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