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/*
Copyright (C) 2024 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 "fmpz_mod.h"
#include "fmpz_mod_mat.h"
#include "gr.h"
#include "gr_mat.h"
void fmpz_mod_mat_det(fmpz_t res, const fmpz_mod_mat_t mat, const fmpz_mod_ctx_t ctx)
{
gr_ctx_t gr_ctx;
slong n = mat->r;
if (!fmpz_mod_mat_is_square(mat, ctx))
{
flint_throw(FLINT_ERROR, "Exception (fmpz_mod_mat_charpoly_berkowitz). Non-square matrix.\n");
}
_gr_ctx_init_fmpz_mod_from_ref(gr_ctx, ctx);
if (n <= 4)
{
GR_MUST_SUCCEED(gr_mat_det_cofactor(res, (const gr_mat_struct *) mat, gr_ctx));
}
else
{
if (gr_mat_det_lu(res, (const gr_mat_struct *) mat, gr_ctx) != GR_SUCCESS)
{
/* Fall back on division-free algorithm if we encountered an impossible inverse */
/* Could try something else here: faddeev_bsgs (O(n^3.5)) or Howell form. */
GR_MUST_SUCCEED(gr_mat_det_berkowitz(res, (const gr_mat_struct *) mat, gr_ctx));
}
}
}