| // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "butil/rand_util.h" |
| #include "butil/fast_rand.h" |
| #include "butil/time.h" |
| #include <algorithm> |
| #include <limits> |
| |
| #include "butil/logging.h" |
| #include "butil/memory/scoped_ptr.h" |
| #include "butil/time/time.h" |
| #include <gtest/gtest.h> |
| |
| namespace { |
| |
| const int kIntMin = std::numeric_limits<int>::min(); |
| const int kIntMax = std::numeric_limits<int>::max(); |
| |
| } // namespace |
| |
| TEST(RandUtilTest, Sanity) { |
| EXPECT_EQ(butil::RandInt(0, 0), 0); |
| EXPECT_EQ(butil::RandInt(kIntMin, kIntMin), kIntMin); |
| EXPECT_EQ(butil::RandInt(kIntMax, kIntMax), kIntMax); |
| |
| for (int i = 0; i < 10; ++i) { |
| uint64_t value = butil::fast_rand_in( |
| (uint64_t)0, std::numeric_limits<uint64_t>::max()); |
| if (value != std::numeric_limits<uint64_t>::min() && |
| value != std::numeric_limits<uint64_t>::max()) { |
| break; |
| } else { |
| EXPECT_NE(9, i) << "Never meet random except min/max of uint64"; |
| } |
| } |
| for (int i = 0; i < 10; ++i) { |
| int64_t value = butil::fast_rand_in( |
| std::numeric_limits<int64_t>::min(), |
| std::numeric_limits<int64_t>::max()); |
| if (value != std::numeric_limits<int64_t>::min() && |
| value != std::numeric_limits<int64_t>::max()) { |
| break; |
| } else { |
| EXPECT_NE(9, i) << "Never meet random except min/max of int64"; |
| } |
| } |
| EXPECT_EQ(butil::fast_rand_in(-1, -1), -1); |
| EXPECT_EQ(butil::fast_rand_in(1, 1), 1); |
| EXPECT_EQ(butil::fast_rand_in(0, 0), 0); |
| EXPECT_EQ(butil::fast_rand_in(std::numeric_limits<int64_t>::min(), |
| std::numeric_limits<int64_t>::min()), |
| std::numeric_limits<int64_t>::min()); |
| EXPECT_EQ(butil::fast_rand_in(std::numeric_limits<int64_t>::max(), |
| std::numeric_limits<int64_t>::max()), |
| std::numeric_limits<int64_t>::max()); |
| EXPECT_EQ(butil::fast_rand_in(std::numeric_limits<uint64_t>::min(), |
| std::numeric_limits<uint64_t>::min()), |
| std::numeric_limits<uint64_t>::min()); |
| EXPECT_EQ(butil::fast_rand_in(std::numeric_limits<uint64_t>::max(), |
| std::numeric_limits<uint64_t>::max()), |
| std::numeric_limits<uint64_t>::max()); |
| } |
| |
| TEST(RandUtilTest, RandDouble) { |
| // Force 64-bit precision, making sure we're not in a 80-bit FPU register. |
| volatile double number = butil::RandDouble(); |
| EXPECT_GT(1.0, number); |
| EXPECT_LE(0.0, number); |
| |
| volatile double number2 = butil::fast_rand_double(); |
| EXPECT_GT(1.0, number2); |
| EXPECT_LE(0.0, number2); |
| } |
| |
| TEST(RandUtilTest, RandBytes) { |
| const size_t buffer_size = 50; |
| char buffer[buffer_size]; |
| memset(buffer, 0, buffer_size); |
| butil::RandBytes(buffer, buffer_size); |
| std::sort(buffer, buffer + buffer_size); |
| // Probability of occurrence of less than 25 unique bytes in 50 random bytes |
| // is below 10^-25. |
| EXPECT_GT(std::unique(buffer, buffer + buffer_size) - buffer, 25); |
| } |
| |
| TEST(RandUtilTest, RandBytesAsString) { |
| std::string random_string = butil::RandBytesAsString(1); |
| EXPECT_EQ(1U, random_string.size()); |
| random_string = butil::RandBytesAsString(145); |
| EXPECT_EQ(145U, random_string.size()); |
| char accumulator = 0; |
| for (size_t i = 0; i < random_string.size(); ++i) { |
| accumulator |= random_string[i]; |
| } |
| // In theory this test can fail, but it won't before the universe dies of |
| // heat death. |
| EXPECT_NE(0, accumulator); |
| } |
| |
| // Make sure that it is still appropriate to use RandGenerator in conjunction |
| // with std::random_shuffle(). |
| TEST(RandUtilTest, RandGeneratorForRandomShuffle) { |
| EXPECT_EQ(butil::RandGenerator(1), 0U); |
| EXPECT_LE(std::numeric_limits<ptrdiff_t>::max(), |
| std::numeric_limits<int64_t>::max()); |
| } |
| |
| TEST(RandUtilTest, RandGeneratorIsUniform) { |
| // Verify that RandGenerator has a uniform distribution. This is a |
| // regression test that consistently failed when RandGenerator was |
| // implemented this way: |
| // |
| // return butil::RandUint64() % max; |
| // |
| // A degenerate case for such an implementation is e.g. a top of |
| // range that is 2/3rds of the way to MAX_UINT64, in which case the |
| // bottom half of the range would be twice as likely to occur as the |
| // top half. A bit of calculus care of jar@ shows that the largest |
| // measurable delta is when the top of the range is 3/4ths of the |
| // way, so that's what we use in the test. |
| const uint64_t kTopOfRange = (std::numeric_limits<uint64_t>::max() / 4ULL) * 3ULL; |
| const uint64_t kExpectedAverage = kTopOfRange / 2ULL; |
| const uint64_t kAllowedVariance = kExpectedAverage / 50ULL; // +/- 2% |
| const int kMinAttempts = 1000; |
| const int kMaxAttempts = 1000000; |
| |
| for (int round = 0; round < 2; ++round) { |
| LOG(INFO) << "Use " << (round == 0 ? "RandUtil" : "fast_rand"); |
| double cumulative_average = 0.0; |
| int count = 0; |
| while (count < kMaxAttempts) { |
| uint64_t value = (round == 0 ? butil::RandGenerator(kTopOfRange) |
| : butil::fast_rand_less_than(kTopOfRange)); |
| cumulative_average = (count * cumulative_average + value) / (count + 1); |
| |
| // Don't quit too quickly for things to start converging, or we may have |
| // a false positive. |
| if (count > kMinAttempts && |
| double(kExpectedAverage - kAllowedVariance) < cumulative_average && |
| cumulative_average < double(kExpectedAverage + kAllowedVariance)) { |
| break; |
| } |
| |
| ++count; |
| } |
| |
| ASSERT_LT(count, kMaxAttempts) << "Expected average was " << |
| kExpectedAverage << ", average ended at " << cumulative_average; |
| } |
| } |
| |
| TEST(RandUtilTest, RandUint64ProducesBothValuesOfAllBits) { |
| // This tests to see that our underlying random generator is good |
| // enough, for some value of good enough. |
| const uint64_t kAllZeros = 0ULL; |
| const uint64_t kAllOnes = ~kAllZeros; |
| |
| for (int round = 0; round < 2; ++round) { |
| LOG(INFO) << "Use " << (round == 0 ? "RandUtil" : "fast_rand"); |
| uint64_t found_ones = kAllZeros; |
| uint64_t found_zeros = kAllOnes; |
| bool fail = true; |
| for (size_t i = 0; i < 1000; ++i) { |
| uint64_t value = (round == 0 ? butil::RandUint64() : butil::fast_rand()); |
| found_ones |= value; |
| found_zeros &= value; |
| |
| if (found_zeros == kAllZeros && found_ones == kAllOnes) { |
| fail = false; |
| break; |
| } |
| } |
| if (fail) { |
| FAIL() << "Didn't achieve all bit values in maximum number of tries."; |
| } |
| } |
| } |
| |
| // Benchmark test for RandBytes(). Disabled since it's intentionally slow and |
| // does not test anything that isn't already tested by the existing RandBytes() |
| // tests. |
| TEST(RandUtilTest, DISABLED_RandBytesPerf) { |
| // Benchmark the performance of |kTestIterations| of RandBytes() using a |
| // buffer size of |kTestBufferSize|. |
| const int kTestIterations = 10; |
| const size_t kTestBufferSize = 1 * 1024 * 1024; |
| |
| scoped_ptr<uint8_t[]> buffer(new uint8_t[kTestBufferSize]); |
| const butil::TimeTicks now = butil::TimeTicks::HighResNow(); |
| for (int i = 0; i < kTestIterations; ++i) { |
| butil::RandBytes(buffer.get(), kTestBufferSize); |
| } |
| const butil::TimeTicks end = butil::TimeTicks::HighResNow(); |
| |
| LOG(INFO) << "RandBytes(" << kTestBufferSize << ") took: " |
| << (end - now).InMicroseconds() << "ms"; |
| } |
| |
| TEST(RandUtilTest, fast_rand_perf) { |
| const int kTestIterations = 1000000; |
| const int kRange = 17; |
| uint64_t s = 0; |
| butil::Timer tm; |
| tm.start(); |
| for (int i = 0; i < kTestIterations; ++i) { |
| s += butil::fast_rand_less_than(kRange); |
| } |
| tm.stop(); |
| LOG(INFO) << "Each fast_rand_less_than took " << tm.n_elapsed() / kTestIterations |
| << " ns, s=" << s |
| #if !defined(NDEBUG) |
| << " (debugging version)"; |
| #else |
| ; |
| #endif |
| } |