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Osd cs weight one fix #38

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Osd cs weight one fix #38

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a756607
If combination sweep search is used together with osd_order>0, try on…
lucasberent Apr 26, 2024
0ddf1ea
code format, remove commented out code
lucasberent Apr 26, 2024
3dc4ac2
add documentation
lucasberent Apr 28, 2024
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153 changes: 70 additions & 83 deletions src_cpp/osd.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,46 +4,45 @@
#include <vector>
#include <memory>
#include <iterator>
#include <cmath>
#include <cmath>
#include <limits>

#include "bp.hpp"
#include "sort.hpp"
#include "util.hpp"
#include "gf2sparse_linalg.hpp"

namespace ldpc::osd{
namespace ldpc::osd {


enum OsdMethod{
OSD_OFF,
OSD_0,
EXHAUSTIVE,
COMBINATION_SWEEP
};
enum OsdMethod {
OSD_OFF,
OSD_0,
EXHAUSTIVE,
COMBINATION_SWEEP
};


class OsdDecoder{
class OsdDecoder {
public:
OsdMethod osd_method;
int osd_order;
int k, bit_count, check_count;
ldpc::bp::BpSparse& pcm;
std::vector<double>& channel_probabilities;
ldpc::bp::BpSparse &pcm;
std::vector<double> &channel_probabilities;
std::vector<uint8_t> osd0_decoding;
std::vector<uint8_t> osdw_decoding;
std::vector<std::vector<uint8_t>> osd_candidate_strings;
std::vector<int> column_ordering;
ldpc::gf2sparse_linalg::RowReduce<ldpc::bp::BpEntry>* LuDecomposition;
ldpc::gf2sparse_linalg::RowReduce<ldpc::bp::BpEntry> *LuDecomposition;

OsdDecoder(
ldpc::bp::BpSparse& parity_check_matrix,
OsdMethod osd_method,
int osd_order,
std::vector<double>& channel_probs):
pcm(parity_check_matrix),
channel_probabilities(channel_probs)
{
ldpc::bp::BpSparse &parity_check_matrix,
OsdMethod osd_method,
int osd_order,
std::vector<double> &channel_probs) :
pcm(parity_check_matrix),
channel_probabilities(channel_probs) {

this->bit_count = this->pcm.n;
this->check_count = this->pcm.m;
Expand All @@ -56,44 +55,48 @@ class OsdDecoder{

}

int osd_setup(){
int osd_setup() {

this->osd_candidate_strings.clear();

if(this->osd_method == OSD_OFF) return 0;

if (this->osd_method == OSD_OFF) {
return 0;
}

this->LuDecomposition = new ldpc::gf2sparse_linalg::RowReduce<ldpc::bp::BpEntry>(this->pcm);
this->column_ordering.resize(this->pcm.n);
int osd_candidate_string_count;
this->LuDecomposition->rref(false,true);
this->LuDecomposition->rref(false, true);
this->k = this->pcm.n - this->LuDecomposition->rank;

if(this->osd_method == OSD_0 || this->osd_order==0){
if (this->osd_method == OSD_0 || this->osd_order == 0) {
return 1;
}

if(this->osd_method == EXHAUSTIVE){
osd_candidate_string_count = pow(2,this->osd_order);
for(int i=1; i<osd_candidate_string_count; i++){
this->osd_candidate_strings.push_back(ldpc::util::decimal_to_binary_reverse(i,k));
if (this->osd_method == EXHAUSTIVE) {
osd_candidate_string_count = pow(2, this->osd_order);
for (int i = 1; i < osd_candidate_string_count; i++) {
this->osd_candidate_strings.push_back(ldpc::util::decimal_to_binary_reverse(i, k));
}
}

if(this->osd_method == COMBINATION_SWEEP){
for(int i=0; i<k; i++) {
// If osd with higher order lambda>0 is used, try lambda first wt 1 solutions, otherwise all
if (this->osd_method == COMBINATION_SWEEP) {
auto lambda = this->osd_order > 0 ? this->osd_order : this->k;
for (int i = 0; i < lambda; i++) {
std::vector<uint8_t> osd_candidate;
osd_candidate.resize(k,0);
osd_candidate[i]=1;
osd_candidate.resize(k, 0);
osd_candidate[i] = 1;
this->osd_candidate_strings.push_back(osd_candidate);
}

for(int i = 0; i<this->osd_order;i++){
for(int j = 0; j<this->osd_order; j++){
if(j<=i) continue;
for (int i = 0; i < this->osd_order; i++) {
for (int j = 0; j < this->osd_order; j++) {
if (j <= i) continue;
std::vector<uint8_t> osd_candidate;
osd_candidate.resize(k,0);
osd_candidate[i]=1;
osd_candidate[j]=1;
osd_candidate.resize(k, 0);
osd_candidate[i] = 1;
osd_candidate[j] = 1;
this->osd_candidate_strings.push_back(osd_candidate);
}
}
Expand All @@ -102,93 +105,77 @@ class OsdDecoder{
return 1;
}

~OsdDecoder(){
~OsdDecoder() {
delete this->LuDecomposition;
};


std::vector<uint8_t>& decode(std::vector<uint8_t>& syndrome, std::vector<double>& log_prob_ratios) {

ldpc::sort::soft_decision_col_sort(log_prob_ratios, this->column_ordering,bit_count);
std::vector<uint8_t> &decode(std::vector<uint8_t> &syndrome, std::vector<double> &log_prob_ratios) {
ldpc::sort::soft_decision_col_sort(log_prob_ratios, this->column_ordering, bit_count);

if(this->osd_order == 0){
this->osd0_decoding = this->osdw_decoding = this->LuDecomposition->fast_solve(syndrome,this->column_ordering);
if (this->osd_order == 0) {
this->osd0_decoding = this->osdw_decoding = this->LuDecomposition->fast_solve(syndrome,
this->column_ordering);
return this->osd0_decoding;
}

//row reduce the matrix according to the new column ordering
this->LuDecomposition->rref(false,true,this->column_ordering);

this->LuDecomposition->rref(false, true, this->column_ordering);
// find the OSD0 solution
this->osd0_decoding = this->osdw_decoding = LuDecomposition->lu_solve(syndrome);

// this->osd0_decoding = this->LuDecomposition->fast_solve(syndrome,this->column_ordering);

// if(osd_order==0){
// return this->osd0_decoding;
// }

double candidate_weight, osd_min_weight;

osd_min_weight=0;
for(int i=0; i<this->pcm.n; i++){
if(this->osd0_decoding[i]==1){
osd_min_weight+=log(1/this->channel_probabilities[i]);
osd_min_weight = 0;
for (int i = 0; i < this->pcm.n; i++) {
if (this->osd0_decoding[i] == 1) {
osd_min_weight += log(1 / this->channel_probabilities[i]);
}
}

std::vector<int> non_pivot_columns;
std::vector<ldpc::gf2sparse::GF2Entry*> delete_entries;
for(int i = this->LuDecomposition->rank; i<this->pcm.n; i++){
std::vector<ldpc::gf2sparse::GF2Entry *> delete_entries;
for (int i = this->LuDecomposition->rank; i < this->pcm.n; i++) {
int col = this->LuDecomposition->cols[i];
non_pivot_columns.push_back(col);
for(auto& e: this->LuDecomposition->U.iterate_column(col)){

for (auto &e: this->LuDecomposition->U.iterate_column(col)) {
delete_entries.push_back(&e);
}
}

for (auto e: delete_entries){
for (auto e: delete_entries) {
this->LuDecomposition->U.remove(*e);
}

for(auto& candidate_string: this->osd_candidate_strings){

for (auto &candidate_string: this->osd_candidate_strings) {
auto t_syndrome = syndrome;
int col_index = 0;
for(int col: non_pivot_columns){
if(candidate_string[col_index]==1){
for(auto& e: this->pcm.iterate_column(col)){
for (int col: non_pivot_columns) {
if (candidate_string[col_index] == 1) {
for (auto &e: this->pcm.iterate_column(col)) {
t_syndrome[e.row_index] ^= 1;
}
}
col_index++;
}

auto candidate_solution = this->LuDecomposition->lu_solve(t_syndrome);
for(int i=0; i<k; i++){
candidate_solution[non_pivot_columns[i]]=candidate_string[i];
for (int i = 0; i < k; i++) {
candidate_solution[non_pivot_columns[i]] = candidate_string[i];
}
candidate_weight=0;
for(int i=0; i<this->pcm.n; i++){
if(candidate_solution[i]==1){
candidate_weight+=log(1/this->channel_probabilities[i]);
candidate_weight = 0;
for (int i = 0; i < this->pcm.n; i++) {
if (candidate_solution[i] == 1) {
candidate_weight += log(1 / this->channel_probabilities[i]);
}
}
if(candidate_weight<osd_min_weight){
if (candidate_weight < osd_min_weight) {
osd_min_weight = candidate_weight;

this->osdw_decoding = candidate_solution;

}

}

return this->osdw_decoding;

}

};
};

}//end osd namespace

Expand Down
5 changes: 4 additions & 1 deletion src_python/ldpc/bposd_decoder/_bposd_decoder.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,8 @@ cdef class BpOsdDecoder(BpDecoderBase):
osd_method : int, optional
The OSD method used. Must be one of {'OSD_0', 'OSD_E', 'OSD_CS'}.
osd_order : int, optional
The OSD order, by default 0.
The OSD order, by default 0. Note that if OSD_CS is chosen with osd_order > 0, the algorithm will consider weight
one solutions of the osd_order many most reliable bits only.

Notes
-----
Expand Down Expand Up @@ -129,6 +130,8 @@ cdef class BpOsdDecoder(BpDecoderBase):
for i in range(self.n):
out[i] = self.bpd.decoding[i]
else:
if self.osdD.osd_method == OSD_CS and self.osd_order > 0:
print(f"Using OSD_CS with osd_order={self.osd_order}, checking osd_order many weight one solutions only.")
self.osdD.decode(self._syndrome, self.bpd.log_prob_ratios)
for i in range(self.n):
out[i] = self.osdD.osdw_decoding[i]
Expand Down
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