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

87 lines
2.1 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) 2010 Fredrik Johansson
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include "flint.h"
#include "ulong_extras.h"
#include "nmod_vec.h"
#include "nmod_mat.h"
#include "perm.h"
mp_limb_t
_nmod_mat_det(nmod_mat_t A)
{
mp_limb_t det;
slong * P;
slong m = A->r;
slong rank;
slong i;
P = flint_malloc(sizeof(slong) * m);
rank = nmod_mat_lu(P, A, 1);
det = UWORD(0);
if (rank == m)
{
det = UWORD(1);
for (i = 0; i < m; i++)
det = n_mulmod2_preinv(det, nmod_mat_entry(A, i, i),
A->mod.n, A->mod.ninv);
}
if (_perm_parity(P, m) == 1)
det = nmod_neg(det, A->mod);
flint_free(P);
return det;
}
mp_limb_t
nmod_mat_det(const nmod_mat_t A)
{
nmod_mat_t tmp;
mp_limb_t det;
slong dim = A->r;
if (dim != A->c)
{
flint_printf("Exception (nmod_mat_det). Non-square matrix.\n");
abort();
}
if (dim == 0) return UWORD(1);
if (dim == 1) return nmod_mat_entry(A, 0, 0);
nmod_mat_init_set(tmp, A);
det = _nmod_mat_det(tmp);
nmod_mat_clear(tmp);
return det;
}