63 lines
1.9 KiB
C
63 lines
1.9 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) 2008, 2009 William Hart
|
||
|
|
Copyright (C) 2009 Thomas Boothby
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "ulong_extras.h"
|
||
|
|
|
||
|
|
#define FLINT_ONE_LINE_MULTIPLIER 480
|
||
|
|
|
||
|
|
mp_limb_t n_factor_one_line(mp_limb_t n, ulong iters)
|
||
|
|
{
|
||
|
|
mp_limb_t orig_n = n, in, square, sqrti, mod, factor, factoring = iters, iin;
|
||
|
|
n *= FLINT_ONE_LINE_MULTIPLIER;
|
||
|
|
|
||
|
|
iin = 0;
|
||
|
|
in = n;
|
||
|
|
while (factoring && (iin < in))
|
||
|
|
{
|
||
|
|
sqrti = n_sqrt(in);
|
||
|
|
sqrti++;
|
||
|
|
square = sqrti*sqrti;
|
||
|
|
mod = square - in;
|
||
|
|
if (n_is_square(mod))
|
||
|
|
{
|
||
|
|
factor = n_sqrt(mod);
|
||
|
|
sqrti -= factor;
|
||
|
|
factor = n_gcd_full(orig_n, sqrti);
|
||
|
|
if (factor != UWORD(1))
|
||
|
|
{
|
||
|
|
return factor;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
factoring--;
|
||
|
|
iin = in;
|
||
|
|
in += n;
|
||
|
|
}
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
}
|