rmuir commented on code in PR #13636: URL: https://github.com/apache/lucene/pull/13636#discussion_r1710505009
########## lucene/core/src/java21/org/apache/lucene/internal/vectorization/MemorySegmentPostingDecodingUtil.java: ########## @@ -0,0 +1,109 @@ +/* + * 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.internal.vectorization; + +import java.io.IOException; +import java.lang.foreign.MemorySegment; +import java.nio.ByteOrder; +import jdk.incubator.vector.LongVector; +import jdk.incubator.vector.VectorOperators; +import jdk.incubator.vector.VectorSpecies; +import org.apache.lucene.store.IndexInput; + +final class MemorySegmentPostingDecodingUtil extends PostingDecodingUtil { + + private static final VectorSpecies<Long> LONG_SPECIES = + PanamaVectorConstants.PRERERRED_LONG_SPECIES; + + private final IndexInput in; + private final MemorySegment memorySegment; + + MemorySegmentPostingDecodingUtil(IndexInput in, MemorySegment memorySegment) { + this.in = in; + this.memorySegment = memorySegment; + } + + @Override + public void readLongs(int count, long[] b) throws IOException { + if (count < LONG_SPECIES.length()) { + in.readLongs(b, 0, count); + } else { + long offset = in.getFilePointer(); + long endOffset = offset + count * Long.BYTES; + int loopBound = LONG_SPECIES.loopBound(count - 1); + for (int i = 0; + i < loopBound; + i += LONG_SPECIES.length(), offset += LONG_SPECIES.length() * Long.BYTES) { + LongVector.fromMemorySegment(LONG_SPECIES, memorySegment, offset, ByteOrder.LITTLE_ENDIAN) + .intoArray(b, i); + } + + // Handle the tail by reading a vector that is aligned with with `count` on the right side. + int i = count - LONG_SPECIES.length(); + offset = endOffset - LONG_SPECIES.length() * Long.BYTES; + LongVector.fromMemorySegment(LONG_SPECIES, memorySegment, offset, ByteOrder.LITTLE_ENDIAN) + .intoArray(b, i); + + in.seek(endOffset); + } + } + + @Override + public void splitLongs(int count, long[] b, int bShift, long bMask, long[] c, long cMask) + throws IOException { + if (count < LONG_SPECIES.length()) { + // Not enough data to vectorize without going out-of-bounds. In practice, this branch is never + // used if the bit width is 256, and is used for 2 and 3 bits per value if the bit width is + // 512. + in.readLongs(c, 0, count); + for (int i = 0; i < count; ++i) { + b[i] = (c[i] >>> bShift) & bMask; + c[i] &= cMask; + } + } else { + long offset = in.getFilePointer(); + long endOffset = offset + count * Long.BYTES; + int loopBound = LONG_SPECIES.loopBound(count - 1); Review Comment: why the `loopBound(N - 1)` ? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
