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

93 lines
2.5 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 "fmpz_mat.h"
#include "perm.h"
#define E(j,k) fmpz_mat_entry(B,j,k)
slong
fmpz_mat_fflu(fmpz_mat_t B, fmpz_t den, slong * perm,
const fmpz_mat_t A, int rank_check)
{
fmpz_t t;
slong m, n, j, k, rank, r, pivot_row, pivot_col;
if (fmpz_mat_is_empty(A))
{
fmpz_one(den);
return 0;
}
fmpz_mat_set(B, A);
m = B->r;
n = B->c;
rank = pivot_row = pivot_col = 0;
fmpz_init(t);
while (pivot_row < m && pivot_col < n)
{
r = fmpz_mat_find_pivot_any(B, pivot_row, m, pivot_col);
if (r == -1)
{
if (rank_check)
{
fmpz_zero(den);
rank = 0;
break;
}
pivot_col++;
continue;
}
else if (r != pivot_row)
fmpz_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++)
{
/* todo: use submul */
fmpz_mul(E(j, k), E(j, k), E(pivot_row, pivot_col));
fmpz_mul(t, E(j, pivot_col), E(pivot_row, k));
fmpz_sub(E(j, k), E(j, k), t);
if (pivot_row > 0)
fmpz_divexact(E(j, k), E(j, k), den);
}
}
fmpz_set(den, E(pivot_row, pivot_col));
pivot_row++;
pivot_col++;
}
fmpz_clear(t);
return rank;
}