List allocation benchmark

main.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/widgets.dart';

List<int> generateWithElement() {
  return <int>[
    for (int i = 0; i < 1000; i++)
      i
  ];
}

List<int> generateWithFilled() {
  return List<int>.generate(1000, fill);
}


List<int> preallocate() {
  var result = List<int>(1000);
  for (int i = 0; i < 1000; i++)
    result[i] = i;
  return result;
}

List<int> listAdd() {
  var result = <int>[];
  for (int i = 0; i < 1000; i++)
    result.add(i);
  return result;
}

int fill(int value) {
  return value;
}

void main() {
  var sw = Stopwatch();
  sw.start();
  List<int> result;
  for (var i = 0; i < 100; i++) {
    result = generateWithElement();
  }
  sw.stop();
  print(result.last);
  print('for element took ${sw.elapsedMicroseconds}');

  sw.reset();
  sw.start();
  for (var i = 0; i < 100; i++) {
    result = generateWithFilled();
  }
  sw.stop();
  print(result.last);
  print('List.generate took ${sw.elapsedMicroseconds}');

  sw.reset();
  sw.start();
  for (var i = 0; i < 100; i++) {
    result = preallocate();
  }
  sw.stop();
  print(result.last);
  print('preallocate took ${sw.elapsedMicroseconds}');

  sw.reset();
  sw.start();
  for (var i = 0; i < 100; i++) {
    result = listAdd();
  }
  sw.stop();
  print(result.last);
  print('List.add took ${sw.elapsedMicroseconds}');
}

The best way to run this is to comment out all but 1.