117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
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/*=============================================================================
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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) 2011 Fredrik Johansson
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******************************************************************************/
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#include "fmpq.h"
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#define ROT(u,v,t) \
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do { fmpz _t = *u; *u = *v; *v = *t; *t = _t; } while (0);
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int
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_fmpq_reconstruct_fmpz_2(fmpz_t n, fmpz_t d,
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const fmpz_t a, const fmpz_t m, const fmpz_t N, const fmpz_t D)
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{
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fmpz_t q, r, s, t;
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int success = 0;
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/* Quickly identify small integers */
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if (fmpz_cmp(a, N) <= 0)
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{
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fmpz_set(n, a);
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fmpz_one(d);
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return 1;
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}
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fmpz_sub(n, a, m);
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if (fmpz_cmpabs(n, N) <= 0)
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{
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fmpz_one(d);
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return 1;
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}
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fmpz_init(q);
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fmpz_init(r);
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fmpz_init(s);
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fmpz_init(t);
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fmpz_set(r, m); fmpz_zero(s);
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fmpz_set(n, a); fmpz_one(d);
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while (fmpz_cmpabs(n, N) > 0)
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{
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fmpz_fdiv_q(q, r, n);
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fmpz_mul(t, q, n); fmpz_sub(t, r, t); ROT(r, n, t);
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fmpz_mul(t, q, d); fmpz_sub(t, s, t); ROT(s, d, t);
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}
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if (fmpz_sgn(d) < 0)
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{
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fmpz_neg(n, n);
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fmpz_neg(d, d);
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}
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if (fmpz_cmp(d, D) <= 0)
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{
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fmpz_gcd(t, n, d);
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success = fmpz_is_one(t);
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}
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fmpz_clear(q);
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fmpz_clear(r);
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fmpz_clear(s);
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fmpz_clear(t);
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return success;
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}
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int
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fmpq_reconstruct_fmpz_2(fmpq_t res, const fmpz_t a, const fmpz_t m,
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const fmpz_t N, const fmpz_t D)
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{
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return _fmpq_reconstruct_fmpz_2(fmpq_numref(res),
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fmpq_denref(res), a, m, N, D);
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}
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int
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_fmpq_reconstruct_fmpz(fmpz_t n, fmpz_t d,
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const fmpz_t a, const fmpz_t m)
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{
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fmpz_t N;
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int result;
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fmpz_init(N);
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fmpz_fdiv_q_2exp(N, m, 1);
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fmpz_sqrt(N, N);
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result = _fmpq_reconstruct_fmpz_2(n, d, a, m, N, N);
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fmpz_clear(N);
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return result;
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}
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int
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fmpq_reconstruct_fmpz(fmpq_t res, const fmpz_t a, const fmpz_t m)
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{
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return _fmpq_reconstruct_fmpz(fmpq_numref(res),
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fmpq_denref(res), a, m);
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}
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