pqc/external/flint-2.4.3/ulong_extras/is_probabprime_fibonacci.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
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 Peter Shrimpton
Copyright (C) 2009 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "ulong_extras.h"
n_pair_t
fchain_precomp(mp_limb_t m, mp_limb_t n, double npre)
{
n_pair_t current = {0, 0}, old;
int length;
mp_limb_t power, xy;
old.x = UWORD(2);
old.y = n - UWORD(3);
length = FLINT_BIT_COUNT(m);
power = (UWORD(1) << (length - 1));
for (; length > 0; length--)
{
xy = n_mulmod_precomp(old.x, old.y, n, npre);
xy = n_addmod(xy, UWORD(3), n);
if (m & power)
{
current.y =
n_submod(n_mulmod_precomp(old.y, old.y, n, npre), UWORD(2), n);
current.x = xy;
}
else
{
current.x =
n_submod(n_mulmod_precomp(old.x, old.x, n, npre), UWORD(2), n);
current.y = xy;
}
power >>= 1;
old = current;
}
return current;
}
n_pair_t
fchain2_preinv(mp_limb_t m, mp_limb_t n, mp_limb_t ninv)
{
n_pair_t current = {0, 0}, old;
int length;
mp_limb_t power, xy;
old.x = UWORD(2);
old.y = n - UWORD(3);
length = FLINT_BIT_COUNT(m);
power = (UWORD(1) << (length - 1));
for (; length > 0; length--)
{
xy = n_mulmod2_preinv(old.x, old.y, n, ninv);
xy = n_addmod(xy, UWORD(3), n);
if (m & power)
{
current.y =
n_submod(n_mulmod2_preinv(old.y, old.y, n, ninv), UWORD(2), n);
current.x = xy;
}
else
{
current.x =
n_submod(n_mulmod2_preinv(old.x, old.x, n, ninv), UWORD(2), n);
current.y = xy;
}
power >>= 1;
old = current;
}
return current;
}
int
n_is_probabprime_fibonacci(mp_limb_t n)
{
mp_limb_t m;
n_pair_t V;
if (FLINT_ABS((mp_limb_signed_t) n) <= UWORD(3))
{
if (n >= UWORD(2))
return 1;
return 0;
}
m = (n - n_jacobi(WORD(5), n)) / 2; /* cannot overflow
as (5/n) = 0 for n = 2^64-1 */
if (FLINT_BIT_COUNT(n) <= FLINT_D_BITS)
{
double npre = n_precompute_inverse(n);
V = fchain_precomp(m, n, npre);
return (n_mulmod_precomp(n - UWORD(3), V.x, n, npre) ==
n_mulmod_precomp(UWORD(2), V.y, n, npre));
}
else
{
mp_limb_t ninv = n_preinvert_limb(n);
V = fchain2_preinv(m, n, ninv);
return (n_mulmod2_preinv(n - UWORD(3), V.x, n, ninv) ==
n_mulmod2_preinv(UWORD(2), V.y, n, ninv));
}
}