148 lines
3.8 KiB
C
148 lines
3.8 KiB
C
/*=============================================================================
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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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Loosely based on the recursive PLS implementation in M4RI,
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Copyright (C) 2008 Clement Pernet.
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******************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include "flint.h"
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#include "ulong_extras.h"
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#include "nmod_vec.h"
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#include "nmod_mat.h"
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static void
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_apply_permutation(slong * AP, nmod_mat_t A, slong * P,
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slong n, slong offset)
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{
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if (n != 0)
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{
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mp_ptr * Atmp;
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slong * APtmp;
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slong i;
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Atmp = flint_malloc(sizeof(mp_ptr) * n);
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APtmp = flint_malloc(sizeof(slong) * n);
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for (i = 0; i < n; i++) Atmp[i] = A->rows[P[i] + offset];
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for (i = 0; i < n; i++) A->rows[i + offset] = Atmp[i];
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for (i = 0; i < n; i++) APtmp[i] = AP[P[i] + offset];
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for (i = 0; i < n; i++) AP[i + offset] = APtmp[i];
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flint_free(Atmp);
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flint_free(APtmp);
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}
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}
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slong
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nmod_mat_lu_recursive(slong * P, nmod_mat_t A, int rank_check)
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{
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slong i, j, m, n, r1, r2, n1;
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nmod_mat_t A0, A1, A00, A01, A10, A11;
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slong * P1;
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m = A->r;
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n = A->c;
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if (m < NMOD_MAT_LU_RECURSIVE_CUTOFF || n < NMOD_MAT_LU_RECURSIVE_CUTOFF)
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{
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r1 = nmod_mat_lu_classical(P, A, rank_check);
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return r1;
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}
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n1 = n / 2;
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for (i = 0; i < m; i++)
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P[i] = i;
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P1 = flint_malloc(sizeof(slong) * m);
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nmod_mat_window_init(A0, A, 0, 0, m, n1);
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nmod_mat_window_init(A1, A, 0, n1, m, n);
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r1 = nmod_mat_lu(P1, A0, rank_check);
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if (rank_check && (r1 != n1))
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{
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flint_free(P1);
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nmod_mat_window_clear(A0);
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nmod_mat_window_clear(A1);
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return 0;
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}
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if (r1 != 0)
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{
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_apply_permutation(P, A, P1, m, 0);
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}
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nmod_mat_window_init(A00, A, 0, 0, r1, r1);
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nmod_mat_window_init(A10, A, r1, 0, m, r1);
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nmod_mat_window_init(A01, A, 0, n1, r1, n);
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nmod_mat_window_init(A11, A, r1, n1, m, n);
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if (r1 != 0)
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{
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nmod_mat_solve_tril(A01, A00, A01, 1);
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nmod_mat_submul(A11, A11, A10, A01);
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}
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r2 = nmod_mat_lu(P1, A11, rank_check);
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if (rank_check && (r1 + r2 < FLINT_MIN(m, n)))
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{
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r1 = r2 = 0;
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}
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else
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{
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_apply_permutation(P, A, P1, m - r1, r1);
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/* Compress L */
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if (r1 != n1)
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{
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for (i = 0; i < m - r1; i++)
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{
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mp_ptr row = A->rows[r1 + i];
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for (j = 0; j < FLINT_MIN(i, r2); j++)
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{
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row[r1 + j] = row[n1 + j];
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row[n1 + j] = 0;
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}
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}
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}
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}
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flint_free(P1);
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nmod_mat_window_clear(A00);
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nmod_mat_window_clear(A01);
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nmod_mat_window_clear(A10);
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nmod_mat_window_clear(A11);
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nmod_mat_window_clear(A0);
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nmod_mat_window_clear(A1);
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return r1 + r2;
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}
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