Abseil Common Libraries (C++) (grcp 依赖) https://abseil.io/
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
 

453 lines
14 KiB

// Copyright 2017 The Abseil Authors.
//
// 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 "absl/strings/internal/fastmem.h"
#include <memory>
#include <random>
#include <string>
#include "base/init_google.h"
#include "base/logging.h"
#include "testing/base/public/benchmark.h"
#include "gtest/gtest.h"
namespace {
using RandomEngine = std::minstd_rand0;
void VerifyResults(const int r1, const int r2, const std::string& a,
const std::string& b) {
CHECK_EQ(a.size(), b.size());
if (r1 == 0) {
EXPECT_EQ(r2, 0) << a << " " << b;
} else if (r1 > 0) {
EXPECT_GT(r2, 0) << a << " " << b;
} else {
EXPECT_LT(r2, 0) << a << " " << b;
}
if ((r1 == 0) == (r2 == 0)) {
EXPECT_EQ(r1 == 0,
absl::strings_internal::memeq(a.data(), b.data(), a.size()))
<< r1 << " " << a << " " << b;
}
}
// Check correctness against glibc's memcmp implementation
void CheckSingle(const std::string& a, const std::string& b) {
CHECK_EQ(a.size(), b.size());
const int r1 = memcmp(a.data(), b.data(), a.size());
const int r2 =
absl::strings_internal::fastmemcmp_inlined(a.data(), b.data(), a.size());
VerifyResults(r1, r2, a, b);
}
void GenerateString(size_t len, std::string* s) {
s->clear();
for (int i = 0; i < len; i++) {
*s += ('a' + (i % 26));
}
}
void CheckCompare(const std::string& a, const std::string& b) {
CheckSingle(a, b);
for (int common = 0; common <= 32; common++) {
std::string extra;
GenerateString(common, &extra);
CheckSingle(extra + a, extra + b);
CheckSingle(a + extra, b + extra);
for (char c1 = 'a'; c1 <= 'c'; c1++) {
for (char c2 = 'a'; c2 <= 'c'; c2++) {
CheckSingle(extra + c1 + a, extra + c2 + b);
}
}
}
}
TEST(FastCompare, Misc) {
CheckCompare("", "");
CheckCompare("a", "a");
CheckCompare("ab", "ab");
CheckCompare("abc", "abc");
CheckCompare("abcd", "abcd");
CheckCompare("abcde", "abcde");
CheckCompare("a", "x");
CheckCompare("ab", "xb");
CheckCompare("abc", "xbc");
CheckCompare("abcd", "xbcd");
CheckCompare("abcde", "xbcde");
CheckCompare("x", "a");
CheckCompare("xb", "ab");
CheckCompare("xbc", "abc");
CheckCompare("xbcd", "abcd");
CheckCompare("xbcde", "abcde");
CheckCompare("a", "x");
CheckCompare("ab", "ax");
CheckCompare("abc", "abx");
CheckCompare("abcd", "abcx");
CheckCompare("abcde", "abcdx");
CheckCompare("x", "a");
CheckCompare("ax", "ab");
CheckCompare("abx", "abc");
CheckCompare("abcx", "abcd");
CheckCompare("abcdx", "abcde");
for (int len = 0; len < 1000; len++) {
std::string p(len, 'z');
CheckCompare(p + "x", p + "a");
CheckCompare(p + "ax", p + "ab");
CheckCompare(p + "abx", p + "abc");
CheckCompare(p + "abcx", p + "abcd");
CheckCompare(p + "abcdx", p + "abcde");
}
}
TEST(FastCompare, TrailingByte) {
for (int i = 0; i < 256; i++) {
for (int j = 0; j < 256; j++) {
std::string a(1, i);
std::string b(1, j);
CheckSingle(a, b);
}
}
}
// Check correctness of memcpy_inlined.
void CheckSingleMemcpyInlined(const std::string& a) {
std::unique_ptr<char[]> destination(new char[a.size() + 2]);
destination[0] = 'x';
destination[a.size() + 1] = 'x';
absl::strings_internal::memcpy_inlined(destination.get() + 1, a.data(),
a.size());
CHECK_EQ('x', destination[0]);
CHECK_EQ('x', destination[a.size() + 1]);
CHECK_EQ(0, memcmp(a.data(), destination.get() + 1, a.size()));
}
TEST(MemCpyInlined, Misc) {
CheckSingleMemcpyInlined("");
CheckSingleMemcpyInlined("0");
CheckSingleMemcpyInlined("012");
CheckSingleMemcpyInlined("0123");
CheckSingleMemcpyInlined("01234");
CheckSingleMemcpyInlined("012345");
CheckSingleMemcpyInlined("0123456");
CheckSingleMemcpyInlined("01234567");
CheckSingleMemcpyInlined("012345678");
CheckSingleMemcpyInlined("0123456789");
CheckSingleMemcpyInlined("0123456789a");
CheckSingleMemcpyInlined("0123456789ab");
CheckSingleMemcpyInlined("0123456789abc");
CheckSingleMemcpyInlined("0123456789abcd");
CheckSingleMemcpyInlined("0123456789abcde");
CheckSingleMemcpyInlined("0123456789abcdef");
CheckSingleMemcpyInlined("0123456789abcdefg");
}
template <typename Function>
inline void CopyLoop(benchmark::State& state, int size, Function func) {
char* src = new char[size];
char* dst = new char[size];
memset(src, 'x', size);
memset(dst, 'y', size);
for (auto _ : state) {
func(dst, src, size);
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * size);
CHECK_EQ(dst[0], 'x');
delete[] src;
delete[] dst;
}
void BM_memcpy(benchmark::State& state) {
CopyLoop(state, state.range(0), memcpy);
}
BENCHMARK(BM_memcpy)->DenseRange(1, 18)->Range(32, 8 << 20);
void BM_memcpy_inlined(benchmark::State& state) {
CopyLoop(state, state.range(0), absl::strings_internal::memcpy_inlined);
}
BENCHMARK(BM_memcpy_inlined)->DenseRange(1, 18)->Range(32, 8 << 20);
// unaligned memcpy
void BM_unaligned_memcpy(benchmark::State& state) {
const int n = state.range(0);
const int kMaxOffset = 32;
char* src = new char[n + kMaxOffset];
char* dst = new char[n + kMaxOffset];
memset(src, 'x', n + kMaxOffset);
int r = 0, i = 0;
for (auto _ : state) {
memcpy(dst + (i % kMaxOffset), src + ((i + 5) % kMaxOffset), n);
r += dst[0];
++i;
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * n);
delete[] src;
delete[] dst;
benchmark::DoNotOptimize(r);
}
BENCHMARK(BM_unaligned_memcpy)->DenseRange(1, 18)->Range(32, 8 << 20);
// memmove worst case: heavy overlap, but not always by the same amount.
// Also, the source and destination will often be unaligned.
void BM_memmove_worst_case(benchmark::State& state) {
const int n = state.range(0);
const int32_t kDeterministicSeed = 301;
const int kMaxOffset = 32;
char* src = new char[n + kMaxOffset];
memset(src, 'x', n + kMaxOffset);
size_t offsets[64];
RandomEngine rng(kDeterministicSeed);
std::uniform_int_distribution<size_t> random_to_max_offset(0, kMaxOffset);
for (size_t& offset : offsets) {
offset = random_to_max_offset(rng);
}
int r = 0, i = 0;
for (auto _ : state) {
memmove(src + offsets[i], src + offsets[i + 1], n);
r += src[0];
i = (i + 2) % arraysize(offsets);
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * n);
delete[] src;
benchmark::DoNotOptimize(r);
}
BENCHMARK(BM_memmove_worst_case)->DenseRange(1, 18)->Range(32, 8 << 20);
// memmove cache-friendly: aligned and overlapping with 4k
// between the source and destination addresses.
void BM_memmove_cache_friendly(benchmark::State& state) {
const int n = state.range(0);
char* src = new char[n + 4096];
memset(src, 'x', n);
int r = 0;
while (state.KeepRunningBatch(2)) { // count each memmove as an iteration
memmove(src + 4096, src, n);
memmove(src, src + 4096, n);
r += src[0];
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * n);
delete[] src;
benchmark::DoNotOptimize(r);
}
BENCHMARK(BM_memmove_cache_friendly)
->Arg(5 * 1024)
->Arg(10 * 1024)
->Range(16 << 10, 8 << 20);
// memmove best(?) case: aligned and non-overlapping.
void BM_memmove_aligned_non_overlapping(benchmark::State& state) {
CopyLoop(state, state.range(0), memmove);
}
BENCHMARK(BM_memmove_aligned_non_overlapping)
->DenseRange(1, 18)
->Range(32, 8 << 20);
// memset speed
void BM_memset(benchmark::State& state) {
const int n = state.range(0);
char* dst = new char[n];
int r = 0;
for (auto _ : state) {
memset(dst, 'x', n);
r += dst[0];
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * n);
delete[] dst;
benchmark::DoNotOptimize(r);
}
BENCHMARK(BM_memset)->Range(8, 4096 << 10);
// Bandwidth (vectorization?) test: the ideal generated code will be limited
// by memory bandwidth. Even so-so generated code will max out memory bandwidth
// on some machines.
void BM_membandwidth(benchmark::State& state) {
const int n = state.range(0);
CHECK_EQ(n % 32, 0); // We will read 32 bytes per iter.
char* dst = new char[n];
int r = 0;
for (auto _ : state) {
const uint32_t* p = reinterpret_cast<uint32_t*>(dst);
const uint32_t* limit = reinterpret_cast<uint32_t*>(dst + n);
uint32_t x = 0;
while (p < limit) {
x += p[0];
x += p[1];
x += p[2];
x += p[3];
x += p[4];
x += p[5];
x += p[6];
x += p[7];
p += 8;
}
r += x;
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * n);
delete[] dst;
benchmark::DoNotOptimize(r);
}
BENCHMARK(BM_membandwidth)->Range(32, 16384 << 10);
// Helper for benchmarks. Repeatedly compares two strings that are
// either equal or different only in one character. If test_equal_strings
// is false then position_to_modify determines where the difference will be.
template <typename Function>
ABSL_ATTRIBUTE_ALWAYS_INLINE inline void StringCompareLoop(
benchmark::State& state, bool test_equal_strings,
std::string::size_type position_to_modify, int size, Function func) {
const int kIterMult = 4; // Iteration multiplier for better timing resolution
CHECK_GT(size, 0);
const bool position_to_modify_is_valid =
position_to_modify != std::string::npos && position_to_modify < size;
CHECK_NE(position_to_modify_is_valid, test_equal_strings);
if (!position_to_modify_is_valid) {
position_to_modify = 0;
}
std::string sa(size, 'a');
std::string sb = sa;
char last = sa[size - 1];
int num = 0;
for (auto _ : state) {
for (int i = 0; i < kIterMult; ++i) {
sb[position_to_modify] = test_equal_strings ? last : last ^ 1;
num += func(sa, sb);
}
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * size);
benchmark::DoNotOptimize(num);
}
// Helper for benchmarks. Repeatedly compares two memory regions that are
// either equal or different only in their final character.
template <typename Function>
ABSL_ATTRIBUTE_ALWAYS_INLINE inline void CompareLoop(benchmark::State& state,
bool test_equal_strings,
int size, Function func) {
const int kIterMult = 4; // Iteration multiplier for better timing resolution
CHECK_GT(size, 0);
char* data = static_cast<char*>(malloc(size * 2));
memset(data, 'a', size * 2);
char* a = data;
char* b = data + size;
char last = a[size - 1];
int num = 0;
for (auto _ : state) {
for (int i = 0; i < kIterMult; ++i) {
b[size - 1] = test_equal_strings ? last : last ^ 1;
num += func(a, b, size);
}
}
state.SetBytesProcessed(static_cast<int64_t>(state.iterations()) * size);
benchmark::DoNotOptimize(num);
free(data);
}
void BM_memcmp(benchmark::State& state) {
CompareLoop(state, false, state.range(0), memcmp);
}
BENCHMARK(BM_memcmp)->DenseRange(1, 9)->Range(32, 8 << 20);
void BM_fastmemcmp_inlined(benchmark::State& state) {
CompareLoop(state, false, state.range(0),
absl::strings_internal::fastmemcmp_inlined);
}
BENCHMARK(BM_fastmemcmp_inlined)->DenseRange(1, 9)->Range(32, 8 << 20);
void BM_memeq(benchmark::State& state) {
CompareLoop(state, false, state.range(0), absl::strings_internal::memeq);
}
BENCHMARK(BM_memeq)->DenseRange(1, 9)->Range(32, 8 << 20);
void BM_memeq_equal(benchmark::State& state) {
CompareLoop(state, true, state.range(0), absl::strings_internal::memeq);
}
BENCHMARK(BM_memeq_equal)->DenseRange(1, 9)->Range(32, 8 << 20);
bool StringLess(const std::string& x, const std::string& y) { return x < y; }
bool StringEqual(const std::string& x, const std::string& y) { return x == y; }
bool StdEqual(const std::string& x, const std::string& y) {
return x.size() == y.size() &&
std::equal(x.data(), x.data() + x.size(), y.data());
}
// Benchmark for x < y, where x and y are strings that differ in only their
// final char. That should be more-or-less the worst case for <.
void BM_string_less(benchmark::State& state) {
StringCompareLoop(state, false, state.range(0) - 1, state.range(0),
StringLess);
}
BENCHMARK(BM_string_less)->DenseRange(1, 9)->Range(32, 1 << 20);
// Benchmark for x < y, where x and y are strings that differ in only their
// first char. That should be more-or-less the best case for <.
void BM_string_less_easy(benchmark::State& state) {
StringCompareLoop(state, false, 0, state.range(0), StringLess);
}
BENCHMARK(BM_string_less_easy)->DenseRange(1, 9)->Range(32, 1 << 20);
void BM_string_equal(benchmark::State& state) {
StringCompareLoop(state, false, state.range(0) - 1, state.range(0),
StringEqual);
}
BENCHMARK(BM_string_equal)->DenseRange(1, 9)->Range(32, 1 << 20);
void BM_string_equal_equal(benchmark::State& state) {
StringCompareLoop(state, true, std::string::npos, state.range(0), StringEqual);
}
BENCHMARK(BM_string_equal_equal)->DenseRange(1, 9)->Range(32, 1 << 20);
void BM_std_equal(benchmark::State& state) {
StringCompareLoop(state, false, state.range(0) - 1, state.range(0), StdEqual);
}
BENCHMARK(BM_std_equal)->DenseRange(1, 9)->Range(32, 1 << 20);
void BM_std_equal_equal(benchmark::State& state) {
StringCompareLoop(state, true, std::string::npos, state.range(0), StdEqual);
}
BENCHMARK(BM_std_equal_equal)->DenseRange(1, 9)->Range(32, 1 << 20);
void BM_string_equal_unequal_lengths(benchmark::State& state) {
const int size = state.range(0);
std::string a(size, 'a');
std::string b(size + 1, 'a');
int count = 0;
for (auto _ : state) {
b[size - 1] = 'a';
count += (a == b);
}
benchmark::DoNotOptimize(count);
}
BENCHMARK(BM_string_equal_unequal_lengths)->Arg(1)->Arg(1 << 20);
void BM_stdstring_equal_unequal_lengths(benchmark::State& state) {
const int size = state.range(0);
std::string a(size, 'a');
std::string b(size + 1, 'a');
int count = 0;
for (auto _ : state) {
b[size - 1] = 'a';
count += (a == b);
}
benchmark::DoNotOptimize(count);
}
BENCHMARK(BM_stdstring_equal_unequal_lengths)->Arg(1)->Arg(1 << 20);
} // namespace