jbellis commented on code in PR #12254: URL: https://github.com/apache/lucene/pull/12254#discussion_r1187897579
########## lucene/core/src/java/org/apache/lucene/util/hnsw/ConcurrentHnswGraphBuilder.java: ########## @@ -0,0 +1,329 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.lucene.util.hnsw; + +import static java.lang.Math.log; + +import java.io.IOException; +import java.util.Objects; +import java.util.concurrent.ConcurrentSkipListSet; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.Semaphore; +import java.util.concurrent.ThreadLocalRandom; +import java.util.concurrent.ThreadPoolExecutor; +import java.util.concurrent.TimeUnit; +import org.apache.lucene.index.VectorEncoding; +import org.apache.lucene.index.VectorSimilarityFunction; +import org.apache.lucene.util.AtomicBitSet; +import org.apache.lucene.util.FixedBitSet; +import org.apache.lucene.util.InfoStream; +import org.apache.lucene.util.NamedThreadFactory; +import org.apache.lucene.util.hnsw.ConcurrentOnHeapHnswGraph.NodeAtLevel; + +/** + * Builder for Concurrent HNSW graph. See {@link HnswGraph} for a high level overview, and the + * comments to `addGraphNode` for details on the concurrent building approach. + * + * @param <T> the type of vector + */ +public final class ConcurrentHnswGraphBuilder<T> implements IHnswGraphBuilder<T> { + + /** Default number of maximum connections per node */ + public static final int DEFAULT_MAX_CONN = 16; + + /** + * Default number of the size of the queue maintained while searching during a graph construction. + */ + public static final int DEFAULT_BEAM_WIDTH = 100; + + /** A name for the HNSW component for the info-stream * */ + public static final String HNSW_COMPONENT = "HNSW"; + + private final int beamWidth; + private final double ml; + private final ThreadLocal<NeighborArray> scratchNeighbors; + + private final VectorSimilarityFunction similarityFunction; + private final VectorEncoding vectorEncoding; + private final RandomAccessVectorValues<T> vectors; + private final ThreadLocal<HnswGraphSearcher<T>> graphSearcher; + + final ConcurrentOnHeapHnswGraph hnsw; + private final ConcurrentSkipListSet<NodeAtLevel> insertionsInProgress = + new ConcurrentSkipListSet<>(); + + private InfoStream infoStream = InfoStream.getDefault(); + + // we need two sources of vectors in order to perform diversity check comparisons without + // colliding + private final RandomAccessVectorValues<T> vectorsCopy; + private final AtomicBitSet initializedNodes; + + /** + * Reads all the vectors from vector values, builds a graph connecting them by their dense + * ordinals, using the given hyperparameter settings, and returns the resulting graph. + * + * @param vectors the vectors whose relations are represented by the graph - must provide a + * different view over those vectors than the one used to add via addGraphNode. + * @param M – graph fanout parameter used to calculate the maximum number of connections a node + * can have – M on upper layers, and M * 2 on the lowest level. + * @param beamWidth the size of the beam search to use when finding nearest neighbors. + */ + public ConcurrentHnswGraphBuilder( + RandomAccessVectorValues<T> vectors, + VectorEncoding vectorEncoding, + VectorSimilarityFunction similarityFunction, + int M, + int beamWidth) + throws IOException { + this.vectors = vectors; + this.vectorsCopy = vectors.copy(); + this.vectorEncoding = Objects.requireNonNull(vectorEncoding); + this.similarityFunction = Objects.requireNonNull(similarityFunction); + if (M <= 0) { + throw new IllegalArgumentException("maxConn must be positive"); + } + if (beamWidth <= 0) { + throw new IllegalArgumentException("beamWidth must be positive"); + } + this.beamWidth = beamWidth; + // normalization factor for level generation; currently not configurable + this.ml = M == 1 ? 1 : 1 / Math.log(1.0 * M); + this.hnsw = new ConcurrentOnHeapHnswGraph(M); + this.graphSearcher = Review Comment: Can do. -- This is an automated message from the Apache Git Service. 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