113 lines
4.4 KiB
C
113 lines
4.4 KiB
C
#include "bf_decoding.h"
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#include "dfr_test.h"
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#include "gf2x_arith_mod_xPplusOne.h"
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#include "qc_ldpc_parameters.h"
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#include <string.h>
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/* Tests if the current code attains the desired DFR. If that is the case,
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* computes the threshold for the second iteration of the decoder and returns this values
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* (max DV * M), on failure it returns 255 >> DV * M */
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uint8_t PQCLEAN_LEDAKEMLT52_LEAKTIME_DFR_test(POSITION_T LSparse[N0][DV * M]) {
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POSITION_T LSparse_loc[N0][DV * M];
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POSITION_T rotated_column[DV * M];
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/* Gamma matrix: an N0 x N0 block circulant matrix with block size p
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* gamma[a][b][c] stores the intersection of the first column of the a-th
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* block of L with the c-th column of the b-th block of L.
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* Gamma computation can be accelerated employing symmetry and QC properties */
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unsigned int gamma[N0][N0][P] = {{{0}}};
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unsigned int gammaHist[N0][DV * M + 1] = {{0}};
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unsigned int maxMut[N0], maxMutMinusOne[N0];
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unsigned int firstidx, secondidx, intersectionval;
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unsigned int allBlockMaxSumst, allBlockMaxSumstMinusOne;
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unsigned int toAdd, histIdx;
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/*transpose blocks of L, we need its columns */
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for (int i = 0; i < N0; i++) {
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for (int j = 0; j < DV * M; j++) {
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if (LSparse[i][j] != 0) {
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LSparse_loc[i][j] = (P - LSparse[i][j]);
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}
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}
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PQCLEAN_LEDAKEMLT52_LEAKTIME_quicksort_sparse(LSparse_loc[i]);
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}
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for (int i = 0; i < N0; i++ ) {
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for (int j = 0; j < N0; j++ ) {
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for (int k = 0; k < P; k++) {
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/* compute the rotated sparse column needed */
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for (int idxToRotate = 0; idxToRotate < (DV * M); idxToRotate++) {
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rotated_column[idxToRotate] = (LSparse_loc[j][idxToRotate] + k) % P;
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}
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PQCLEAN_LEDAKEMLT52_LEAKTIME_quicksort_sparse(rotated_column);
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/* compute the intersection amount */
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firstidx = 0, secondidx = 0;
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intersectionval = 0;
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while ( (firstidx < DV * M) && (secondidx < DV * M) ) {
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if ( LSparse_loc[i][firstidx] == rotated_column[secondidx] ) {
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intersectionval++;
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firstidx++;
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secondidx++;
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} else if ( LSparse_loc[i][firstidx] > rotated_column[secondidx] ) {
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secondidx++;
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} else { /*if ( LSparse_loc[i][firstidx] < rotated_column[secondidx] ) */
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firstidx++;
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}
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}
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gamma[i][j][k] = intersectionval;
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}
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}
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}
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for (int i = 0; i < N0; i++ ) {
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for (int j = 0; j < N0; j++ ) {
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gamma[i][j][0] = 0;
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}
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}
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/* build histogram of values in gamma */
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for (int i = 0; i < N0; i++ ) {
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for (int j = 0; j < N0; j++ ) {
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for (int k = 0; k < P; k++) {
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gammaHist[i][gamma[i][j][k]]++;
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}
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}
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}
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for (int gammaBlockRowIdx = 0; gammaBlockRowIdx < N0; gammaBlockRowIdx++) {
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toAdd = T_BAR - 1;
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maxMutMinusOne[gammaBlockRowIdx] = 0;
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histIdx = DV * M;
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while ( (histIdx > 0) && (toAdd > 0)) {
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if (gammaHist[gammaBlockRowIdx][histIdx] > toAdd ) {
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maxMutMinusOne[gammaBlockRowIdx] += histIdx * toAdd;
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toAdd = 0;
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} else {
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maxMutMinusOne[gammaBlockRowIdx] += histIdx * gammaHist[gammaBlockRowIdx][histIdx];
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toAdd -= gammaHist[gammaBlockRowIdx][histIdx];
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histIdx--;
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}
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}
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maxMut[gammaBlockRowIdx] = histIdx + maxMutMinusOne[gammaBlockRowIdx];
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}
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/*seek max values across all gamma blocks */
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allBlockMaxSumst = maxMut[0];
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allBlockMaxSumstMinusOne = maxMutMinusOne[0];
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for (int gammaBlockRowIdx = 0; gammaBlockRowIdx < N0 ; gammaBlockRowIdx++) {
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allBlockMaxSumst = allBlockMaxSumst < maxMut[gammaBlockRowIdx] ?
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maxMut[gammaBlockRowIdx] :
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allBlockMaxSumst;
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allBlockMaxSumstMinusOne = allBlockMaxSumstMinusOne < maxMutMinusOne[gammaBlockRowIdx] ?
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maxMutMinusOne[gammaBlockRowIdx] :
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allBlockMaxSumstMinusOne;
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}
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if (DV * M > (allBlockMaxSumstMinusOne + allBlockMaxSumst)) {
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return (uint8_t) allBlockMaxSumst + 1;
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}
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return DFR_TEST_FAIL;
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}
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