pqc/external/flint-2.4.3/nmod_mat/lu_recursive.c

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2014-05-18 22:03:37 +00:00
/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Fredrik Johansson
Loosely based on the recursive PLS implementation in M4RI,
Copyright (C) 2008 Clement Pernet.
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include "flint.h"
#include "ulong_extras.h"
#include "nmod_vec.h"
#include "nmod_mat.h"
static void
_apply_permutation(slong * AP, nmod_mat_t A, slong * P,
slong n, slong offset)
{
if (n != 0)
{
mp_ptr * Atmp;
slong * APtmp;
slong i;
Atmp = flint_malloc(sizeof(mp_ptr) * n);
APtmp = flint_malloc(sizeof(slong) * n);
for (i = 0; i < n; i++) Atmp[i] = A->rows[P[i] + offset];
for (i = 0; i < n; i++) A->rows[i + offset] = Atmp[i];
for (i = 0; i < n; i++) APtmp[i] = AP[P[i] + offset];
for (i = 0; i < n; i++) AP[i + offset] = APtmp[i];
flint_free(Atmp);
flint_free(APtmp);
}
}
slong
nmod_mat_lu_recursive(slong * P, nmod_mat_t A, int rank_check)
{
slong i, j, m, n, r1, r2, n1;
nmod_mat_t A0, A1, A00, A01, A10, A11;
slong * P1;
m = A->r;
n = A->c;
if (m < NMOD_MAT_LU_RECURSIVE_CUTOFF || n < NMOD_MAT_LU_RECURSIVE_CUTOFF)
{
r1 = nmod_mat_lu_classical(P, A, rank_check);
return r1;
}
n1 = n / 2;
for (i = 0; i < m; i++)
P[i] = i;
P1 = flint_malloc(sizeof(slong) * m);
nmod_mat_window_init(A0, A, 0, 0, m, n1);
nmod_mat_window_init(A1, A, 0, n1, m, n);
r1 = nmod_mat_lu(P1, A0, rank_check);
if (rank_check && (r1 != n1))
{
flint_free(P1);
nmod_mat_window_clear(A0);
nmod_mat_window_clear(A1);
return 0;
}
if (r1 != 0)
{
_apply_permutation(P, A, P1, m, 0);
}
nmod_mat_window_init(A00, A, 0, 0, r1, r1);
nmod_mat_window_init(A10, A, r1, 0, m, r1);
nmod_mat_window_init(A01, A, 0, n1, r1, n);
nmod_mat_window_init(A11, A, r1, n1, m, n);
if (r1 != 0)
{
nmod_mat_solve_tril(A01, A00, A01, 1);
nmod_mat_submul(A11, A11, A10, A01);
}
r2 = nmod_mat_lu(P1, A11, rank_check);
if (rank_check && (r1 + r2 < FLINT_MIN(m, n)))
{
r1 = r2 = 0;
}
else
{
_apply_permutation(P, A, P1, m - r1, r1);
/* Compress L */
if (r1 != n1)
{
for (i = 0; i < m - r1; i++)
{
mp_ptr row = A->rows[r1 + i];
for (j = 0; j < FLINT_MIN(i, r2); j++)
{
row[r1 + j] = row[n1 + j];
row[n1 + j] = 0;
}
}
}
}
flint_free(P1);
nmod_mat_window_clear(A00);
nmod_mat_window_clear(A01);
nmod_mat_window_clear(A10);
nmod_mat_window_clear(A11);
nmod_mat_window_clear(A0);
nmod_mat_window_clear(A1);
return r1 + r2;
}