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/*
Copyright (C) 2015 William Hart
Copyright (C) 2022 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 "gr.h"
#include "gr_mat.h"
int gr_mat_reduce_row(slong * column, gr_mat_t A, slong * P, slong * L, slong m, gr_ctx_t ctx)
{
int status = GR_SUCCESS;
slong n = A->c, i, j, r;
gr_ptr h;
truth_t is_zero;
slong sz = ctx->sizeof_elem;
*column = -1;
GR_TMP_INIT(h, ctx);
for (i = 0; i < n; i++)
{
is_zero = gr_is_zero(GR_MAT_ENTRY(A, m, i, sz), ctx);
if (is_zero == T_UNKNOWN)
{
status |= GR_UNABLE;
break;
}
if (is_zero == T_FALSE)
{
r = P[i];
if (r != -1)
{
for (j = i + 1; j < L[r]; j++)
{
status |= gr_mul(h, GR_MAT_ENTRY(A, r, j, sz), GR_MAT_ENTRY(A, m, i, sz), ctx);
status |= gr_sub(GR_MAT_ENTRY(A, m, j, sz), GR_MAT_ENTRY(A, m, j, sz), h, ctx);
}
status |= gr_zero(GR_MAT_ENTRY(A, m, i, sz), ctx);
}
else
{
status |= gr_inv(h, GR_MAT_ENTRY(A, m, i, sz), ctx);
status |= gr_one(GR_MAT_ENTRY(A, m, i, sz), ctx);
for (j = i + 1; j < L[m]; j++)
status |= gr_mul(GR_MAT_ENTRY(A, m, j, sz), GR_MAT_ENTRY(A, m, j, sz), h, ctx);
P[i] = m;
*column = i;
break;
}
}
}
GR_TMP_CLEAR(h, ctx);
return status;
}