86 lines
2.4 KiB
C
86 lines
2.4 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
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "ulong_extras.h"
|
||
|
|
#include "fmpz.h"
|
||
|
|
|
||
|
|
ulong
|
||
|
|
z_gcd(slong a, slong b)
|
||
|
|
{
|
||
|
|
ulong ua = FLINT_ABS(a);
|
||
|
|
ulong ub = FLINT_ABS(b);
|
||
|
|
|
||
|
|
return n_gcd_full(ua, ub);
|
||
|
|
}
|
||
|
|
|
||
|
|
void
|
||
|
|
fmpz_gcd(fmpz_t f, const fmpz_t g, const fmpz_t h)
|
||
|
|
{
|
||
|
|
fmpz c1 = *g;
|
||
|
|
fmpz c2 = *h;
|
||
|
|
|
||
|
|
if (fmpz_is_zero(g))
|
||
|
|
{
|
||
|
|
fmpz_abs(f, h);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (fmpz_is_zero(h))
|
||
|
|
{
|
||
|
|
fmpz_abs(f, g);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (!COEFF_IS_MPZ(c1)) /* g is small */
|
||
|
|
{
|
||
|
|
if (!COEFF_IS_MPZ(c2)) /* h is also small */
|
||
|
|
{
|
||
|
|
fmpz_set_si(f, z_gcd(c1, c2));
|
||
|
|
}
|
||
|
|
else /* h is large, but g is small */
|
||
|
|
{
|
||
|
|
fmpz c2d = fmpz_fdiv_ui(h, FLINT_ABS(c1));
|
||
|
|
fmpz_set_si(f, z_gcd(c1, c2d));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
if (!COEFF_IS_MPZ(c2)) /* h is small, but g is large */
|
||
|
|
{
|
||
|
|
fmpz c1d = fmpz_fdiv_ui(g, FLINT_ABS(c2));
|
||
|
|
fmpz_set_si(f, z_gcd(c2, c1d));
|
||
|
|
}
|
||
|
|
else /* g and h are both large */
|
||
|
|
{
|
||
|
|
__mpz_struct *mpz_ptr = _fmpz_promote(f); /* aliasing fine as g, h already large */
|
||
|
|
|
||
|
|
mpz_gcd(mpz_ptr, COEFF_TO_PTR(c1), COEFF_TO_PTR(c2));
|
||
|
|
_fmpz_demote_val(f); /* gcd may be small */
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|