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| 1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file | 1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a | 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. | 3 // BSD-style license that can be found in the LICENSE file. |
| 4 | 4 |
| 5 // Test that the default PRNG does converge towards Pi when doing a Monte Carlo | 5 // Test that the default PRNG does converge towards Pi when doing a Monte Carlo |
| 6 // simulation. | 6 // simulation. |
| 7 | 7 |
| 8 // Library tag to allow Dartium to run the test. | 8 // Library tag to allow Dartium to run the test. |
| 9 library pi_test; | 9 library pi_test; |
| 10 | 10 |
| 11 import "package:expect/expect.dart"; | 11 import "package:expect/expect.dart"; |
| 12 import 'dart:math'; | 12 import 'dart:math'; |
| 13 | 13 |
| 14 var known_bad_seeds = const [ | 14 var known_bad_seeds = const [50051, 55597, 59208]; |
| 15 50051, | |
| 16 55597, | |
| 17 59208 | |
| 18 ]; | |
| 19 | 15 |
| 20 void main([args]) { | 16 void main([args]) { |
| 21 // Select a seed either from the argument passed in or | 17 // Select a seed either from the argument passed in or |
| 22 // otherwise a random seed. | 18 // otherwise a random seed. |
| 23 var seed = -1; | 19 var seed = -1; |
| 24 if ((args != null) && (args.length > 0)) { | 20 if ((args != null) && (args.length > 0)) { |
| 25 seed = int.parse(args[0]); | 21 seed = int.parse(args[0]); |
| 26 } else { | 22 } else { |
| 27 var seed_prng = new Random(); | 23 var seed_prng = new Random(); |
| 28 while (seed == -1) { | 24 while (seed == -1) { |
| 29 seed = seed_prng.nextInt(1<<16); | 25 seed = seed_prng.nextInt(1 << 16); |
| 30 if (known_bad_seeds.contains(seed)) { | 26 if (known_bad_seeds.contains(seed)) { |
| 31 // Reset seed and try again. | 27 // Reset seed and try again. |
| 32 seed = -1; | 28 seed = -1; |
| 33 } | 29 } |
| 34 } | 30 } |
| 35 } | 31 } |
| 36 | 32 |
| 37 // Setup the PRNG for the Monte Carlo simulation. | 33 // Setup the PRNG for the Monte Carlo simulation. |
| 38 print("pi_test seed: $seed"); | 34 print("pi_test seed: $seed"); |
| 39 var prng = new Random(seed); | 35 var prng = new Random(seed); |
| 40 | 36 |
| 41 var outside = 0; | 37 var outside = 0; |
| 42 var inside = 0; | 38 var inside = 0; |
| 43 for (var i = 0; i < 600000; i++) { | 39 for (var i = 0; i < 600000; i++) { |
| 44 var x = prng.nextDouble(); | 40 var x = prng.nextDouble(); |
| 45 var y = prng.nextDouble(); | 41 var y = prng.nextDouble(); |
| 46 if ((x*x) + (y*y) < 1.0) { | 42 if ((x * x) + (y * y) < 1.0) { |
| 47 inside++; | 43 inside++; |
| 48 } else { | 44 } else { |
| 49 outside++; | 45 outside++; |
| 50 } | 46 } |
| 51 } | 47 } |
| 52 // Mmmmh, Pie! | 48 // Mmmmh, Pie! |
| 53 var pie = 4.0 * (inside/(inside + outside)); | 49 var pie = 4.0 * (inside / (inside + outside)); |
| 54 print("$pie"); | 50 print("$pie"); |
| 55 Expect.isTrue(((PI - 0.009) < pie) && (pie < (PI + 0.009))); | 51 Expect.isTrue(((PI - 0.009) < pie) && (pie < (PI + 0.009))); |
| 56 } | 52 } |
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