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/*
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_adjugate_charpoly(gr_mat_t adj, gr_ptr det, const gr_mat_t A, gr_ctx_t ctx)
{
int status = GR_SUCCESS;
gr_ptr pol;
slong n;
slong sz = ctx->sizeof_elem;
n = gr_mat_nrows(A, ctx);
if (n != gr_mat_ncols(A, ctx))
return GR_DOMAIN;
if (n == 0)
{
return gr_one(det, ctx);
}
else
{
GR_TMP_INIT_VEC(pol, n + 1, ctx);
status |= _gr_mat_charpoly(pol, A, ctx);
if (n % 2)
status |= gr_neg(det, pol, ctx);
else
gr_swap(det, pol, ctx);
/* todo: verify that _gr_mat_gr_poly_evaluate supports aliasing */
status |= _gr_mat_gr_poly_evaluate(adj, GR_ENTRY(pol, 1, sz), n, A, ctx);
if (n % 2 == 0)
status |= gr_mat_neg(adj, adj, ctx);
GR_TMP_CLEAR_VEC(pol, n + 1, ctx);
}
return status;
}