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/******************************************************************************
*
* M4RI: Linear Algebra over GF(2)
*
* Copyright (C) 2007 Gregory Bard <gregory.bard@ieee.org>
* Copyright (C) 2007 Martin Albrecht <malb@informatik.uni-bremen.de>
*
* Distributed under the terms of the GNU General Public License (GPL)
* version 2 or higher.
*
* This code 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.
*
* The full text of the GPL is available at:
*
* http://www.gnu.org/licenses/
******************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "graycode.h"
#include "misc.h"
#include <stdio.h>
code **m4ri_codebook = NULL;
int m4ri_gray_code(int number, int length) {
int lastbit = 0;
int res = 0;
for (int i = length - 1; i >= 0; --i) {
int bit = number & (1 << i);
res |= (lastbit >> 1) ^ bit;
lastbit = bit;
}
return res;
}
void m4ri_build_code(int *ord, int *inc, int l) {
for (int i = 0; i < (int)__M4RI_TWOPOW(l); ++i) { ord[i] = m4ri_gray_code(i, l); }
for (int i = l; i > 0; --i) {
for (int j = 1; j < (int)__M4RI_TWOPOW(i) + 1; ++j) {
inc[j * __M4RI_TWOPOW(l - i) - 1] = l - i;
}
}
}
void m4ri_build_all_codes() {
if (m4ri_codebook) { return; }
m4ri_codebook = (code **)m4ri_mm_calloc(__M4RI_MAXKAY + 1, sizeof(code *));
for (int k = 1; k < __M4RI_MAXKAY + 1; ++k) {
m4ri_codebook[k] = (code *)m4ri_mm_calloc(1, sizeof(code));
m4ri_codebook[k]->ord = (int *)m4ri_mm_calloc(__M4RI_TWOPOW(k), sizeof(int));
m4ri_codebook[k]->inc = (int *)m4ri_mm_calloc(__M4RI_TWOPOW(k), sizeof(int));
m4ri_build_code(m4ri_codebook[k]->ord, m4ri_codebook[k]->inc, k);
}
}
void m4ri_destroy_all_codes() {
if (!m4ri_codebook) { return; }
for (int i = 1; i < __M4RI_MAXKAY + 1; ++i) {
m4ri_mm_free(m4ri_codebook[i]->inc);
m4ri_mm_free(m4ri_codebook[i]->ord);
m4ri_mm_free(m4ri_codebook[i]);
}
m4ri_mm_free(m4ri_codebook);
m4ri_codebook = NULL;
}
int m4ri_opt_k(int a, int b, int c) {
int n = MIN(a, b);
int res = MIN(__M4RI_MAXKAY, MAX(1, (int)(0.75 * (1 + log2_floor(n)))));
return res;
}
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