pqc/external/flint-2.4.3/nmod_mat/inv.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) 2010 Fredrik Johansson
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include "flint.h"
#include "ulong_extras.h"
#include "nmod_vec.h"
#include "nmod_mat.h"
int nmod_mat_inv(nmod_mat_t B, const nmod_mat_t A)
{
nmod_mat_t I;
slong i, dim;
int result;
dim = A->r;
switch (dim)
{
case 0:
result = 1;
break;
case 1:
if (nmod_mat_entry(A, 0, 0) == UWORD(0))
{
result = 0;
}
else
{
nmod_mat_entry(B, 0, 0) =
n_invmod(nmod_mat_entry(A, 0, 0), B->mod.n);
result = 1;
}
break;
default:
nmod_mat_init(I, dim, dim, B->mod.n);
for (i = 0; i < dim; i++)
nmod_mat_entry(I, i, i) = UWORD(1);
result = nmod_mat_solve(B, A, I);
nmod_mat_clear(I);
}
return result;
}