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Optimize reverse neighbors for memory #590

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merged 2 commits into from
Oct 5, 2020
Merged

Optimize reverse neighbors for memory #590

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7de8904
Optimize reverse neighbors for memory
mtdowling Oct 5, 2020
9f5ae00
Fix typo
mtdowling Oct 5, 2020
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27 changes: 20 additions & 7 deletions smithy-model/src/main/java/software/amazon/smithy/model/neighbor/NeighborProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,13 @@
package software.amazon.smithy.model.neighbor;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;
import software.amazon.smithy.model.Model;
import software.amazon.smithy.model.shapes.Shape;
import software.amazon.smithy.model.shapes.ShapeId;
Expand Down Expand Up @@ -122,13 +124,24 @@ static NeighborProvider reverse(Model model) {
* @return Returns the reverse neighbor provider.
*/
static NeighborProvider reverse(Model model, NeighborProvider forwardProvider) {
Map<ShapeId, List<Relationship>> targetedFrom = model.shapes()
.map(forwardProvider::getNeighbors)
.flatMap(List::stream)
.distinct()
.collect(Collectors.groupingBy(Relationship::getNeighborShapeId, ListUtils.toUnmodifiableList()));
// Note: this method previously needed lots of intermediate representations
// stored in memory to create a Map<ShapeId, List<RelationShip>> that contains
// only unique relationships. It was done using Stream, distinct, and groupingBy.
// However, when trying to load ridiculously large models, that approach consumes
// tons of heap. This approach allocates as little as possible (I think), but
// does require creating an ArrayList copy of a Set each time neighbors are returned.
Map<ShapeId, Set<Relationship>> targetedFrom = new HashMap<>();

return shape -> targetedFrom.getOrDefault(shape.getId(), ListUtils.of());
for (Shape shape : model.toSet()) {
for (Relationship rel : forwardProvider.getNeighbors(shape)) {
targetedFrom.computeIfAbsent(rel.getNeighborShapeId(), id -> new HashSet<>()).add(rel);
}
}

return shape -> {
Set<Relationship> shapes = targetedFrom.get(shape.getId());
return shapes == null ? Collections.emptyList() : ListUtils.copyOf(shapes);
};
}

/**
Expand Down