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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
commit | 0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d (patch) | |
tree | a31f07c9bcca9d56ce61e9a1ffd30ef350d513aa /mfbt/tests/TestXorShift128PlusRNG.cpp | |
parent | Initial commit. (diff) | |
download | firefox-esr-0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d.tar.xz firefox-esr-0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d.zip |
Adding upstream version 115.8.0esr.upstream/115.8.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'mfbt/tests/TestXorShift128PlusRNG.cpp')
-rw-r--r-- | mfbt/tests/TestXorShift128PlusRNG.cpp | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/mfbt/tests/TestXorShift128PlusRNG.cpp b/mfbt/tests/TestXorShift128PlusRNG.cpp new file mode 100644 index 0000000000..12b3c547ac --- /dev/null +++ b/mfbt/tests/TestXorShift128PlusRNG.cpp @@ -0,0 +1,101 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this file, + * You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include <math.h> + +#include "mozilla/Assertions.h" +#include "mozilla/PodOperations.h" +#include "mozilla/XorShift128PlusRNG.h" + +using mozilla::non_crypto::XorShift128PlusRNG; + +static void TestDumbSequence() { + XorShift128PlusRNG rng(1, 4); + + // Calculated by hand following the algorithm given in the paper. The upper + // bits are mostly zero because we started with a poor seed; once it has run + // for a while, we'll get an even mix of ones and zeros in all 64 bits. + MOZ_RELEASE_ASSERT(rng.next() == 0x800049); + MOZ_RELEASE_ASSERT(rng.next() == 0x3000186); + MOZ_RELEASE_ASSERT(rng.next() == 0x400003001145); + + // Using ldexp here lets us write out the mantissa in hex, so we can compare + // them with the results generated by hand. + MOZ_RELEASE_ASSERT(rng.nextDouble() == + ldexp(static_cast<double>(0x1400003105049), -53)); + MOZ_RELEASE_ASSERT(rng.nextDouble() == + ldexp(static_cast<double>(0x2000802e49146), -53)); + MOZ_RELEASE_ASSERT(rng.nextDouble() == + ldexp(static_cast<double>(0x248300468544d), -53)); +} + +static size_t Population(uint64_t n) { + size_t pop = 0; + + while (n > 0) { + n &= n - 1; // Clear the rightmost 1-bit in n. + pop++; + } + + return pop; +} + +static void TestPopulation() { + XorShift128PlusRNG rng(698079309544035222ULL, 6012389156611637584ULL); + + // Give it some time to warm up; it should tend towards more + // even distributions of zeros and ones. + for (size_t i = 0; i < 40; i++) rng.next(); + + for (size_t i = 0; i < 40; i++) { + size_t pop = Population(rng.next()); + MOZ_RELEASE_ASSERT(24 <= pop && pop <= 40); + } +} + +static void TestSetState() { + static const uint64_t seed[2] = {1795644156779822404ULL, + 14162896116325912595ULL}; + XorShift128PlusRNG rng(seed[0], seed[1]); + + const size_t n = 10; + uint64_t log[n]; + + for (size_t i = 0; i < n; i++) log[i] = rng.next(); + + rng.setState(seed[0], seed[1]); + + for (size_t i = 0; i < n; i++) MOZ_RELEASE_ASSERT(log[i] == rng.next()); +} + +static void TestDoubleDistribution() { + XorShift128PlusRNG rng(0xa207aaede6859736, 0xaca6ca5060804791); + + const size_t n = 100; + size_t bins[n]; + mozilla::PodArrayZero(bins); + + // This entire file runs in 0.006s on my laptop. Generating + // more numbers lets us put tighter bounds on the bins. + for (size_t i = 0; i < 100000; i++) { + double d = rng.nextDouble(); + MOZ_RELEASE_ASSERT(0.0 <= d && d < 1.0); + bins[(int)(d * n)]++; + } + + for (size_t i = 0; i < n; i++) { + MOZ_RELEASE_ASSERT(900 <= bins[i] && bins[i] <= 1100); + } +} + +int main() { + TestDumbSequence(); + TestPopulation(); + TestSetState(); + TestDoubleDistribution(); + + return 0; +} |