101 lines
2.6 KiB
C
101 lines
2.6 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) 2009 William Hart
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Copyright (C) 2011 Fredrik Johansson
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******************************************************************************/
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#include <stdlib.h>
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#include <stdio.h>
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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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#include "fmpz.h"
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void
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_fmpz_CRT_ui_precomp(fmpz_t out, const fmpz_t r1, const fmpz_t m1, ulong r2,
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ulong m2, mp_limb_t m2inv, const fmpz_t m1m2, mp_limb_t c, int sign)
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{
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mp_limb_t r1mod, s;
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fmpz_t r1normal;
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fmpz_t tmp;
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fmpz_init(tmp);
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/* FIXME: assume r1 moved to [0, m1); add tests for this */
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if (fmpz_sgn(r1) < 0)
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{
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fmpz_init(r1normal);
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fmpz_add(r1normal, r1, m1);
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}
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else
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{
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*r1normal = *r1;
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}
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r1mod = fmpz_fdiv_ui(r1normal, m2);
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s = n_submod(r2, r1mod, m2);
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s = n_mulmod2_preinv(s, c, m2, m2inv);
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fmpz_mul_ui(tmp, m1, s);
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fmpz_add(tmp, tmp, r1normal);
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if (fmpz_sgn(r1) < 0)
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fmpz_clear(r1normal);
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if (sign)
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{
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fmpz_sub(out, tmp, m1m2);
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if (fmpz_cmpabs(tmp, out) <= 0)
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fmpz_set(out, tmp);
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}
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else
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{
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fmpz_set(out, tmp);
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}
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fmpz_clear(tmp);
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}
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void fmpz_CRT_ui(fmpz_t out, const fmpz_t r1, const fmpz_t m1,
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ulong r2, ulong m2, int sign)
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{
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mp_limb_t c;
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fmpz_t m1m2;
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c = fmpz_fdiv_ui(m1, m2);
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c = n_invmod(c, m2);
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if (c == 0)
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{
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flint_printf("Exception (fmpz_CRT_ui). m1 not invertible modulo m2.\n");
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abort();
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}
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fmpz_init(m1m2);
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fmpz_mul_ui(m1m2, m1, m2);
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_fmpz_CRT_ui_precomp(out, r1, m1, r2, m2, n_preinvert_limb(m2),
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m1m2, c, sign);
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fmpz_clear(m1m2);
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}
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