pqc/external/flint-2.4.3/fmpq/reconstruct_fmpz.c
2014-05-24 23:16:06 +02:00

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