142 lines
3.6 KiB
C
142 lines
3.6 KiB
C
/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2008 Peter Shrimpton
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Copyright (C) 2009 William Hart
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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n_pair_t
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fchain_precomp(mp_limb_t m, mp_limb_t n, double npre)
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{
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n_pair_t current = {0, 0}, old;
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int length;
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mp_limb_t power, xy;
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old.x = UWORD(2);
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old.y = n - UWORD(3);
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length = FLINT_BIT_COUNT(m);
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power = (UWORD(1) << (length - 1));
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for (; length > 0; length--)
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{
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xy = n_mulmod_precomp(old.x, old.y, n, npre);
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xy = n_addmod(xy, UWORD(3), n);
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if (m & power)
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{
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current.y =
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n_submod(n_mulmod_precomp(old.y, old.y, n, npre), UWORD(2), n);
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current.x = xy;
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}
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else
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{
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current.x =
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n_submod(n_mulmod_precomp(old.x, old.x, n, npre), UWORD(2), n);
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current.y = xy;
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}
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power >>= 1;
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old = current;
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}
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return current;
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}
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n_pair_t
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fchain2_preinv(mp_limb_t m, mp_limb_t n, mp_limb_t ninv)
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{
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n_pair_t current = {0, 0}, old;
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int length;
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mp_limb_t power, xy;
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old.x = UWORD(2);
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old.y = n - UWORD(3);
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length = FLINT_BIT_COUNT(m);
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power = (UWORD(1) << (length - 1));
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for (; length > 0; length--)
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{
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xy = n_mulmod2_preinv(old.x, old.y, n, ninv);
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xy = n_addmod(xy, UWORD(3), n);
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if (m & power)
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{
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current.y =
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n_submod(n_mulmod2_preinv(old.y, old.y, n, ninv), UWORD(2), n);
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current.x = xy;
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}
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else
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{
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current.x =
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n_submod(n_mulmod2_preinv(old.x, old.x, n, ninv), UWORD(2), n);
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current.y = xy;
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}
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power >>= 1;
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old = current;
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}
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return current;
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}
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int
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n_is_probabprime_fibonacci(mp_limb_t n)
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{
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mp_limb_t m;
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n_pair_t V;
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if (FLINT_ABS((mp_limb_signed_t) n) <= UWORD(3))
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{
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if (n >= UWORD(2))
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return 1;
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return 0;
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}
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m = (n - n_jacobi(WORD(5), n)) / 2; /* cannot overflow
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as (5/n) = 0 for n = 2^64-1 */
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if (FLINT_BIT_COUNT(n) <= FLINT_D_BITS)
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{
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double npre = n_precompute_inverse(n);
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V = fchain_precomp(m, n, npre);
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return (n_mulmod_precomp(n - UWORD(3), V.x, n, npre) ==
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n_mulmod_precomp(UWORD(2), V.y, n, npre));
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}
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else
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{
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mp_limb_t ninv = n_preinvert_limb(n);
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V = fchain2_preinv(m, n, ninv);
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return (n_mulmod2_preinv(n - UWORD(3), V.x, n, ninv) ==
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n_mulmod2_preinv(UWORD(2), V.y, n, ninv));
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}
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}
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