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Avoid extra Leiden mapping copies #30

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Merged
adsharma merged 1 commit into from
May 1, 2026
Merged

Avoid extra Leiden mapping copies #30

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14 changes: 6 additions & 8 deletions networkit/cpp/community/ParallelLeidenView.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -261,16 +261,15 @@ void ParallelLeidenView::run() {
ParallelPartitionCoarseningView ppcView(*G, originalRefined);
ppcView.run();
auto newCoarsenedView = ppcView.getCoarsenedGraphView();
auto map = ppcView.getFineToCoarseNodeMapping();
const auto &map = ppcView.getFineToCoarseNodeMapping();
const auto &oldNodeMapping = currentCoarsenedView->getNodeMapping();

// Create new partition for the new coarsened view
Partition p(newCoarsenedView->numberOfNodes());
p.setUpperBound(result.upperBound());

// Map communities through the chain of coarsenings BEFORE moving map
// Capture map by value and other refs explicitly
G->parallelForNodes([map = map, &p, this, &oldNodeMapping](node originalNode) {
G->parallelForNodes([&map, &p, this, &oldNodeMapping](node originalNode) {
node newCoarseNode = map[originalNode];
// Find what community this original node belonged to
node oldCoarseNode = oldNodeMapping[originalNode];
Expand All @@ -279,7 +278,7 @@ void ParallelLeidenView::run() {

// Since ppcView is always built from *G, map already represents
// original -> current-coarse directly. No chain composition needed.
composedMapping = std::move(map);
composedMapping = map;

result = std::move(p);
currentCoarsenedView = newCoarsenedView;
Expand All @@ -289,16 +288,15 @@ void ParallelLeidenView::run() {
ParallelPartitionCoarseningView ppcView(*currentGraph, refined);
ppcView.run();
auto newCoarsenedView = ppcView.getCoarsenedGraphView();
auto map = ppcView.getFineToCoarseNodeMapping();
const auto &map = ppcView.getFineToCoarseNodeMapping();

// Maintain Partition, add every coarse Node to the community its fine Nodes were in
Partition p(newCoarsenedView->numberOfNodes());
p.setUpperBound(result.upperBound());
currentGraph->parallelForNodes(
[map = map, &p, this](node u) { p[map[u]] = result[u]; });
currentGraph->parallelForNodes([&map, &p, this](node u) { p[map[u]] = result[u]; });

// ppcView is built from *G so map is already original -> coarse; just store it.
composedMapping = std::move(map);
composedMapping = map;
result = std::move(p);

currentCoarsenedView = newCoarsenedView;
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