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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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