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// Copyright 2007 Google Inc.
// Authors: Jeff Dean, Lincoln Smith
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <config.h>
#include "rolling_hash.h"
#include <stdint.h> // uint32_t
#include <stdlib.h> // rand, srand
#include <vector>
#include "testing.h"
namespace open_vcdiff {
namespace {
static const uint32_t kBase = RollingHashUtil::kBase;
class RollingHashSimpleTest : public testing::Test {
protected:
RollingHashSimpleTest() { }
virtual ~RollingHashSimpleTest() { }
void TestModBase(uint32_t operand) {
EXPECT_EQ(operand % kBase, RollingHashUtil::ModBase(operand));
EXPECT_EQ(static_cast<uint32_t>((-static_cast<int32_t>(operand)) % kBase),
RollingHashUtil::FindModBaseInverse(operand));
EXPECT_EQ(0U, RollingHashUtil::ModBase(
operand + RollingHashUtil::FindModBaseInverse(operand)));
}
void TestHashFirstTwoBytes(char first_value, char second_value) {
char buf[2];
buf[0] = first_value;
buf[1] = second_value;
EXPECT_EQ(RollingHashUtil::HashFirstTwoBytes(buf),
RollingHashUtil::HashStep(RollingHashUtil::HashStep(0,
first_value),
second_value));
EXPECT_EQ(RollingHashUtil::HashFirstTwoBytes(buf),
RollingHashUtil::HashStep(static_cast<unsigned char>(first_value),
second_value));
}
};
#ifdef GTEST_HAS_DEATH_TEST
typedef RollingHashSimpleTest RollingHashDeathTest;
#endif // GTEST_HAS_DEATH_TEST
TEST_F(RollingHashSimpleTest, KBaseIsAPowerOfTwo) {
EXPECT_EQ(0U, kBase & (kBase - 1));
}
TEST_F(RollingHashSimpleTest, TestModBaseForValues) {
TestModBase(0);
TestModBase(10);
TestModBase(static_cast<uint32_t>(-10));
TestModBase(kBase - 1);
TestModBase(kBase);
TestModBase(kBase + 1);
TestModBase(0x7FFFFFFF);
TestModBase(0x80000000);
TestModBase(0xFFFFFFFE);
TestModBase(0xFFFFFFFF);
}
TEST_F(RollingHashSimpleTest, VerifyHashFirstTwoBytes) {
TestHashFirstTwoBytes(0x00, 0x00);
TestHashFirstTwoBytes(0x00, 0xFF);
TestHashFirstTwoBytes(0xFF, 0x00);
TestHashFirstTwoBytes(0xFF, 0xFF);
TestHashFirstTwoBytes(0x00, 0x80);
TestHashFirstTwoBytes(0x7F, 0xFF);
TestHashFirstTwoBytes(0x7F, 0x80);
TestHashFirstTwoBytes(0x01, 0x8F);
}
#ifdef GTEST_HAS_DEATH_TEST
TEST_F(RollingHashDeathTest, InstantiateRollingHashWithoutCallingInit) {
EXPECT_DEBUG_DEATH(RollingHash<16> bad_hash, "Init");
}
#endif // GTEST_HAS_DEATH_TEST
class RollingHashTest : public testing::Test {
public:
static const int kUpdateHashBlocks = 1000;
static const int kLargestBlockSize = 128;
static void MakeRandomBuffer(char* buffer, int buffer_size) {
for (int i = 0; i < buffer_size; ++i) {
buffer[i] = PortableRandomInRange<unsigned char>(0xFF);
}
}
template<int kBlockSize> static void BM_DefaultHash(int iterations,
const char *buffer) {
RollingHash<kBlockSize> hasher;
static uint32_t result_array[kUpdateHashBlocks];
for (int iter = 0; iter < iterations; ++iter) {
for (int i = 0; i < kUpdateHashBlocks; ++i) {
result_array[i] = hasher.Hash(&buffer[i]);
}
}
}
template<int kBlockSize> static void BM_UpdateHash(int iterations,
const char *buffer) {
RollingHash<kBlockSize> hasher;
static uint32_t result_array[kUpdateHashBlocks];
for (int iter = 0; iter < iterations; ++iter) {
uint32_t running_hash = hasher.Hash(buffer);
for (int i = 0; i < kUpdateHashBlocks; ++i) {
running_hash = hasher.UpdateHash(running_hash,
buffer[i],
buffer[i + kBlockSize]);
result_array[i] = running_hash;
}
}
}
protected:
static const int kUpdateHashTestIterations = 400;
static const int kTimingTestSize = 1 << 14; // 16K iterations
RollingHashTest() { }
virtual ~RollingHashTest() { }
template<int kBlockSize> void UpdateHashMatchesHashForBlockSize() {
RollingHash<kBlockSize>::Init();
RollingHash<kBlockSize> hasher;
for (int x = 0; x < kUpdateHashTestIterations; ++x) {
int random_buffer_size =
PortableRandomInRange(kUpdateHashBlocks - 1) + kBlockSize;
MakeRandomBuffer(buffer_, random_buffer_size);
uint32_t running_hash = hasher.Hash(buffer_);
for (int i = kBlockSize; i < random_buffer_size; ++i) {
// UpdateHash() calculates the hash value incrementally.
running_hash = hasher.UpdateHash(running_hash,
buffer_[i - kBlockSize],
buffer_[i]);
// Hash() calculates the hash value from scratch. Verify that both
// methods return the same hash value.
EXPECT_EQ(running_hash, hasher.Hash(&buffer_[i + 1 - kBlockSize]));
}
}
}
template<int kBlockSize> double DefaultHashTimingTest() {
// Execution time is expected to be O(kBlockSize) per hash operation,
// so scale the number of iterations accordingly
const int kTimingTestIterations = kTimingTestSize / kBlockSize;
CycleTimer timer;
timer.Start();
BM_DefaultHash<kBlockSize>(kTimingTestIterations, buffer_);
timer.Stop();
return static_cast<double>(timer.GetInUsec())
/ (kTimingTestIterations * kUpdateHashBlocks);
}
template<int kBlockSize> double RollingTimingTest() {
// Execution time is expected to be O(1) per hash operation,
// so leave the number of iterations constant
const int kTimingTestIterations = kTimingTestSize;
CycleTimer timer;
timer.Start();
BM_UpdateHash<kBlockSize>(kTimingTestIterations, buffer_);
timer.Stop();
return static_cast<double>(timer.GetInUsec())
/ (kTimingTestIterations * kUpdateHashBlocks);
}
double FindPercentage(double original, double modified) {
if (original < 0.0001) {
return 0.0;
} else {
return ((modified - original) / original) * 100.0;
}
}
template<int kBlockSize> void RunTimingTestForBlockSize() {
RollingHash<kBlockSize>::Init();
MakeRandomBuffer(buffer_, sizeof(buffer_));
const double time_for_default_hash = DefaultHashTimingTest<kBlockSize>();
const double time_for_rolling_hash = RollingTimingTest<kBlockSize>();
printf("%d\t%f\t%f (%f%%)\n",
kBlockSize,
time_for_default_hash,
time_for_rolling_hash,
FindPercentage(time_for_default_hash, time_for_rolling_hash));
CHECK_GT(time_for_default_hash, 0.0);
CHECK_GT(time_for_rolling_hash, 0.0);
if (kBlockSize > 16) {
EXPECT_GT(time_for_default_hash, time_for_rolling_hash);
}
}
char buffer_[kUpdateHashBlocks + kLargestBlockSize];
};
TEST_F(RollingHashTest, UpdateHashMatchesHashFromScratch) {
srand(1); // test should be deterministic, including calls to rand()
UpdateHashMatchesHashForBlockSize<4>();
UpdateHashMatchesHashForBlockSize<8>();
UpdateHashMatchesHashForBlockSize<16>();
UpdateHashMatchesHashForBlockSize<32>();
UpdateHashMatchesHashForBlockSize<64>();
UpdateHashMatchesHashForBlockSize<128>();
}
TEST_F(RollingHashTest, TimingTests) {
srand(1); // test should be deterministic, including calls to rand()
printf("BlkSize\tHash (us)\tUpdateHash (us)\n");
RunTimingTestForBlockSize<4>();
RunTimingTestForBlockSize<8>();
RunTimingTestForBlockSize<16>();
RunTimingTestForBlockSize<32>();
RunTimingTestForBlockSize<64>();
RunTimingTestForBlockSize<128>();
}
} // anonymous namespace
} // namespace open_vcdiff
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