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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 &&
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
}