113 lines
2.9 KiB
C
113 lines
2.9 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) 2012 Fredrik Johansson
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "ulong_extras.h"
|
||
|
|
#include "fmpz.h"
|
||
|
|
|
||
|
|
mp_limb_t
|
||
|
|
fmpz_abs_ubound_ui_2exp(slong * exp, const fmpz_t x, int bits)
|
||
|
|
{
|
||
|
|
mp_limb_t m;
|
||
|
|
slong shift, e, size;
|
||
|
|
fmpz c = *x;
|
||
|
|
|
||
|
|
if (!COEFF_IS_MPZ(c))
|
||
|
|
{
|
||
|
|
m = FLINT_ABS(c);
|
||
|
|
e = 0;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
/* mpz */
|
||
|
|
__mpz_struct * z = COEFF_TO_PTR(c);
|
||
|
|
size = z->_mp_size;
|
||
|
|
size = FLINT_ABS(size);
|
||
|
|
e = (size - 1) * FLINT_BITS;
|
||
|
|
|
||
|
|
if (size == 1)
|
||
|
|
{
|
||
|
|
m = z->_mp_d[0];
|
||
|
|
}
|
||
|
|
else /* there are two or more limbs */
|
||
|
|
{
|
||
|
|
/* top limb (which must be nonzero) */
|
||
|
|
m = z->_mp_d[size - 1];
|
||
|
|
|
||
|
|
count_leading_zeros(shift, m);
|
||
|
|
shift = FLINT_BITS - shift - bits;
|
||
|
|
e += shift;
|
||
|
|
|
||
|
|
if (shift >= 0)
|
||
|
|
{
|
||
|
|
/* round up */
|
||
|
|
m = (m >> shift) + 1;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
/* read a second limb to get an accurate value */
|
||
|
|
mp_limb_t m2 = z->_mp_d[size - 2];
|
||
|
|
m = (m << (-shift)) | (m2 >> (FLINT_BITS + shift));
|
||
|
|
/* round up */
|
||
|
|
m++;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* adding 1 caused overflow to the next power of two */
|
||
|
|
if ((m & (m - UWORD(1))) == UWORD(0))
|
||
|
|
{
|
||
|
|
m = UWORD(1) << (bits - 1);
|
||
|
|
e++;
|
||
|
|
}
|
||
|
|
|
||
|
|
*exp = e;
|
||
|
|
return m;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* single limb, adjust */
|
||
|
|
count_leading_zeros(shift, m);
|
||
|
|
e = FLINT_BITS - shift - bits;
|
||
|
|
|
||
|
|
if (e >= 0)
|
||
|
|
{
|
||
|
|
m = (m >> e) + 1;
|
||
|
|
|
||
|
|
/* overflowed to next power of two */
|
||
|
|
if ((m & (m - 1)) == UWORD(0))
|
||
|
|
{
|
||
|
|
m = UWORD(1) << (bits - 1);
|
||
|
|
e++;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
m <<= (-e);
|
||
|
|
}
|
||
|
|
|
||
|
|
*exp = e;
|
||
|
|
return m;
|
||
|
|
}
|