99 lines
2.6 KiB
C
99 lines
2.6 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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Copyright (C) 2012 Lina Kulakova
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******************************************************************************/
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#include "fmpz_mat.h"
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#define E(j,k) fmpz_mat_entry(A,j,k)
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slong
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fmpz_mat_rref_mod(slong * perm, fmpz_mat_t A, const fmpz_t p)
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{
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fmpz_t t, inv;
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slong m, n, j, k, rank, r, pivot_row, pivot_col;
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if (fmpz_mat_is_empty(A))
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{
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return 0;
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}
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m = A->r;
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n = A->c;
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rank = pivot_row = pivot_col = 0;
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fmpz_init(t);
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fmpz_init(inv);
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while (pivot_row < m && pivot_col < n)
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{
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r = fmpz_mat_find_pivot_any(A, pivot_row, m, pivot_col);
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if (r == -1)
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{
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pivot_col++;
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continue;
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}
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else if (r != pivot_row)
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{
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fmpz_mat_swap_rows(A, perm, pivot_row, r);
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}
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rank++;
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fmpz_invmod(inv, E(pivot_row, pivot_col), p);
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/* pivot row */
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for (k = pivot_col + 1; k < n; k++)
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{
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fmpz_mul(E(pivot_row, k), E(pivot_row, k), inv);
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fmpz_mod(E(pivot_row, k), E(pivot_row, k), p);
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}
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fmpz_one(E(pivot_row, pivot_col));
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/* other rows */
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for (j = 0; j < m; j++)
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{
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if (j == pivot_row)
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continue;
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for (k = pivot_col + 1; k < n; k++)
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{
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fmpz_mul(t, E(j, pivot_col), E(pivot_row, k));
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fmpz_sub(E(j, k), E(j, k), t);
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fmpz_mod(E(j, k), E(j, k), p);
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}
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fmpz_zero(E(j, pivot_col));
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}
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pivot_row++;
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pivot_col++;
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}
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fmpz_clear(inv);
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fmpz_clear(t);
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return rank;
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}
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