mayya-sharipova commented on a change in pull request #267:
URL: https://github.com/apache/lucene/pull/267#discussion_r700574140
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File path: lucene/core/src/java/org/apache/lucene/util/hnsw/HnswGraph.java
##########
@@ -107,32 +113,82 @@ public static NeighborQueue search(
Random random)
throws IOException {
int size = graphValues.size();
+ int boundedNumSeed = Math.min(numSeed, 2 * size);
+ NeighborQueue results;
+
+ if (graphValues.maxLevel() == 0) {
+ // search in SNW; generate a number of entry points randomly
+ final int[] eps = new int[boundedNumSeed];
+ for (int i = 0; i < boundedNumSeed; i++) {
+ eps[i] = random.nextInt(size);
+ }
+ return searchLevel(query, topK, 0, eps, vectors, similarityFunction,
graphValues, acceptOrds);
+ } else {
+ // search in hierarchical SNW
+ int[] eps = new int[] {graphValues.entryNode()};
+ for (int level = graphValues.maxLevel(); level >= 1; level--) {
+ results =
+ HnswGraph.searchLevel(
+ query, 1, level, eps, vectors, similarityFunction,
graphValues, acceptOrds);
+ eps = new int[] {results.pop()};
+ }
+ results =
+ HnswGraph.searchLevel(
+ query, boundedNumSeed, 0, eps, vectors, similarityFunction,
graphValues, acceptOrds);
+ while (results.size() > topK) {
+ results.pop();
+ }
+ return results;
+ }
+ }
+ /**
+ * Searches for the nearest neighbors of a query vector in a given level
+ *
+ * @param query search query vector
+ * @param topK the number of nearest to query results to return
+ * @param level level to search
+ * @param eps the entry points for search at this level
+ * @param vectors vector values
+ * @param similarityFunction similarity function
+ * @param graphValues the graph values
+ * @param acceptOrds {@link Bits} that represents the allowed document
ordinals to match, or
+ * {@code null} if they are all allowed to match.
+ * @return a priority queue holding the closest neighbors found
+ */
+ static NeighborQueue searchLevel(
+ float[] query,
+ int topK,
+ int level,
+ final int[] eps,
+ RandomAccessVectorValues vectors,
+ VectorSimilarityFunction similarityFunction,
+ KnnGraphValues graphValues,
+ Bits acceptOrds)
+ throws IOException {
+
+ int size = graphValues.size();
+ int queueSize = Math.max(eps.length, topK);
// MIN heap, holding the top results
- NeighborQueue results = new NeighborQueue(numSeed,
similarityFunction.reversed);
+ NeighborQueue results = new NeighborQueue(queueSize,
similarityFunction.reversed);
// MAX heap, from which to pull the candidate nodes
- NeighborQueue candidates = new NeighborQueue(numSeed,
!similarityFunction.reversed);
-
+ NeighborQueue candidates = new NeighborQueue(queueSize,
!similarityFunction.reversed);
// set of ordinals that have been visited by search on this layer, used to
avoid backtracking
SparseFixedBitSet visited = new SparseFixedBitSet(size);
- // get initial candidates at random
- int boundedNumSeed = Math.min(numSeed, 2 * size);
- for (int i = 0; i < boundedNumSeed; i++) {
- int entryPoint = random.nextInt(size);
- if (visited.get(entryPoint) == false) {
- visited.set(entryPoint);
- // explore the topK starting points of some random numSeed probes
- float score = similarityFunction.compare(query,
vectors.vectorValue(entryPoint));
- candidates.add(entryPoint, score);
- if (acceptOrds == null || acceptOrds.get(entryPoint)) {
- results.add(entryPoint, score);
+
+ for (int i = 0; i < eps.length; i++) {
Review comment:
Good comment, addressed in 6a05951772cc72a1530f3fd863d906dc0e3bef88
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