, 0, prod);
|
||
|
|
if ((c2 ^ x) < WORD(0))
|
||
|
|
mpz_neg(mpz_ptr, mpz_ptr);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
else /* c2 is large */
|
||
|
|
{
|
||
|
|
__mpz_struct *mpz_ptr = _fmpz_promote(f); /* ok without val as
|
||
|
|
if aliased both are large */
|
||
|
|
flint_mpz_mul_si(mpz_ptr, COEFF_TO_PTR(c2), x);
|
||
|
|
mpz_tdiv_q_2exp(mpz_ptr, mpz_ptr, exp);
|
||
|
|
_fmpz_demote_val(f); /* value may be small */
|
||
|
|
}
|
||
|
|
}
|