lrn@google.com
d63af4cdc8
This changes the sequences generated by Random for a given seed,
since the internal state will not be the same as for the unmixed
seed.
It is consistent between VM and dart2js.
The provided integer seed is hashed as follows:
uint64 hash = 0;
while (seed > 0) {
hash = hash * 1037 + mix64((int64)seed);
seed >>= 64;
}
where mix64 mixes the bits of a 64-bit value.
The hash is used to initialize the random generator's internal state.
R=floitsch@google.com, iposva@google.com
Review URL: https://codereview.chromium.org//156533002
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@32412 260f80e4-7a28-3924-810f-c04153c831b5
102 lines
4.4 KiB
Dart
102 lines
4.4 KiB
Dart
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// Test that rnd.nextInt with a seed generates the same sequence each time.
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// Library tag to allow Dartium to run the test.
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library random_test;
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import "package:expect/expect.dart";
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import 'dart:math';
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main() {
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checkSequence();
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checkSeed();
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}
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void checkSequence() {
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// Check the sequence of numbers generated by the random generator for a seed
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// doesn't change unintendedly, and it agrees between implementations.
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var rnd = new Random(20130307);
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// Make sure we do not break the random number generation.
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// If the random algorithm changes, make sure both the VM and dart2js
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// generate the same new sequence.
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var i = 1;
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Expect.equals( 0, rnd.nextInt(i *= 2));
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Expect.equals( 3, rnd.nextInt(i *= 2));
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Expect.equals( 7, rnd.nextInt(i *= 2));
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Expect.equals( 5, rnd.nextInt(i *= 2));
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Expect.equals( 29, rnd.nextInt(i *= 2));
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Expect.equals( 17, rnd.nextInt(i *= 2));
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Expect.equals( 104, rnd.nextInt(i *= 2));
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Expect.equals( 199, rnd.nextInt(i *= 2));
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Expect.equals( 408, rnd.nextInt(i *= 2));
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Expect.equals( 362, rnd.nextInt(i *= 2));
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Expect.equals( 995, rnd.nextInt(i *= 2));
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Expect.equals( 2561, rnd.nextInt(i *= 2));
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Expect.equals( 2548, rnd.nextInt(i *= 2));
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Expect.equals( 9553, rnd.nextInt(i *= 2));
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Expect.equals( 2628, rnd.nextInt(i *= 2));
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Expect.equals( 42376, rnd.nextInt(i *= 2));
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Expect.equals( 101848, rnd.nextInt(i *= 2));
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Expect.equals( 85153, rnd.nextInt(i *= 2));
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Expect.equals( 495595, rnd.nextInt(i *= 2));
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Expect.equals( 647122, rnd.nextInt(i *= 2));
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Expect.equals( 793546, rnd.nextInt(i *= 2));
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Expect.equals( 1073343, rnd.nextInt(i *= 2));
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Expect.equals( 4479969, rnd.nextInt(i *= 2));
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Expect.equals( 9680425, rnd.nextInt(i *= 2));
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Expect.equals( 28460171, rnd.nextInt(i *= 2));
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Expect.equals( 49481738, rnd.nextInt(i *= 2));
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Expect.equals( 9878974, rnd.nextInt(i *= 2));
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Expect.equals( 132552472, rnd.nextInt(i *= 2));
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Expect.equals( 210267283, rnd.nextInt(i *= 2));
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Expect.equals( 125422442, rnd.nextInt(i *= 2));
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Expect.equals( 226275094, rnd.nextInt(i *= 2));
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Expect.equals(1639629168, rnd.nextInt(i *= 2));
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Expect.equals(0x100000000, i);
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// If max is too large expect an ArgumentError.
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Expect.throws(() => rnd.nextInt(i + 1), (e) => e is ArgumentError);
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rnd = new Random(6790);
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Expect.approxEquals(0.1202733131, rnd.nextDouble());
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Expect.approxEquals(0.5554054805, rnd.nextDouble());
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Expect.approxEquals(0.0385160727, rnd.nextDouble());
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Expect.approxEquals(0.2836345217, rnd.nextDouble());
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}
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void checkSeed() {
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// Check that various seeds generate the expected first values.
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// 53 significant bits, so the number is representable in JS.
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var rawSeed = 0x19a32c640e1d71;
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var expectations = [
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26007, 43006, 46458, 18610, 16413, 50455, 2164, 47399, 8859, 9732,
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20367, 33935, 54549, 54913, 4819, 24198, 49353, 22277, 51852, 35959,
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45347, 12100, 10136, 22372, 15293, 20066, 1351, 49030, 64845, 12793,
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50916, 55784, 43170, 27653, 34696, 1492, 50255, 9597, 45929, 2874,
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27629, 53084, 36064, 42140, 32016, 41751, 13967, 20516, 578, 16773,
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53064, 14814, 22737, 48846, 45147, 10205, 56584, 63711, 44128, 21099,
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47966, 35471, 39576, 1141, 45716, 54940, 57406, 15437, 31721, 35044,
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28136, 39797, 50801, 22184, 58686
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];
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var negative_seed_expectations = [
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12170, 42844, 39228, 64032, 29046, 57572, 8453, 52224, 27060, 28454,
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20510, 28804, 59221, 53422, 11047, 50864, 33997, 19611, 1250, 65088,
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19690, 11396, 20, 48867, 44862, 47129, 58724, 13325, 50005, 33320,
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16523, 4740, 63721, 63272, 30545, 51403, 35845, 3943, 31850, 23148,
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26307, 1724, 29281, 39988, 43653, 48012, 43810, 16755, 13105, 25325,
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32648, 19958, 38838, 8322, 3421, 28624, 17269, 45385, 50680, 1696,
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26088, 2787, 48566, 34357, 27731, 51764, 8455, 16498, 59721, 59568,
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46333, 7935, 51459, 36766, 50711
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];
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for (var i = 0, m = 1; i < 75; i++) {
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Expect.equals(expectations[i], new Random(rawSeed * m).nextInt(65536));
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Expect.equals(negative_seed_expectations[i],
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new Random(rawSeed * -m).nextInt(65536));
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m *= 2;
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}
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// And test zero seed too.
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Expect.equals(21391, new Random(0).nextInt(65536));
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}
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