> Original mail: > https://mail.openjdk.java.net/pipermail/core-libs-dev/2020-September/069197.html > > Hello, > > while working with `StringBuilder.insert()` I've spotted that its delegate > `AbstractStringBuilder.insert()` is missing > a fast-path for the most frequent case when its argument is `String`. > > Previously they did similart optimization for > `StirngBuilder.append(CharSequence, int, int)`, > see https://bugs.openjdk.java.net/browse/JDK-8224986 > > I'd like to contribute a trivial patch that brings improvement for the case > when SB's content is Latin1 > and inserted String is Latin1 as well. > > To measure improvement I've used simple benchmark: > @BenchmarkMode(Mode.AverageTime) > @OutputTimeUnit(TimeUnit.NANOSECONDS) > @Fork(jvmArgsAppend = {"-Xms2g", "-Xmx2g"}) > public class StringBuilderInsertBenchmark { > > @Benchmark > public StringBuilder insert(Data data) { > String string = data.string; > return new StringBuilder().append("ABC").insert(1, string, 1, data.length > + 1); > } > > @State(Scope.Thread) > public static class Data { > String string; > > @Param({"true", "false"}) > private boolean latin; > > @Param({"8", "64", "128", "1024"}) > private int length; > > @Setup > public void setup() { > String alphabet = latin > ? "abcdefghijklmnopqrstuvwxyz" // English > : "абвгдеёжзиклмнопрстуфхцчшщьыъэюя"; // Russian > > string = new RandomStringGenerator().randomString(alphabet, length + 2); > } > } > } > > public final class RandomStringGenerator { > > public String randomString(String alphabet, int length) { > char[] chars = alphabet.toCharArray(); > > ThreadLocalRandom random = ThreadLocalRandom.current(); > > char[] array = new char[length]; > for (int i = 0; i < length; i++) { > array[i] = chars[random.nextInt(chars.length)]; > } > > return new String(array); > } > } > Which gives > > (latin) (length) original patched Units > insert true 8 24.2 ± 0.1 22.2 ± 0.0 ns/op > insert true 64 53.8 ± 0.2 36.1 ± 0.1 ns/op > insert true 128 80.9 ± 0.2 44.6 ± 0.0 ns/op > insert true 1024 365.4 ± 0.5 109.8 ± 3.9 ns/op > > insert false 8 33.5 ± 0.5 32.3 ± 0.2 ns/op > insert false 64 73.2 ± 0.3 73.2 ± 0.2 ns/op > insert false 128 103.9 ± 0.6 103.3 ± 0.1 ns/op > insert false 1024 576.5 ± 4.8 569.5 ± 2.0 ns/op > Patch is attached. As of tests tier1 and tier2 are ok. > > With best regards, > Sergey Tsypanov
Сергей Цыпанов has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision: - Merge branch 'master' into asb - 8254082: Add fast-path for String into AbstractStringBuilder.insert(int, CharSequence, int, int) ------------- Changes: - all: https://git.openjdk.java.net/jdk/pull/402/files - new: https://git.openjdk.java.net/jdk/pull/402/files/128cce75..f7e7b4fe Webrevs: - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=402&range=01 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=402&range=00-01 Stats: 556828 lines in 5364 files changed: 448654 ins; 76031 del; 32143 mod Patch: https://git.openjdk.java.net/jdk/pull/402.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/402/head:pull/402 PR: https://git.openjdk.java.net/jdk/pull/402
