111 lines
2.7 KiB
C
111 lines
2.7 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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******************************************************************************/
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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 __inline__ int
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nmod_mat_pivot(nmod_mat_t A, slong * P, slong start_row, slong col)
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{
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slong j, t;
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mp_ptr u;
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if (nmod_mat_entry(A, start_row, col) != 0)
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return 1;
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for (j = start_row + 1; j < A->r; j++)
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{
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if (nmod_mat_entry(A, j, col) != 0)
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{
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u = A->rows[j];
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A->rows[j] = A->rows[start_row];
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A->rows[start_row] = u;
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t = P[j];
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P[j] = P[start_row];
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P[start_row] = t;
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return -1;
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}
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}
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return 0;
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}
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slong
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nmod_mat_lu_classical(slong * P, nmod_mat_t A, int rank_check)
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{
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mp_limb_t d, e, **a;
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nmod_t mod;
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slong i, m, n, rank, length, row, col;
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m = A->r;
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n = A->c;
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a = A->rows;
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mod = A->mod;
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rank = row = col = 0;
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for (i = 0; i < m; i++)
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P[i] = i;
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while (row < m && col < n)
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{
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if (nmod_mat_pivot(A, P, row, col) == 0)
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{
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if (rank_check)
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return 0;
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col++;
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continue;
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}
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rank++;
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d = a[row][col];
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d = n_invmod(d, mod.n);
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length = n - col - 1;
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for (i = row + 1; i < m; i++)
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{
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e = n_mulmod2_preinv(a[i][col], d, mod.n, mod.ninv);
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if (length != 0)
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_nmod_vec_scalar_addmul_nmod(a[i] + col + 1,
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a[row] + col + 1, length, nmod_neg(e, mod), mod);
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a[i][col] = 0;
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a[i][rank - 1] = e;
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}
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row++;
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col++;
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}
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return rank;
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}
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