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