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Diffstat (limited to 'webrtc/base/random_unittest.cc')
| -rw-r--r-- | webrtc/base/random_unittest.cc | 302 |
1 files changed, 302 insertions, 0 deletions
diff --git a/webrtc/base/random_unittest.cc b/webrtc/base/random_unittest.cc new file mode 100644 index 0000000000..febae1c28f --- /dev/null +++ b/webrtc/base/random_unittest.cc @@ -0,0 +1,302 @@ +/* + * Copyright (c) 2015 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#include <math.h> + +#include <limits> +#include <vector> + +#include "testing/gtest/include/gtest/gtest.h" +#include "webrtc/base/random.h" + +namespace webrtc { + +namespace { +// Computes the positive remainder of x/n. +template <typename T> +T fdiv_remainder(T x, T n) { + RTC_CHECK_GE(n, static_cast<T>(0)); + T remainder = x % n; + if (remainder < 0) + remainder += n; + return remainder; +} +} // namespace + +// Sample a number of random integers of type T. Divide them into buckets +// based on the remainder when dividing by bucket_count and check that each +// bucket gets roughly the expected number of elements. +template <typename T> +void UniformBucketTest(T bucket_count, int samples, Random* prng) { + std::vector<int> buckets(bucket_count, 0); + + uint64_t total_values = 1ull << (std::numeric_limits<T>::digits + + std::numeric_limits<T>::is_signed); + T upper_limit = + std::numeric_limits<T>::max() - + static_cast<T>(total_values % static_cast<uint64_t>(bucket_count)); + ASSERT_GT(upper_limit, std::numeric_limits<T>::max() / 2); + + for (int i = 0; i < samples; i++) { + T sample; + do { + // We exclude a few numbers from the range so that it is divisible by + // the number of buckets. If we are unlucky and hit one of the excluded + // numbers we just resample. Note that if the number of buckets is a + // power of 2, then we don't have to exclude anything. + sample = prng->Rand<T>(); + } while (sample > upper_limit); + buckets[fdiv_remainder(sample, bucket_count)]++; + } + + for (T i = 0; i < bucket_count; i++) { + // Expect the result to be within 3 standard deviations of the mean. + EXPECT_NEAR(buckets[i], samples / bucket_count, + 3 * sqrt(samples / bucket_count)); + } +} + +TEST(RandomNumberGeneratorTest, BucketTestSignedChar) { + Random prng(7297352569824ull); + UniformBucketTest<signed char>(64, 640000, &prng); + UniformBucketTest<signed char>(11, 440000, &prng); + UniformBucketTest<signed char>(3, 270000, &prng); +} + +TEST(RandomNumberGeneratorTest, BucketTestUnsignedChar) { + Random prng(7297352569824ull); + UniformBucketTest<unsigned char>(64, 640000, &prng); + UniformBucketTest<unsigned char>(11, 440000, &prng); + UniformBucketTest<unsigned char>(3, 270000, &prng); +} + +TEST(RandomNumberGeneratorTest, BucketTestSignedShort) { + Random prng(7297352569824ull); + UniformBucketTest<int16_t>(64, 640000, &prng); + UniformBucketTest<int16_t>(11, 440000, &prng); + UniformBucketTest<int16_t>(3, 270000, &prng); +} + +TEST(RandomNumberGeneratorTest, BucketTestUnsignedShort) { + Random prng(7297352569824ull); + UniformBucketTest<uint16_t>(64, 640000, &prng); + UniformBucketTest<uint16_t>(11, 440000, &prng); + UniformBucketTest<uint16_t>(3, 270000, &prng); +} + +TEST(RandomNumberGeneratorTest, BucketTestSignedInt) { + Random prng(7297352569824ull); + UniformBucketTest<signed int>(64, 640000, &prng); + UniformBucketTest<signed int>(11, 440000, &prng); + UniformBucketTest<signed int>(3, 270000, &prng); +} + +TEST(RandomNumberGeneratorTest, BucketTestUnsignedInt) { + Random prng(7297352569824ull); + UniformBucketTest<unsigned int>(64, 640000, &prng); + UniformBucketTest<unsigned int>(11, 440000, &prng); + UniformBucketTest<unsigned int>(3, 270000, &prng); +} + +// The range of the random numbers is divided into bucket_count intervals +// of consecutive numbers. Check that approximately equally many numbers +// from each inteval are generated. +void BucketTestSignedInterval(unsigned int bucket_count, + unsigned int samples, + int32_t low, + int32_t high, + int sigma_level, + Random* prng) { + std::vector<unsigned int> buckets(bucket_count, 0); + + ASSERT_GE(high, low); + ASSERT_GE(bucket_count, 2u); + uint32_t interval = static_cast<uint32_t>(high - low + 1); + uint32_t numbers_per_bucket; + if (interval == 0) { + // The computation high - low + 1 should be 2^32 but overflowed + // Hence, bucket_count must be a power of 2 + ASSERT_EQ(bucket_count & (bucket_count - 1), 0u); + numbers_per_bucket = (0x80000000u / bucket_count) * 2; + } else { + ASSERT_EQ(interval % bucket_count, 0u); + numbers_per_bucket = interval / bucket_count; + } + + for (unsigned int i = 0; i < samples; i++) { + int32_t sample = prng->Rand(low, high); + EXPECT_LE(low, sample); + EXPECT_GE(high, sample); + buckets[static_cast<uint32_t>(sample - low) / numbers_per_bucket]++; + } + + for (unsigned int i = 0; i < bucket_count; i++) { + // Expect the result to be within 3 standard deviations of the mean, + // or more generally, within sigma_level standard deviations of the mean. + double mean = static_cast<double>(samples) / bucket_count; + EXPECT_NEAR(buckets[i], mean, sigma_level * sqrt(mean)); + } +} + +// The range of the random numbers is divided into bucket_count intervals +// of consecutive numbers. Check that approximately equally many numbers +// from each inteval are generated. +void BucketTestUnsignedInterval(unsigned int bucket_count, + unsigned int samples, + uint32_t low, + uint32_t high, + int sigma_level, + Random* prng) { + std::vector<unsigned int> buckets(bucket_count, 0); + + ASSERT_GE(high, low); + ASSERT_GE(bucket_count, 2u); + uint32_t interval = static_cast<uint32_t>(high - low + 1); + uint32_t numbers_per_bucket; + if (interval == 0) { + // The computation high - low + 1 should be 2^32 but overflowed + // Hence, bucket_count must be a power of 2 + ASSERT_EQ(bucket_count & (bucket_count - 1), 0u); + numbers_per_bucket = (0x80000000u / bucket_count) * 2; + } else { + ASSERT_EQ(interval % bucket_count, 0u); + numbers_per_bucket = interval / bucket_count; + } + + for (unsigned int i = 0; i < samples; i++) { + uint32_t sample = prng->Rand(low, high); + EXPECT_LE(low, sample); + EXPECT_GE(high, sample); + buckets[static_cast<uint32_t>(sample - low) / numbers_per_bucket]++; + } + + for (unsigned int i = 0; i < bucket_count; i++) { + // Expect the result to be within 3 standard deviations of the mean, + // or more generally, within sigma_level standard deviations of the mean. + double mean = static_cast<double>(samples) / bucket_count; + EXPECT_NEAR(buckets[i], mean, sigma_level * sqrt(mean)); + } +} + +TEST(RandomNumberGeneratorTest, UniformUnsignedInterval) { + Random prng(299792458ull); + BucketTestUnsignedInterval(2, 100000, 0, 1, 3, &prng); + BucketTestUnsignedInterval(7, 100000, 1, 14, 3, &prng); + BucketTestUnsignedInterval(11, 100000, 1000, 1010, 3, &prng); + BucketTestUnsignedInterval(100, 100000, 0, 99, 3, &prng); + BucketTestUnsignedInterval(2, 100000, 0, 4294967295, 3, &prng); + BucketTestUnsignedInterval(17, 100000, 455, 2147484110, 3, &prng); + // 99.7% of all samples will be within 3 standard deviations of the mean, + // but since we test 1000 buckets we allow an interval of 4 sigma. + BucketTestUnsignedInterval(1000, 1000000, 0, 2147483999, 4, &prng); +} + +TEST(RandomNumberGeneratorTest, UniformSignedInterval) { + Random prng(66260695729ull); + BucketTestSignedInterval(2, 100000, 0, 1, 3, &prng); + BucketTestSignedInterval(7, 100000, -2, 4, 3, &prng); + BucketTestSignedInterval(11, 100000, 1000, 1010, 3, &prng); + BucketTestSignedInterval(100, 100000, 0, 99, 3, &prng); + BucketTestSignedInterval(2, 100000, std::numeric_limits<int32_t>::min(), + std::numeric_limits<int32_t>::max(), 3, &prng); + BucketTestSignedInterval(17, 100000, -1073741826, 1073741829, 3, &prng); + // 99.7% of all samples will be within 3 standard deviations of the mean, + // but since we test 1000 buckets we allow an interval of 4 sigma. + BucketTestSignedInterval(1000, 1000000, -352, 2147483647, 4, &prng); +} + +// The range of the random numbers is divided into bucket_count intervals +// of consecutive numbers. Check that approximately equally many numbers +// from each inteval are generated. +void BucketTestFloat(unsigned int bucket_count, + unsigned int samples, + int sigma_level, + Random* prng) { + ASSERT_GE(bucket_count, 2u); + std::vector<unsigned int> buckets(bucket_count, 0); + + for (unsigned int i = 0; i < samples; i++) { + uint32_t sample = bucket_count * prng->Rand<float>(); + EXPECT_LE(0u, sample); + EXPECT_GE(bucket_count - 1, sample); + buckets[sample]++; + } + + for (unsigned int i = 0; i < bucket_count; i++) { + // Expect the result to be within 3 standard deviations of the mean, + // or more generally, within sigma_level standard deviations of the mean. + double mean = static_cast<double>(samples) / bucket_count; + EXPECT_NEAR(buckets[i], mean, sigma_level * sqrt(mean)); + } +} + +TEST(RandomNumberGeneratorTest, UniformFloatInterval) { + Random prng(1380648813ull); + BucketTestFloat(100, 100000, 3, &prng); + // 99.7% of all samples will be within 3 standard deviations of the mean, + // but since we test 1000 buckets we allow an interval of 4 sigma. + // BucketTestSignedInterval(1000, 1000000, -352, 2147483647, 4, &prng); +} + +TEST(RandomNumberGeneratorTest, SignedHasSameBitPattern) { + Random prng_signed(66738480ull), prng_unsigned(66738480ull); + + for (int i = 0; i < 1000; i++) { + signed int s = prng_signed.Rand<signed int>(); + unsigned int u = prng_unsigned.Rand<unsigned int>(); + EXPECT_EQ(u, static_cast<unsigned int>(s)); + } + + for (int i = 0; i < 1000; i++) { + int16_t s = prng_signed.Rand<int16_t>(); + uint16_t u = prng_unsigned.Rand<uint16_t>(); + EXPECT_EQ(u, static_cast<uint16_t>(s)); + } + + for (int i = 0; i < 1000; i++) { + signed char s = prng_signed.Rand<signed char>(); + unsigned char u = prng_unsigned.Rand<unsigned char>(); + EXPECT_EQ(u, static_cast<unsigned char>(s)); + } +} + +TEST(RandomNumberGeneratorTest, Gaussian) { + const int kN = 100000; + const int kBuckets = 100; + const double kMean = 49; + const double kStddev = 10; + + Random prng(1256637061); + + std::vector<unsigned int> buckets(kBuckets, 0); + for (int i = 0; i < kN; i++) { + int index = prng.Gaussian(kMean, kStddev) + 0.5; + if (index >= 0 && index < kBuckets) { + buckets[index]++; + } + } + + const double kPi = 3.14159265358979323846; + const double kScale = 1 / (kStddev * sqrt(2.0 * kPi)); + const double kDiv = -2.0 * kStddev * kStddev; + for (int n = 0; n < kBuckets; ++n) { + // Use Simpsons rule to estimate the probability that a random gaussian + // sample is in the interval [n-0.5, n+0.5]. + double f_left = kScale * exp((n - kMean - 0.5) * (n - kMean - 0.5) / kDiv); + double f_mid = kScale * exp((n - kMean) * (n - kMean) / kDiv); + double f_right = kScale * exp((n - kMean + 0.5) * (n - kMean + 0.5) / kDiv); + double normal_dist = (f_left + 4 * f_mid + f_right) / 6; + // Expect the number of samples to be within 3 standard deviations + // (rounded up) of the expected number of samples in the bucket. + EXPECT_NEAR(buckets[n], kN * normal_dist, 3 * sqrt(kN * normal_dist) + 1); + } +} + +} // namespace webrtc |