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DmitryNekrasovDmitryNekrasov
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The performance of creating new datetime formats can be improved (#585)
- Refactor `ParserStructure.concat` to streamline operation merging logic - Add `unconditionalModifications` promotion optimization - Add JMH benchmarks for common datetime formats (ISO, RFC 1123, UTC offset) - Add `ParserStructureConcatenationTest` for concat behavior verification Fixes #571
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‎benchmarks/src/jmh/kotlin/CommonFormats.kt‎

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/*
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* Copyright 2019-2025 JetBrains s.r.o. and contributors.
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* Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
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*/
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@file:Suppress("unused")
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package kotlinx.datetime
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import kotlinx.datetime.format.*
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import org.openjdk.jmh.annotations.*
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import org.openjdk.jmh.infra.Blackhole
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import java.util.concurrent.*
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@Warmup(iterations = 20, time = 2)
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@Measurement(iterations = 30, time = 2)
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@BenchmarkMode(Mode.AverageTime)
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@OutputTimeUnit(TimeUnit.NANOSECONDS)
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@State(Scope.Benchmark)
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@Fork(2)
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open class CommonFormats {
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@Benchmark
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fun buildPythonDateTimeFormat(blackhole: Blackhole) {
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val v = LocalDateTime.Format {
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year()
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char('-')
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monthNumber()
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char('-')
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day()
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char(' ')
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hour()
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char(':')
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minute()
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optional {
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char(':')
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second()
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optional {
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char('.')
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secondFraction()
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}
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}
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}
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blackhole.consume(v)
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}
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@Benchmark
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fun buildIsoDateTimeFormat(blackhole: Blackhole) {
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val format = LocalDateTime.Format {
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date(LocalDate.Format {
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year()
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char('-')
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monthNumber()
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char('-')
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day()
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})
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alternativeParsing({ char('t') }) { char('T') }
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time(LocalTime.Format {
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hour()
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char(':')
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minute()
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alternativeParsing({}) {
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char(':')
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second()
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optional {
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char('.')
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secondFraction(1, 9)
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}
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}
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})
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}
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blackhole.consume(format)
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}
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@Benchmark
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fun buildFourDigitsUtcOffsetFormat(blackhole: Blackhole) {
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val format = UtcOffset.Format {
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offsetHours()
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offsetMinutesOfHour()
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}
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blackhole.consume(format)
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}
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@Benchmark
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fun buildRfc1123DateTimeFormat(blackhole: Blackhole) {
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val format = DateTimeComponents.Format {
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alternativeParsing({
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// the day of week may be missing
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}) {
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dayOfWeek(DayOfWeekNames.ENGLISH_ABBREVIATED)
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chars(", ")
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}
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day(Padding.NONE)
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char(' ')
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monthName(MonthNames.ENGLISH_ABBREVIATED)
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char(' ')
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year()
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char(' ')
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hour()
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char(':')
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minute()
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optional {
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char(':')
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second()
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}
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chars(" ")
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alternativeParsing({
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chars("UT")
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}, {
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chars("Z")
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}) {
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optional("GMT") {
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offset(UtcOffset.Format {
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offsetHours()
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offsetMinutesOfHour()
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})
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}
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}
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}
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blackhole.consume(format)
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}
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@Benchmark
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fun buildIsoDateTimeOffsetFormat(blackhole: Blackhole) {
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val format = DateTimeComponents.Format {
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date(LocalDate.Format {
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year()
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char('-')
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monthNumber()
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char('-')
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day()
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})
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alternativeParsing({
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char('t')
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}) {
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char('T')
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}
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hour()
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char(':')
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minute()
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char(':')
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second()
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optional {
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char('.')
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secondFraction(1, 9)
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}
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alternativeParsing({
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offsetHours()
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}) {
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offset(UtcOffset.Format {
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alternativeParsing({ chars("z") }) {
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optional("Z") {
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offsetHours()
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char(':')
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offsetMinutesOfHour()
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optional {
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char(':')
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offsetSecondsOfMinute()
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}
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}
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}
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})
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}
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}
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blackhole.consume(format)
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}
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}

‎benchmarks/src/jmh/kotlin/ParallelFormatBenchmark.kt‎

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/*
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* Copyright 2019-2025 JetBrains s.r.o. and contributors.
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* Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
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*/
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@file:Suppress("unused")
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package kotlinx.datetime
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import kotlinx.datetime.format.alternativeParsing
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import kotlinx.datetime.format.char
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import org.openjdk.jmh.annotations.*
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import org.openjdk.jmh.infra.Blackhole
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import java.util.concurrent.TimeUnit
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@Warmup(iterations = 10, time = 2)
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@Measurement(iterations = 20, time = 2)
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@BenchmarkMode(Mode.AverageTime)
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@OutputTimeUnit(TimeUnit.NANOSECONDS)
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@State(Scope.Benchmark)
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@Fork(1)
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open class ParallelFormatBenchmark {
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@Param("2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12")
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var n = 0
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@Benchmark
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fun formatCreationWithAlternativeParsing(blackhole: Blackhole) {
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val format = LocalDateTime.Format {
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repeat(n) {
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alternativeParsing(
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{ monthNumber() },
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{ day() },
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primaryFormat = { hour() }
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)
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char('@')
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minute()
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char('#')
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second()
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}
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}
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blackhole.consume(format)
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}
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@Benchmark
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fun formatCreationWithNestedAlternativeParsing(blackhole: Blackhole) {
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val format = LocalDateTime.Format {
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repeat(n) { index ->
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alternativeParsing(
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{ monthNumber(); char('-'); day() },
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{ day(); char('/'); monthNumber() },
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primaryFormat = { year(); char('-'); monthNumber(); char('-'); day() }
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)
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if (index and 1 == 0) {
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alternativeParsing(
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{
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alternativeParsing(
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{ hour(); char(':'); minute() },
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{ minute(); char(':'); second() },
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primaryFormat = { hour(); char(':'); minute(); char(':'); second() }
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)
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},
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primaryFormat = {
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year(); char('-'); monthNumber(); char('-'); day()
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char('T')
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hour(); char(':'); minute(); char(':'); second()
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}
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)
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}
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char('|')
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if (index % 3 == 0) {
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char('|')
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}
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if (index and 2 == 0) {
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alternativeParsing(
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{ char('Z') },
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{ char('+'); hour(); char(':'); minute() },
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primaryFormat = { char('-'); hour(); char(':'); minute() }
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)
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}
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}
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}
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blackhole.consume(format)
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}
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}

‎benchmarks/src/jmh/kotlin/SerialFormatBenchmark.kt‎

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/*
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* Copyright 2019-2025 JetBrains s.r.o. and contributors.
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* Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
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*/
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@file:Suppress("unused")
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package kotlinx.datetime
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import kotlinx.datetime.format.char
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import org.openjdk.jmh.annotations.*
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import org.openjdk.jmh.infra.Blackhole
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import java.util.concurrent.TimeUnit
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@Warmup(iterations = 10, time = 2)
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@Measurement(iterations = 20, time = 2)
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@BenchmarkMode(Mode.AverageTime)
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@OutputTimeUnit(TimeUnit.NANOSECONDS)
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@State(Scope.Benchmark)
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@Fork(1)
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open class SerialFormatBenchmark {
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@Param("1", "2", "4", "8", "16", "32", "64", "128", "256", "512", "1024")
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var n = 0
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@Benchmark
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fun largeSerialFormat(blackhole: Blackhole) {
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val format = LocalDateTime.Format {
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repeat(n) {
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char('^')
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monthNumber()
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char('&')
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day()
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char('!')
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hour()
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char('$')
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minute()
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char('#')
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second()
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char('@')
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}
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}
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blackhole.consume(format)
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}
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}

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