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On-the-fly filtering for KNN search #1

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39 changes: 29 additions & 10 deletions hnswlib/hnswalg.h
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Original file line number Diff line number Diff line change
Expand Up @@ -312,17 +312,19 @@ class HierarchicalNSW : public AlgorithmInterface<dist_t> {

template <bool has_deletions, bool collect_metrics = false>
std::priority_queue<std::pair<dist_t, tableint>, std::vector<std::pair<dist_t, tableint>>, CompareByFirst>
searchBaseLayerST(tableint ep_id, const void *data_point, size_t ef, BaseFilterFunctor* isIdAllowed = nullptr) const {
searchBaseLayerST(tableint ep_id, const void *data_point, size_t ef, BaseFilterFunctor* isIdAllowed = nullptr, size_t k = 0) const {
VisitedList *vl = visited_list_pool_->getFreeVisitedList();
vl_type *visited_array = vl->mass;
vl_type visited_array_tag = vl->curV;
const bool use_filter = isIdAllowed && k > 0;

std::priority_queue<std::pair<dist_t, tableint>, std::vector<std::pair<dist_t, tableint>>, CompareByFirst> top_candidates;
std::priority_queue<std::pair<dist_t, tableint>, std::vector<std::pair<dist_t, tableint>>, CompareByFirst> candidate_set;

dist_t lowerBound;
if ((!has_deletions || !isMarkedDeleted(ep_id)) && ((!isIdAllowed) || (*isIdAllowed)(getExternalLabel(ep_id)))) {
dist_t dist = fstdistfunc_(data_point, getDataByInternalId(ep_id), (labeltype)-1, getExternalLabel(ep_id), dist_func_param_);
labeltype ep_label = getExternalLabel(ep_id);
if ((!has_deletions || !isMarkedDeleted(ep_id)) && ((!isIdAllowed) || (*isIdAllowed)(ep_label))) {
dist_t dist = fstdistfunc_(data_point, getDataByInternalId(ep_id), (labeltype)-1, ep_label, dist_func_param_);
lowerBound = dist;
top_candidates.emplace(dist, ep_id);
candidate_set.emplace(-dist, ep_id);
Expand All @@ -336,8 +338,19 @@ class HierarchicalNSW : public AlgorithmInterface<dist_t> {
while (!candidate_set.empty()) {
std::pair<dist_t, tableint> current_node_pair = candidate_set.top();

if ((-current_node_pair.first) > lowerBound &&
(top_candidates.size() == ef || (!isIdAllowed && !has_deletions))) {
bool should_break = false;
if (use_filter) {
// Continue until we have k filtered candidates
if (top_candidates.size() >= k && (-current_node_pair.first) > lowerBound) {
should_break = true;
}
} else {
if ((-current_node_pair.first) > lowerBound &&
(top_candidates.size() == ef || (!isIdAllowed && !has_deletions))) {
should_break = true;
}
}
if (should_break) {
break;
}
candidate_set.pop();
Expand Down Expand Up @@ -370,18 +383,23 @@ class HierarchicalNSW : public AlgorithmInterface<dist_t> {
visited_array[candidate_id] = visited_array_tag;

char *currObj1 = (getDataByInternalId(candidate_id));
dist_t dist = fstdistfunc_(data_point, currObj1, (labeltype)-1, getExternalLabel(candidate_id), dist_func_param_);
labeltype cand_label = getExternalLabel(candidate_id);
dist_t dist = fstdistfunc_(data_point, currObj1, (labeltype)-1, cand_label, dist_func_param_);

if (top_candidates.size() < ef || lowerBound > dist) {
bool should_explore = (use_filter && top_candidates.size() < k) ||
(top_candidates.size() < ef || lowerBound > dist);
if (should_explore) {
candidate_set.emplace(-dist, candidate_id);
#ifdef USE_SSE
_mm_prefetch(data_level0_memory_ + candidate_set.top().second * size_data_per_element_ +
offsetLevel0_, ///////////
_MM_HINT_T0); ////////////////////////
#endif

if ((!has_deletions || !isMarkedDeleted(candidate_id)) && ((!isIdAllowed) || (*isIdAllowed)(getExternalLabel(candidate_id))))
bool is_filtered = (!has_deletions || !isMarkedDeleted(candidate_id)) && ((!isIdAllowed) || (*isIdAllowed)(cand_label));
if (is_filtered) {
top_candidates.emplace(dist, candidate_id);
}

if (top_candidates.size() > ef)
top_candidates.pop();
Expand Down Expand Up @@ -1367,13 +1385,14 @@ class HierarchicalNSW : public AlgorithmInterface<dist_t> {
size_t searchEf = std::max(ef_, k);
if ( ef )
searchEf = std::max(searchEf, *ef);

std::priority_queue<std::pair<dist_t, tableint>, std::vector<std::pair<dist_t, tableint>>, CompareByFirst> top_candidates;
if (num_deleted_) {
top_candidates = searchBaseLayerST<true, true>(
currObj, query_data, searchEf, isIdAllowed);
currObj, query_data, searchEf, isIdAllowed, isIdAllowed ? k : 0);
} else {
top_candidates = searchBaseLayerST<false, true>(
currObj, query_data, searchEf, isIdAllowed);
currObj, query_data, searchEf, isIdAllowed, isIdAllowed ? k : 0);
}

while (top_candidates.size() > k) {
Expand Down