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

57 lines
1.8 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"
slong
nmod_poly_mat_find_pivot_partial(const nmod_poly_mat_t mat,
slong start_row, slong end_row, slong c)
{
slong best_row, best_length, i;
best_row = start_row;
best_length = nmod_poly_length(nmod_poly_mat_entry(mat, start_row, c));
for (i = start_row + 1; i < end_row; i++)
{
slong l;
l = nmod_poly_length(nmod_poly_mat_entry(mat, i, c));
if (l != 0 && (best_length == 0 || l <= best_length))
{
best_row = i;
best_length = l;
}
}
if (best_length == 0)
return -1;
return best_row;
}