blob: aec9789839a1a72a4d3e1fcc7c49781ebf25dfe0 [file] [log] [blame]
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
// Test that the default PRNG does converge towards Pi when doing a Monte Carlo
// simulation.
// Library tag to allow Dartium to run the test.
library pi_test;
import "package:expect/expect.dart";
import 'dart:math';
var known_bad_seeds = const [50051, 55597, 59208];
void main([args]) {
// Select a seed either from the argument passed in or
// otherwise a random seed.
var seed = -1;
if ((args != null) && (args.length > 0)) {
seed = int.parse(args[0]);
} else {
var seed_prng = new Random();
while (seed == -1) {
seed = seed_prng.nextInt(1 << 16);
if (known_bad_seeds.contains(seed)) {
// Reset seed and try again.
seed = -1;
}
}
}
// Setup the PRNG for the Monte Carlo simulation.
print("pi_test seed: $seed");
var prng = new Random(seed);
var outside = 0;
var inside = 0;
for (var i = 0; i < 600000; i++) {
var x = prng.nextDouble();
var y = prng.nextDouble();
if ((x * x) + (y * y) < 1.0) {
inside++;
} else {
outside++;
}
}
// Mmmmh, Pie!
var pie = 4.0 * (inside / (inside + outside));
print("$pie");
Expect.isTrue(((PI - 0.009) < pie) && (pie < (PI + 0.009)));
}