gf2121 commented on code in PR #14935: URL: https://github.com/apache/lucene/pull/14935#discussion_r2201126320
########## lucene/benchmark-jmh/src/java/org/apache/lucene/benchmark/jmh/BitsetToArrayBenchmark.java: ########## @@ -0,0 +1,379 @@ +/* + * 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.benchmark.jmh; + +import java.util.SplittableRandom; +import java.util.concurrent.TimeUnit; +import java.util.stream.IntStream; +import org.openjdk.jmh.annotations.Benchmark; +import org.openjdk.jmh.annotations.BenchmarkMode; +import org.openjdk.jmh.annotations.Fork; +import org.openjdk.jmh.annotations.Level; +import org.openjdk.jmh.annotations.Measurement; +import org.openjdk.jmh.annotations.Mode; +import org.openjdk.jmh.annotations.OutputTimeUnit; +import org.openjdk.jmh.annotations.Param; +import org.openjdk.jmh.annotations.Scope; +import org.openjdk.jmh.annotations.Setup; +import org.openjdk.jmh.annotations.State; +import org.openjdk.jmh.annotations.Warmup; + +@BenchmarkMode(Mode.Throughput) +@OutputTimeUnit(TimeUnit.MICROSECONDS) +@State(Scope.Benchmark) +@Warmup(iterations = 3, time = 1) +@Measurement(iterations = 5, time = 1) +@Fork( + value = 1, + jvmArgsAppend = {"-Xmx1g", "-Xms1g", "-XX:+AlwaysPreTouch"}) +public class BitsetToArrayBenchmark { + + private final SplittableRandom R = new SplittableRandom(4314123142L); + + @Param({"5", "10", "20", "30", "40", "50", "60"}) + int bitCount; + + private final int[] scratch = new int[64]; + private long word; + private int[] resultArray; + private int base; + private int offset; + + @Setup(Level.Trial) + public void setup() { + base = R.nextInt(1000); + resultArray = new int[bitCount + Long.SIZE]; + } + + @Setup(Level.Invocation) + public void setupInvocation() { + word = 0L; + while (Long.bitCount(word) < bitCount) { + word |= 1L << R.nextInt(64); + } + offset = R.nextInt(64); + } + + @Benchmark + public int whileLoop() { + return _whileLoop(word, resultArray, offset, base); + } + + @Benchmark + public int forLoop() { + return _forLoop(word, resultArray, offset, base); + } + + @Benchmark + public int forLoopManualUnrolling() { + return _forLoopManualUnrolling(word, resultArray, offset, base); + } + + @Benchmark + public int dense() { + return _dense(word, resultArray, offset, base); + } + + @Benchmark + public int denseBranchLess() { + return _denseBranchLess(word, resultArray, offset, base); + } + + @Benchmark + public int denseBranchLessUnrolling() { + return _denseBranchLessUnrolling(word, resultArray, offset, base); + } + + @Benchmark + public int denseBranchLessVectorized() { + return _denseBranchLessVectorized(word, resultArray, offset, base, scratch); + } + + @Benchmark + public int denseInvert() { + return _denseInvert(word, resultArray, offset, base); + } + + @Benchmark + public int hybrid() { + return _hybrid(word, resultArray, offset, base, scratch); + } + + private static int _whileLoop(long word, int[] resultArray, int offset, int base) { + while (word != 0) { + int bit = Long.numberOfTrailingZeros(word); + resultArray[offset++] = base + bit; + word ^= 1L << bit; + } + return offset; + } + + private static int _forLoop(long word, int[] resultArray, int offset, int base) { + int to = offset + Long.bitCount(word); + for (int i = offset; i < to; i++) { + int bit = Long.numberOfTrailingZeros(word); + resultArray[i] = base + bit; + word ^= 1L << bit; + } + return to; + } + + private static int _forLoopManualUnrolling(long word, int[] resultArray, int offset, int base) { + int to = offset + Long.bitCount(word); + int i = offset; + + for (; i < to - 3; i += 4) { + int ntz = Long.numberOfTrailingZeros(word); + resultArray[i] = base + ntz; + word ^= 1L << ntz; + ntz = Long.numberOfTrailingZeros(word); + resultArray[i] = base + ntz; + word ^= 1L << ntz; + ntz = Long.numberOfTrailingZeros(word); + resultArray[i] = base + ntz; + word ^= 1L << ntz; + ntz = Long.numberOfTrailingZeros(word); + resultArray[i] = base + ntz; + word ^= 1L << ntz; + } + + for (; i < to; i++) { + int ntz = Long.numberOfTrailingZeros(word); + resultArray[i] = base + ntz; + word ^= 1L << ntz; + } + + return to; + } + + private static int _dense(long word, int[] resultArray, int offset, int base) { + for (int i = 0; i < Long.SIZE; i++) { + if ((word & (1L << i)) != 0) { + resultArray[offset++] = base + i; + } + } + return offset; + } + + private static int _denseBranchLess(long word, int[] resultArray, int offset, int base) { + int lWord = (int) word; + int hWord = (int) (word >>> 32); + for (int i = 0; i < Integer.SIZE; i++) { + resultArray[offset] = base + i; + offset += lWord & 1; + lWord >>>= 1; + } + for (int i = Integer.SIZE; i < Long.SIZE; i++) { + resultArray[offset] = base + i; + offset += hWord & 1; + hWord >>>= 1; + } + return offset; Review Comment: I find that it can be complied to `cmovne` when bitCount=20/30/40/50, but can not when bitCount=5/10/60. -- This is an automated message from the Apache Git Service. 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