Dart Loop Benchmarking

main.dart

// Adding this line so we can perform the variable assignment: num eachElement = 0;
// ignore_for_file: unused_local_variable

import 'dart:collection';
import 'dart:math';

void main(List<String> args) {
  final list = UnmodifiableListView(
    List<int>.generate(200000000, (index) => index),
  );

  final results = {
    'While-Loop Uncached Length':
        benchmarck(() => whileLoopUncachedLength(list)),
    'While-Loop Cached Length': benchmarck(() => whileLoopCachedLength(list)),
    'While-Loop Reversed': benchmarck(() => whileLoopReversed(list)),
    'For-Loop Uncached Length': benchmarck(() => forLoopUncachedLength(list)),
    'For-Loop Cached Length': benchmarck(() => forLoopCachedLength(list)),
    'For Loop Reversed': benchmarck(() => forLoopReversed(list)),
    'For-In Loop': benchmarck(() => forInLoop(list)),
    'For-Each Loop': benchmarck(() => forEachLoop(list)),
  };

  final elements = results.entries.toList()
    ..sort((a, b) => a.value > b.value ? -1 : 1);
  print('ms\tLoop');
  for (var entry in elements) {
    print('${entry.value}\t${entry.key}');
  }
}

int benchmarck(void Function() function) {
  final stopwatch = Stopwatch()..start();
  function();
  stopwatch.stop();
  return stopwatch.elapsedMilliseconds;
}

void whileLoopUncachedLength(List<int> list) {
  var count = 0;
  num eachElement = 0;
  while (count < list.length) {
    eachElement = pow(list[count], 3);
    count++;
  }
}

void whileLoopCachedLength(List<int> list) {
  var count = 0;
  num eachElement = 0;
  final length = list.length;
  while (count < length) {
    eachElement = pow(list[count], 3);
    count++;
  }
}

void whileLoopReversed(List<int> list) {
  var count = list.length - 1;
  num eachElement = 0;
  while (count >= 0) {
    eachElement = pow(list[count], 3);
    count--;
  }
}

void forLoopUncachedLength(List<int> list) {
  num eachElement = 0;
  for (var i = 0; i < list.length; i++) {
    eachElement = pow(list[i], 3);
  }
}

void forLoopCachedLength(List<int> list) {
  num eachElement = 0;
  var length = list.length;
  for (var i = 0; i < length; i++) {
    eachElement = pow(list[i], 3);
  }
}

void forLoopReversed(List<int> list) {
  num eachElement = 0;
  for (var i = list.length - 1; i >= 0; i--) {
    eachElement = pow(list[i], 3);
  }
}

void forInLoop(List<int> list) {
  num eachElement = 0;

  for (var element in list) {
    eachElement = pow(element, 3);
  }
}

void forEachLoop(List<int> list) {
  num eachElement = 0;
  void fn(int element) => eachElement = pow(element, 3);
  list.forEach(fn);
}

results.md

Loop Benchmarks

The loops that are tested itereate over a list with 200,000,000 elements. The value at each index is the index itself.

dart --version
Dart SDK version: 2.18.6 (stable) (Tue Dec 13 21:15:14 2022 +0000) on "macos_x64"

dart run main.dart

ms	Loop
1013	For-Each Loop
543	For-In Loop
256	For Loop Reversed
254	For-Loop Cached Length
254	While-Loop Reversed
254	While-Loop Cached Length
202	For-Loop Uncached Length
198	While-Loop Uncached Length

dart compile aot-snapshot main.dart && dartaotruntime main.aot

ms	Loop
1199	For-In Loop
981	For-Each Loop
148	For Loop Reversed
148	While-Loop Uncached Length
147	While-Loop Cached Length
146	While-Loop Reversed
145	For-Loop Cached Length
144	For-Loop Uncached Length

dart compile exe main.dart && ./main.exe

ms	Loop
1234	For-In Loop
966	For-Each Loop
161	For Loop Reversed
161	While-Loop Reversed
158	For-Loop Uncached Length
157	While-Loop Cached Length
156	For-Loop Cached Length
152	While-Loop Uncached Length

dart compile jit-snapshot main.dart

ms	Loop
1136	For-Each Loop
599	For-In Loop
264	For Loop Reversed
257	While-Loop Reversed
254	For-Loop Cached Length
253	While-Loop Cached Length
206	While-Loop Uncached Length
203	For-Loop Uncached Length

dart compile kernel main.dart && dart run ./main.dill

ms	Loop
989	For-Each Loop
589	For-In Loop
254	For Loop Reversed
254	While-Loop Reversed
253	For-Loop Cached Length
251	While-Loop Cached Length
203	While-Loop Uncached Length
202	For-Loop Uncached Length