kaivalnp commented on code in PR #14178: URL: https://github.com/apache/lucene/pull/14178#discussion_r1941904975
########## lucene/sandbox/src/java22/org/apache/lucene/sandbox/codecs/faiss/LibFaissC.java: ########## @@ -0,0 +1,268 @@ +/* + * 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.sandbox.codecs.faiss; + +import static java.lang.foreign.ValueLayout.ADDRESS; +import static java.lang.foreign.ValueLayout.JAVA_FLOAT; +import static java.lang.foreign.ValueLayout.JAVA_INT; +import static java.lang.foreign.ValueLayout.JAVA_LONG; + +import java.lang.foreign.Arena; +import java.lang.foreign.FunctionDescriptor; +import java.lang.foreign.Linker; +import java.lang.foreign.MemoryLayout; +import java.lang.foreign.MemorySegment; +import java.lang.foreign.SymbolLookup; +import java.lang.invoke.MethodHandle; +import java.nio.ByteOrder; +import java.nio.FloatBuffer; +import java.util.Locale; +import org.apache.lucene.index.FloatVectorValues; +import org.apache.lucene.index.KnnVectorValues; +import org.apache.lucene.index.VectorSimilarityFunction; +import org.apache.lucene.search.KnnCollector; +import org.apache.lucene.util.Bits; + +public final class LibFaissC { + public static final String LIBRARY_VERSION = "1.9.0"; + + static { + try { + System.loadLibrary("faiss_c"); + } catch (UnsatisfiedLinkError e) { + throw new RuntimeException( + "Shared library not found, build the Faiss C_API from https://github.com/facebookresearch/faiss/blob/main/c_api/INSTALL.md " + + "and link it (along with all dependencies) to the library path " + + "(-Djava.library.path JVM argument or $LD_LIBRARY_PATH environment variable)", + e); + } + checkLibraryVersion(); + } + + private LibFaissC() {} + + private static MethodHandle getMethodHandle( + String functionName, MemoryLayout resLayout, MemoryLayout... argLayouts) { + return Linker.nativeLinker() + .downcallHandle( + SymbolLookup.loaderLookup().find(functionName).orElseThrow(), + FunctionDescriptor.of(resLayout, argLayouts)); + } + + private static void checkLibraryVersion() { + MethodHandle getVersion = getMethodHandle("faiss_get_version", ADDRESS); + String actualVersion = callAndGetString(getVersion); + if (LIBRARY_VERSION.equals(actualVersion) == false) { + throw new UnsupportedOperationException( + String.format( + Locale.ROOT, + "Expected Faiss library version %s, found %s", + LIBRARY_VERSION, + actualVersion)); + } + } + + private static final MethodHandle FREE_INDEX = + getMethodHandle("faiss_Index_free", JAVA_INT, ADDRESS); + + public static void freeIndex(MemorySegment indexPointer) { + callAndHandleError(FREE_INDEX, indexPointer); + } + + private static final MethodHandle FREE_PARAMETER_SPACE = + getMethodHandle("faiss_ParameterSpace_free", JAVA_INT, ADDRESS); + + private static void freeParameterSpace(MemorySegment parameterSpacePointer) { + callAndHandleError(FREE_PARAMETER_SPACE, parameterSpacePointer); + } + + private static final MethodHandle INDEX_FACTORY = + getMethodHandle("faiss_index_factory", JAVA_INT, ADDRESS, JAVA_INT, ADDRESS, JAVA_INT); + + private static final MethodHandle PARAMETER_SPACE_NEW = + getMethodHandle("faiss_ParameterSpace_new", JAVA_INT, ADDRESS); + + private static final MethodHandle SET_INDEX_PARAMETERS = + getMethodHandle( + "faiss_ParameterSpace_set_index_parameters", JAVA_INT, ADDRESS, ADDRESS, ADDRESS); + + private static final MethodHandle INDEX_IS_TRAINED = + getMethodHandle("faiss_Index_is_trained", JAVA_INT, ADDRESS); + + private static final MethodHandle INDEX_TRAIN = + getMethodHandle("faiss_Index_train", JAVA_INT, ADDRESS, JAVA_LONG, ADDRESS); + + private static final MethodHandle INDEX_ADD = + getMethodHandle("faiss_Index_add", JAVA_INT, ADDRESS, JAVA_LONG, ADDRESS); + + public record Index(MemorySegment indexPointer, int[] ordToDoc) {} + + public static Index createIndex( + String description, + String indexParams, + VectorSimilarityFunction function, + FloatVectorValues floatVectorValues) { + + try (Arena temp = Arena.ofConfined()) { + int size = floatVectorValues.size(); + int dimension = floatVectorValues.dimension(); + + // Mapped from faiss/MetricType.h + int metric = + switch (function) { + case DOT_PRODUCT -> 0; + case EUCLIDEAN -> 1; + default -> throw new UnsupportedOperationException("metric type not supported"); + }; + + // Create an index + MemorySegment pointer = temp.allocate(ADDRESS); + callAndHandleError(INDEX_FACTORY, pointer, dimension, temp.allocateFrom(description), metric); + MemorySegment indexPointer = pointer.get(ADDRESS, 0); + + // Set index params + callAndHandleError(PARAMETER_SPACE_NEW, pointer); + MemorySegment parameterSpacePointer = + pointer.get(ADDRESS, 0).reinterpret(temp, LibFaissC::freeParameterSpace); + callAndHandleError( + SET_INDEX_PARAMETERS, + parameterSpacePointer, + indexPointer, + temp.allocateFrom(indexParams)); + + // Allocate docs in native memory + MemorySegment docs = temp.allocate(JAVA_FLOAT, (long) size * dimension); + FloatBuffer docsBuffer = docs.asByteBuffer().order(ByteOrder.nativeOrder()).asFloatBuffer(); + + int[] ordToDoc = new int[size]; + KnnVectorValues.DocIndexIterator iterator = floatVectorValues.iterator(); + for (int i = 0; i < size; i++) { + ordToDoc[i] = iterator.nextDoc(); + docsBuffer.put(floatVectorValues.vectorValue(iterator.index())); + } + + // Train index + if ((int) INDEX_IS_TRAINED.invokeExact(indexPointer) == 0) { + callAndHandleError(INDEX_TRAIN, indexPointer, size, docs); + } + + // Add docs to index + callAndHandleError(INDEX_ADD, indexPointer, size, docs); + + return new Index(indexPointer, ordToDoc); + } catch (Throwable t) { + throw new RuntimeException(t); + } + } + + private static final MethodHandle INDEX_WRITE = + getMethodHandle("faiss_write_index_fname", JAVA_INT, ADDRESS, ADDRESS); + + public static void indexWrite(MemorySegment indexPointer, String fileName) { + try (Arena temp = Arena.ofConfined()) { + callAndHandleError(INDEX_WRITE, indexPointer, temp.allocateFrom(fileName)); + } + } + + private static final MethodHandle INDEX_READ = + getMethodHandle("faiss_read_index_fname", JAVA_INT, ADDRESS, JAVA_INT, ADDRESS); + + public static MemorySegment indexRead(String fileName, int ioFlags) { + try (Arena temp = Arena.ofConfined()) { + MemorySegment pointer = temp.allocate(ADDRESS); + callAndHandleError(INDEX_READ, temp.allocateFrom(fileName), ioFlags, pointer); + return pointer.get(ADDRESS, 0); + } + } + + private static final MethodHandle INDEX_SEARCH = + getMethodHandle( + "faiss_Index_search", JAVA_INT, ADDRESS, JAVA_LONG, ADDRESS, JAVA_INT, ADDRESS, ADDRESS); + + public static void indexSearch( + MemorySegment indexPointer, + int[] ordToDoc, + float[] query, + KnnCollector knnCollector, + Bits acceptDocs) { + try (Arena temp = Arena.ofConfined()) { + // Allocate queries in native memory + MemorySegment queries = temp.allocate(JAVA_FLOAT, query.length); + queries.asByteBuffer().order(ByteOrder.nativeOrder()).asFloatBuffer().put(query); + + // Faiss knn search + int k = knnCollector.k(); + MemorySegment distancesPointer = temp.allocate(JAVA_FLOAT, k); + MemorySegment idsPointer = temp.allocate(JAVA_LONG, k); + + MemorySegment localIndex = indexPointer.reinterpret(temp, null); + callAndHandleError(INDEX_SEARCH, localIndex, 1, queries, k, distancesPointer, idsPointer); + + // Retrieve scores + float[] distances = new float[k]; + distancesPointer.asByteBuffer().order(ByteOrder.nativeOrder()).asFloatBuffer().get(distances); + + // Retrieve ids + long[] ids = new long[k]; + idsPointer.asByteBuffer().order(ByteOrder.nativeOrder()).asLongBuffer().get(ids); + + // Record hits + for (int i = 0; i < k; i++) { + int ord = (int) ids[i]; + if (ord < 0) { + break; + } + + // TODO: This is like a post-filter, include at runtime? + int doc = ordToDoc[ord]; + if (acceptDocs == null || acceptDocs.get(doc)) { + knnCollector.collect(doc, distances[i]); + } Review Comment: @benwtrent +1, filtering is super important.. I pulled the above PR + some more changes (explained in https://github.com/facebookresearch/faiss/pull/4167) locally, and got a filtered search working! Filtered searches in Lucene primarily use a [`FixedBits`](https://github.com/apache/lucene/blob/e4321619bba8669e93311ffb9456fa043d519b21/lucene/core/src/java/org/apache/lucene/util/FixedBits.java#L20) (in case of live docs) or [`FixedBitSet`](https://github.com/apache/lucene/blob/e4321619bba8669e93311ffb9456fa043d519b21/lucene/core/src/java/org/apache/lucene/util/FixedBitSet.java#L32) (in case of pre-filter). In both cases, these are backed by a `long[]` where each bit in a `long` represents whether a doc is filtered or not For i=0, we pick the least significant bit of the 1st `long` For i=1, we pick the second-least significant bit of the 1st `long` For i=64, we pick the least significant bit of the 2nd `long` .. and so on ([reference](https://github.com/apache/lucene/blob/e4321619bba8669e93311ffb9456fa043d519b21/lucene/core/src/java/org/apache/lucene/util/FixedBits.java#L31-L38)) Consequently in Faiss, we can use an [`IDSelectorBitmap`](https://github.com/facebookresearch/faiss/blob/6c046992a71e672df504a0101cddf6f2f2e90601/faiss/impl/IDSelector.h#L101) which takes `uint8_t*` (list of bytes) as input For i=0, we pick the least significant bit of the 1st `byte` For i=1, we pick the second-least significant bit of the 1st `byte` For i=8, we pick the least significant bit of the 2nd `byte` .. and so on ([reference](https://github.com/facebookresearch/faiss/blob/6c046992a71e672df504a0101cddf6f2f2e90601/faiss/impl/IDSelector.cpp#L117-L123)) i.e. we can bulk-copy the `long[]` from Java -> the native process in the [`LITTLE_ENDIAN`](https://en.wikipedia.org/wiki/Endianness) byte order and _directly use the resulting byte array as a filter!_ Lucene: ``` recall latency (ms) nDoc topK fanout maxConn beamWidth quantized index s index docs/s force merge s num segments index size (MB) selectivity filterType vec disk (MB) vec RAM (MB) 0.880 1.830 200000 100 50 32 200 no 143.77 1391.13 0.01 1 236.93 0.50 pre-filter 228.882 228.882 ``` Faiss: ``` recall latency (ms) nDoc topK fanout maxConn beamWidth quantized index s index docs/s force merge s num segments index size (MB) selectivity filterType vec disk (MB) vec RAM (MB) 0.792 1.000 200000 100 50 32 200 no 140.22 1426.38 0.00 1 511.97 0.50 pre-filter 228.882 228.882 ``` Added in the latest commit -- This is an automated message from the Apache Git Service. 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