pqc/external/flint-2.4.3/nmod_poly_mat/det_interpolate.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 <gmp.h>
#include "flint.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
#include "nmod_poly_mat.h"
void
nmod_poly_mat_det_interpolate(nmod_poly_t det, const nmod_poly_mat_t A)
{
slong i, l, n, len;
nmod_mat_t X;
mp_ptr x, d;
n = A->r;
if (n == 0)
{
nmod_poly_one(det);
return;
}
l = nmod_poly_mat_max_length(A);
if (l == 0)
{
nmod_poly_zero(det);
return;
}
/* Bound degree based on Laplace expansion */
len = n*(l - 1) + 1;
/* Not enough points to interpolate */
if (len > nmod_poly_mat_modulus(A))
{
nmod_poly_mat_det_fflu(det, A);
return;
}
x = _nmod_vec_init(len);
d = _nmod_vec_init(len);
nmod_mat_init(X, n, n, nmod_poly_mat_modulus(A));
for (i = 0; i < len; i++)
{
x[i] = i;
nmod_poly_mat_evaluate_nmod(X, A, x[i]);
d[i] = nmod_mat_det(X);
}
nmod_poly_interpolate_nmod_vec(det, x, d, len);
_nmod_vec_clear(x);
_nmod_vec_clear(d);
nmod_mat_clear(X);
}