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

87 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 "fmpq_mat.h"
slong
fmpq_mat_rref_classical(fmpq_mat_t B, const fmpq_mat_t A)
{
slong m, n, i, j, pivot_row, pivot_col, rank;
m = A->r;
n = A->c;
if (m == 0 || n == 0)
return 0;
if (A != B)
fmpq_mat_set(B, A);
rank = 0;
pivot_row = 0;
pivot_col = 0;
while (pivot_row < m && pivot_col < n)
{
if (!fmpq_mat_pivot(NULL, B, pivot_row, pivot_col))
{
pivot_col++;
continue;
}
rank++;
/* Scale row to have 1 as leading entry */
for (j = pivot_col + 1; j < n; j++)
{
fmpq_div(fmpq_mat_entry(B, pivot_row, j),
fmpq_mat_entry(B, pivot_row, j),
fmpq_mat_entry(B, pivot_row, pivot_col));
}
/* Eliminate rows above and below */
for (i = 0; i < m; i++)
{
if (i == pivot_row ||
fmpq_is_zero(fmpq_mat_entry(B, i, pivot_col)))
continue;
for (j = pivot_col + 1; j < n; j++)
fmpq_submul(fmpq_mat_entry(B, i, j),
fmpq_mat_entry(B, pivot_row, j),
fmpq_mat_entry(B, i, pivot_col));
}
/* Clear pivot column */
for (i = 0; i < m; i++)
fmpq_set_si(fmpq_mat_entry(B, i, pivot_col), i == pivot_row, 1);
pivot_row++;
pivot_col++;
}
return rank;
}