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/*
Copyright (C) 2011 Fredrik Johansson
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#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;
}