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

113 lines
3.0 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 "flint.h"
#include "nmod_poly.h"
#include "nmod_poly_mat.h"
#define E(j,k) nmod_poly_mat_entry(B,j,k)
static __inline__ void
nmod_poly_mat_swap_rows(nmod_poly_mat_t mat, slong * perm, slong r, slong s)
{
if (r != s)
{
nmod_poly_struct * u;
slong t;
if (perm)
{
t = perm[s];
perm[s] = perm[r];
perm[r] = t;
}
u = mat->rows[s];
mat->rows[s] = mat->rows[r];
mat->rows[r] = u;
}
}
slong
nmod_poly_mat_fflu(nmod_poly_mat_t B, nmod_poly_t den, slong * perm,
const nmod_poly_mat_t A, int rank_check)
{
nmod_poly_t t;
slong m, n, j, k, rank, r, pivot_row, pivot_col;
if (nmod_poly_mat_is_empty(A))
{
nmod_poly_one(den);
return 0;
}
nmod_poly_mat_set(B, A);
m = B->r;
n = B->c;
rank = pivot_row = pivot_col = 0;
nmod_poly_init(t, nmod_poly_mat_modulus(A));
while (pivot_row < m && pivot_col < n)
{
r = nmod_poly_mat_find_pivot_partial(B, pivot_row, m, pivot_col);
if (r == -1)
{
if (rank_check)
{
nmod_poly_zero(den);
rank = 0;
break;
}
pivot_col++;
continue;
}
else if (r != pivot_row)
nmod_poly_mat_swap_rows(B, perm, pivot_row, r);
rank++;
for (j = pivot_row + 1; j < m; j++)
{
for (k = pivot_col + 1; k < n; k++)
{
nmod_poly_mul(E(j, k), E(j, k), E(pivot_row, pivot_col));
nmod_poly_mul(t, E(j, pivot_col), E(pivot_row, k));
nmod_poly_sub(E(j, k), E(j, k), t);
if (pivot_row > 0)
nmod_poly_div(E(j, k), E(j, k), den);
}
}
nmod_poly_set(den, E(pivot_row, pivot_col));
pivot_row++;
pivot_col++;
}
nmod_poly_clear(t);
return rank;
}