pqc/external/flint-2.4.3/fmpq/set_cfrac.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) 2011 Fredrik Johansson
******************************************************************************/
#include "fmpq.h"
#include "fmpz_mat.h"
void
_fmpq_set_cfrac_basecase(fmpz_t p, fmpz_t t, fmpz_t q, fmpz_t u,
const fmpz * c, slong n)
{
slong i;
fmpz_set(p, c);
fmpz_one(q);
fmpz_one(t);
fmpz_zero(u);
for (i = 1; i < n; i++)
{
fmpz_addmul(t, c + i, p);
fmpz_addmul(u, c + i, q);
fmpz_swap(t, p);
fmpz_swap(u, q);
}
}
void
_fmpq_set_cfrac_divconquer(fmpz_mat_t P, const fmpz * c, slong n)
{
if (n < 32)
{
_fmpq_set_cfrac_basecase(
fmpz_mat_entry(P, 0, 0), fmpz_mat_entry(P, 0, 1),
fmpz_mat_entry(P, 1, 0), fmpz_mat_entry(P, 1, 1), c, n);
}
else
{
fmpz_mat_t L, R;
slong m = n / 2;
fmpz_mat_init(L, 2, 2);
fmpz_mat_init(R, 2, 2);
_fmpq_set_cfrac_divconquer(L, c, m);
_fmpq_set_cfrac_divconquer(R, c + m, n - m);
fmpz_mat_mul_classical(P, L, R); /* Should be Strassen */
fmpz_mat_clear(L);
fmpz_mat_clear(R);
}
}
void
fmpq_set_cfrac(fmpq_t x, const fmpz * c, slong n)
{
if (n <= 64)
{
fmpz_t t, u;
fmpz_init(t);
fmpz_init(u);
_fmpq_set_cfrac_basecase(fmpq_numref(x), t, fmpq_denref(x), u, c, n);
fmpz_clear(t);
fmpz_clear(u);
}
else
{
fmpz_mat_t P;
fmpz_mat_init(P, 2, 2);
_fmpq_set_cfrac_divconquer(P, c, n);
fmpz_set(fmpq_numref(x), fmpz_mat_entry(P, 0, 0));
fmpz_set(fmpq_denref(x), fmpz_mat_entry(P, 1, 0));
fmpz_mat_clear(P);
}
}