// 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 && kExpectedAverage - kAllowedVariance < cumulative_average && cumulative_average < 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, " #if !defined(NDEBUG) << " (debugging version)"; #else ; #endif }