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/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2010 Fredrik Johansson
******************************************************************************/
#include <stdlib.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
#include "fmpz_poly_mat.h"
#include "perm.h"
#define XX(ii,jj) fmpz_poly_mat_entry(X,(ii),(jj))
#define BB(ii,jj) fmpz_poly_mat_entry(B,(ii),(jj))
#define LU(ii,jj) fmpz_poly_mat_entry(FFLU,(ii),(jj))
void
fmpz_poly_mat_set_perm(fmpz_poly_mat_t X, const slong * perm,
const fmpz_poly_mat_t B)
{
if (X == B)
{
/* Not implemented */
abort();
}
else
{
slong i, j;
if (perm == NULL)
abort();
for (i = 0; i < fmpz_poly_mat_nrows(B); i++)
for (j = 0; j < fmpz_poly_mat_ncols(B); j++)
fmpz_poly_set(fmpz_poly_mat_entry(X, i, j),
fmpz_poly_mat_entry(B, perm[i], j));
}
}
void
fmpz_poly_mat_solve_fflu_precomp(fmpz_poly_mat_t X,
const slong * perm,
const fmpz_poly_mat_t FFLU, const fmpz_poly_mat_t B)
{
fmpz_poly_t T;
slong i, j, k, m, n;
n = X->r;
m = X->c;
fmpz_poly_init(T);
fmpz_poly_mat_set_perm(X, perm, B);
for (k = 0; k < m; k++)
{
/* Fraction-free forward substitution */
for (i = 0; i < n - 1; i++)
{
for (j = i + 1; j < n; j++)
{
fmpz_poly_mul(XX(j, k), XX(j, k), LU(i, i));
fmpz_poly_mul(T, LU(j, i), XX(i, k));
fmpz_poly_sub(XX(j, k), XX(j, k), T);
if (i > 0)
fmpz_poly_div(XX(j, k), XX(j, k), LU(i-1, i-1));
}
}
/* Fraction-free back substitution */
for (i = n - 2; i >= 0; i--)
{
fmpz_poly_mul(XX(i, k), XX(i, k), LU(n-1, n-1));
for (j = i + 1; j < n; j++)
{
fmpz_poly_mul(T, XX(j, k), LU(i, j));
fmpz_poly_sub(XX(i, k), XX(i, k), T);
}
fmpz_poly_div(XX(i, k), XX(i, k), LU(i, i));
}
}
fmpz_poly_clear(T);
}
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