mayya-sharipova commented on a change in pull request #267:
URL: https://github.com/apache/lucene/pull/267#discussion_r700580884
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File path: lucene/core/src/java/org/apache/lucene/util/hnsw/HnswGraph.java
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@@ -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
Review comment:
Indeed, it is usually the case except these conditions:
1. When doing a hierarchical search. As we reach level 0, we use a single
`ep` found from the level 1 (`eps.length=1`), while topK is > 1.
2. When building a hierarchical graph. When adding a node, as we reach
`nodeLevel` - a starting level for this node, we use a single `ep` found
from the `level = nodeLevel + 1`, while using topk = efconstruction.
I am happy to discuss alternative API where we may not need topK even for
these cases, for exampling expanding `eps` array to have at least `topK`
elements.
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