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/*
Copyright (C) 2011, 2026 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.h"
#include "nmod_vec.h"
#include "nmod_mat.h"
slong
nmod_mat_lu_with_pivots(slong * P, slong * pivots_nonpivots, nmod_mat_t A)
{
slong i, j, k, n, rank;
slong * pivots;
slong * nonpivots;
n = A->c;
rank = nmod_mat_lu(P, A, 0);
if (rank == 0 || rank == n)
{
for (i = 0; i < n; i++)
pivots_nonpivots[i] = i;
return rank;
}
pivots = pivots_nonpivots;
nonpivots = pivots_nonpivots + rank;
for (i = j = k = 0; i < rank; i++)
{
while (nmod_mat_entry(A, i, j) == UWORD(0))
{
nonpivots[k] = j;
k++;
j++;
}
pivots[i] = j;
j++;
}
while (k < n - rank)
{
nonpivots[k] = j;
k++;
j++;
}
return rank;
}