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Speed up advancing within a block, take 2. (#13958)
PR #13692 tried to speed up advancing by using branchless binary search, but while this yielded a speedup on my machine, this yielded a slowdown on nightly benchmarks. This PR tries a different approach using vectorization. Experimentation suggests that it speeds up queries that advance to the next few doc IDs, such as `AndHighHigh`.
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lucene/benchmark-jmh/src/java/org/apache/lucene/benchmark/jmh/AdvanceBenchmark.java
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/* | ||
* 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; | ||
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import java.util.Arrays; | ||
import java.util.Random; | ||
import java.util.concurrent.TimeUnit; | ||
import org.apache.lucene.search.DocIdSetIterator; | ||
import org.apache.lucene.util.VectorUtil; | ||
import org.openjdk.jmh.annotations.Benchmark; | ||
import org.openjdk.jmh.annotations.BenchmarkMode; | ||
import org.openjdk.jmh.annotations.CompilerControl; | ||
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.Scope; | ||
import org.openjdk.jmh.annotations.Setup; | ||
import org.openjdk.jmh.annotations.State; | ||
import org.openjdk.jmh.annotations.Warmup; | ||
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@BenchmarkMode(Mode.Throughput) | ||
@OutputTimeUnit(TimeUnit.MILLISECONDS) | ||
@State(Scope.Benchmark) | ||
@Warmup(iterations = 5, time = 1) | ||
@Measurement(iterations = 5, time = 1) | ||
@Fork( | ||
value = 3, | ||
jvmArgsAppend = { | ||
"-Xmx1g", | ||
"-Xms1g", | ||
"-XX:+AlwaysPreTouch", | ||
"--add-modules", | ||
"jdk.incubator.vector" | ||
}) | ||
public class AdvanceBenchmark { | ||
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private final long[] values = new long[129]; | ||
private final int[] startIndexes = new int[1_000]; | ||
private final long[] targets = new long[startIndexes.length]; | ||
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@Setup(Level.Trial) | ||
public void setup() throws Exception { | ||
for (int i = 0; i < 128; ++i) { | ||
values[i] = i; | ||
} | ||
values[128] = DocIdSetIterator.NO_MORE_DOCS; | ||
Random r = new Random(0); | ||
for (int i = 0; i < startIndexes.length; ++i) { | ||
startIndexes[i] = r.nextInt(64); | ||
targets[i] = startIndexes[i] + 1 + r.nextInt(1 << r.nextInt(7)); | ||
} | ||
} | ||
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@Benchmark | ||
public void binarySearch() { | ||
for (int i = 0; i < startIndexes.length; ++i) { | ||
binarySearch(values, targets[i], startIndexes[i]); | ||
} | ||
} | ||
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@CompilerControl(CompilerControl.Mode.DONT_INLINE) | ||
private static int binarySearch(long[] values, long target, int startIndex) { | ||
// Standard binary search | ||
int i = Arrays.binarySearch(values, startIndex, values.length, target); | ||
if (i < 0) { | ||
i = -1 - i; | ||
} | ||
return i; | ||
} | ||
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@Benchmark | ||
public void inlinedBranchlessBinarySearch() { | ||
for (int i = 0; i < targets.length; ++i) { | ||
inlinedBranchlessBinarySearch(values, targets[i]); | ||
} | ||
} | ||
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@CompilerControl(CompilerControl.Mode.DONT_INLINE) | ||
private static int inlinedBranchlessBinarySearch(long[] values, long target) { | ||
// This compiles to cmov instructions. | ||
int start = 0; | ||
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if (values[63] < target) { | ||
start += 64; | ||
} | ||
if (values[start + 31] < target) { | ||
start += 32; | ||
} | ||
if (values[start + 15] < target) { | ||
start += 16; | ||
} | ||
if (values[start + 7] < target) { | ||
start += 8; | ||
} | ||
if (values[start + 3] < target) { | ||
start += 4; | ||
} | ||
if (values[start + 1] < target) { | ||
start += 2; | ||
} | ||
if (values[start] < target) { | ||
start += 1; | ||
} | ||
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return start; | ||
} | ||
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@Benchmark | ||
public void linearSearch() { | ||
for (int i = 0; i < startIndexes.length; ++i) { | ||
linearSearch(values, targets[i], startIndexes[i]); | ||
} | ||
} | ||
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@CompilerControl(CompilerControl.Mode.DONT_INLINE) | ||
private static int linearSearch(long[] values, long target, int startIndex) { | ||
// Naive linear search. | ||
for (int i = startIndex; i < values.length; ++i) { | ||
if (values[i] >= target) { | ||
return i; | ||
} | ||
} | ||
return values.length; | ||
} | ||
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@Benchmark | ||
public void vectorUtilSearch() { | ||
for (int i = 0; i < startIndexes.length; ++i) { | ||
VectorUtil.findNextGEQ(values, 128, targets[i], startIndexes[i]); | ||
} | ||
} | ||
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@CompilerControl(CompilerControl.Mode.DONT_INLINE) | ||
private static int vectorUtilSearch(long[] values, long target, int startIndex) { | ||
return VectorUtil.findNextGEQ(values, 128, target, startIndex); | ||
} | ||
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private static void assertEquals(int expected, int actual) { | ||
if (expected != actual) { | ||
throw new AssertionError("Expected: " + expected + ", got " + actual); | ||
} | ||
} | ||
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public static void main(String[] args) { | ||
// For testing purposes | ||
long[] values = new long[129]; | ||
for (int i = 0; i < 128; ++i) { | ||
values[i] = i; | ||
} | ||
values[128] = DocIdSetIterator.NO_MORE_DOCS; | ||
for (int start = 0; start < 128; ++start) { | ||
for (int targetIndex = start; targetIndex < 128; ++targetIndex) { | ||
int actualIndex = binarySearch(values, values[targetIndex], start); | ||
assertEquals(targetIndex, actualIndex); | ||
actualIndex = inlinedBranchlessBinarySearch(values, values[targetIndex]); | ||
assertEquals(targetIndex, actualIndex); | ||
actualIndex = linearSearch(values, values[targetIndex], start); | ||
assertEquals(targetIndex, actualIndex); | ||
actualIndex = vectorUtilSearch(values, values[targetIndex], start); | ||
assertEquals(targetIndex, actualIndex); | ||
} | ||
} | ||
} | ||
} |
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