mirror of
https://github.com/vale981/arb
synced 2025-03-06 01:41:39 -05:00
88 lines
2.5 KiB
C
88 lines
2.5 KiB
C
/*=============================================================================
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This file is part of ARB.
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ARB 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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ARB 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 ARB; 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) 2012 Fredrik Johansson
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******************************************************************************/
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#include "arb_mat.h"
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void
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arb_mat_solve_lu_precomp(arb_mat_t X, const slong * perm,
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const arb_mat_t A, const arb_mat_t B, slong prec)
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{
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slong i, j, c, n, m;
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n = arb_mat_nrows(X);
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m = arb_mat_ncols(X);
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if (X == B)
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{
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arb_ptr tmp = flint_malloc(sizeof(arb_struct) * n);
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for (c = 0; c < m; c++)
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{
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for (i = 0; i < n; i++)
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tmp[i] = B->rows[perm[i]][c];
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for (i = 0; i < n; i++)
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X->rows[i][c] = tmp[i];
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}
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flint_free(tmp);
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}
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else
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{
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for (c = 0; c < m; c++)
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{
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for (i = 0; i < n; i++)
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{
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arb_set(arb_mat_entry(X, i, c),
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arb_mat_entry(B, perm[i], c));
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}
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}
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}
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for (c = 0; c < m; c++)
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{
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/* solve Ly = b */
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for (i = 1; i < n; i++)
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{
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for (j = 0; j < i; j++)
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{
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arb_submul(arb_mat_entry(X, i, c),
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arb_mat_entry(A, i, j), arb_mat_entry(X, j, c), prec);
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}
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}
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/* solve Ux = y */
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for (i = n - 1; i >= 0; i--)
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{
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for (j = i + 1; j < n; j++)
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{
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arb_submul(arb_mat_entry(X, i, c),
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arb_mat_entry(A, i, j), arb_mat_entry(X, j, c), prec);
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}
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arb_div(arb_mat_entry(X, i, c), arb_mat_entry(X, i, c),
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arb_mat_entry(A, i, i), prec);
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}
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}
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}
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