98 lines
2.8 KiB
C
98 lines
2.8 KiB
C
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/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2011 Fredrik Johansson
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******************************************************************************/
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#include "fmpz_mat.h"
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#define XX(ii,jj) fmpz_mat_entry(X,(ii),(jj))
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#define BB(ii,jj) fmpz_mat_entry(B,(ii),(jj))
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#define LU(ii,jj) fmpz_mat_entry(FFLU,(ii),(jj))
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void
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fmpz_mat_set_perm(fmpz_mat_t X, const slong * perm, const fmpz_mat_t B)
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{
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if (X == B)
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{
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/* Not implemented */
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abort();
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}
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else
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{
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slong i, j;
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if (perm == NULL)
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abort();
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for (i = 0; i < fmpz_mat_nrows(B); i++)
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for (j = 0; j < fmpz_mat_ncols(B); j++)
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fmpz_set(fmpz_mat_entry(X, i, j),
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fmpz_mat_entry(B, perm[i], j));
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}
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}
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void
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fmpz_mat_solve_fflu_precomp(fmpz_mat_t X,
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const slong * perm,
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const fmpz_mat_t FFLU, const fmpz_mat_t B)
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{
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fmpz_t T;
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slong i, j, k, m, n;
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n = X->r;
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m = X->c;
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fmpz_init(T);
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fmpz_mat_set_perm(X, perm, B);
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for (k = 0; k < m; k++)
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{
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/* Fraction-free forward substitution */
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for (i = 0; i < n - 1; i++)
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{
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for (j = i + 1; j < n; j++)
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{
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fmpz_mul(XX(j, k), XX(j, k), LU(i, i));
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fmpz_mul(T, LU(j, i), XX(i, k));
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fmpz_sub(XX(j, k), XX(j, k), T);
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if (i > 0)
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fmpz_divexact(XX(j, k), XX(j, k), LU(i-1, i-1));
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}
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}
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/* Fraction-free back substitution */
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for (i = n - 2; i >= 0; i--)
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{
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fmpz_mul(XX(i, k), XX(i, k), LU(n-1, n-1));
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for (j = i + 1; j < n; j++)
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{
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fmpz_mul(T, XX(j, k), LU(i, j));
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fmpz_sub(XX(i, k), XX(i, k), T);
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}
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fmpz_divexact(XX(i, k), XX(i, k), LU(i, i));
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}
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}
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fmpz_clear(T);
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}
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