fc8dc48020
git-subtree-dir: third_party/abseil_cpp git-subtree-mainline:ffb2ae54begit-subtree-split:768eb2ca28
323 lines
12 KiB
C++
323 lines
12 KiB
C++
// Copyright 2018 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "absl/strings/internal/memutil.h"
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#include <algorithm>
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#include <cstdlib>
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#include "benchmark/benchmark.h"
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#include "absl/strings/ascii.h"
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// We fill the haystack with aaaaaaaaaaaaaaaaaa...aaaab.
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// That gives us:
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// - an easy search: 'b'
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// - a medium search: 'ab'. That means every letter is a possible match.
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// - a pathological search: 'aaaaaa.......aaaaab' (half as many a's as haytack)
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// We benchmark case-sensitive and case-insensitive versions of
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// three memmem implementations:
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// - memmem() from memutil.h
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// - search() from STL
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// - memmatch(), a custom implementation using memchr and memcmp.
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// Here are sample results:
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//
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// Run on (12 X 3800 MHz CPU s)
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// CPU Caches:
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// L1 Data 32K (x6)
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// L1 Instruction 32K (x6)
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// L2 Unified 256K (x6)
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// L3 Unified 15360K (x1)
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// ----------------------------------------------------------------
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// Benchmark Time CPU Iterations
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// ----------------------------------------------------------------
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// BM_Memmem 3583 ns 3582 ns 196469 2.59966GB/s
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// BM_MemmemMedium 13743 ns 13742 ns 50901 693.986MB/s
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// BM_MemmemPathological 13695030 ns 13693977 ns 51 713.133kB/s
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// BM_Memcasemem 3299 ns 3299 ns 212942 2.82309GB/s
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// BM_MemcasememMedium 16407 ns 16406 ns 42170 581.309MB/s
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// BM_MemcasememPathological 17267745 ns 17266030 ns 41 565.598kB/s
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// BM_Search 1610 ns 1609 ns 431321 5.78672GB/s
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// BM_SearchMedium 11111 ns 11110 ns 63001 858.414MB/s
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// BM_SearchPathological 12117390 ns 12116397 ns 58 805.984kB/s
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// BM_Searchcase 3081 ns 3081 ns 229949 3.02313GB/s
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// BM_SearchcaseMedium 16003 ns 16001 ns 44170 595.998MB/s
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// BM_SearchcasePathological 15823413 ns 15821909 ns 44 617.222kB/s
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// BM_Memmatch 197 ns 197 ns 3584225 47.2951GB/s
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// BM_MemmatchMedium 52333 ns 52329 ns 13280 182.244MB/s
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// BM_MemmatchPathological 659799 ns 659727 ns 1058 14.4556MB/s
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// BM_Memcasematch 5460 ns 5460 ns 127606 1.70586GB/s
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// BM_MemcasematchMedium 32861 ns 32857 ns 21258 290.248MB/s
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// BM_MemcasematchPathological 15154243 ns 15153089 ns 46 644.464kB/s
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// BM_MemmemStartup 5 ns 5 ns 150821500
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// BM_SearchStartup 5 ns 5 ns 150644203
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// BM_MemmatchStartup 7 ns 7 ns 97068802
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//
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// Conclusions:
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//
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// The following recommendations are based on the sample results above. However,
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// we have found that the performance of STL search can vary significantly
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// depending on compiler and standard library implementation. We recommend you
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// run the benchmarks for yourself on relevant platforms.
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//
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// If you need case-insensitive, STL search is slightly better than memmem for
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// all cases.
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//
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// Case-sensitive is more subtle:
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// Custom memmatch is _very_ fast at scanning, so if you have very few possible
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// matches in your haystack, that's the way to go. Performance drops
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// significantly with more matches.
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//
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// STL search is slightly faster than memmem in the medium and pathological
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// benchmarks. However, the performance of memmem is currently more dependable
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// across platforms and build configurations.
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namespace {
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constexpr int kHaystackSize = 10000;
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constexpr int64_t kHaystackSize64 = kHaystackSize;
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const char* MakeHaystack() {
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char* haystack = new char[kHaystackSize];
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for (int i = 0; i < kHaystackSize - 1; ++i) haystack[i] = 'a';
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haystack[kHaystackSize - 1] = 'b';
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return haystack;
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}
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const char* const kHaystack = MakeHaystack();
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void BM_Memmem(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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absl::strings_internal::memmem(kHaystack, kHaystackSize, "b", 1));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_Memmem);
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void BM_MemmemMedium(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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absl::strings_internal::memmem(kHaystack, kHaystackSize, "ab", 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemmemMedium);
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void BM_MemmemPathological(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(absl::strings_internal::memmem(
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kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
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kHaystackSize - kHaystackSize / 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemmemPathological);
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void BM_Memcasemem(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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absl::strings_internal::memcasemem(kHaystack, kHaystackSize, "b", 1));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_Memcasemem);
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void BM_MemcasememMedium(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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absl::strings_internal::memcasemem(kHaystack, kHaystackSize, "ab", 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemcasememMedium);
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void BM_MemcasememPathological(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(absl::strings_internal::memcasemem(
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kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
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kHaystackSize - kHaystackSize / 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemcasememPathological);
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bool case_eq(const char a, const char b) {
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return absl::ascii_tolower(a) == absl::ascii_tolower(b);
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}
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void BM_Search(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize - 1,
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kHaystack + kHaystackSize));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_Search);
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void BM_SearchMedium(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize - 2,
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kHaystack + kHaystackSize));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_SearchMedium);
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void BM_SearchPathological(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize / 2,
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kHaystack + kHaystackSize));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_SearchPathological);
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void BM_Searchcase(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize - 1,
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kHaystack + kHaystackSize, case_eq));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_Searchcase);
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void BM_SearchcaseMedium(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize - 2,
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kHaystack + kHaystackSize, case_eq));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_SearchcaseMedium);
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void BM_SearchcasePathological(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(std::search(kHaystack, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize / 2,
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kHaystack + kHaystackSize, case_eq));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_SearchcasePathological);
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char* memcasechr(const char* s, int c, size_t slen) {
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c = absl::ascii_tolower(c);
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for (; slen; ++s, --slen) {
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if (absl::ascii_tolower(*s) == c) return const_cast<char*>(s);
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}
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return nullptr;
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}
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const char* memcasematch(const char* phaystack, size_t haylen,
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const char* pneedle, size_t neelen) {
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if (0 == neelen) {
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return phaystack; // even if haylen is 0
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}
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if (haylen < neelen) return nullptr;
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const char* match;
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const char* hayend = phaystack + haylen - neelen + 1;
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while ((match = static_cast<char*>(
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memcasechr(phaystack, pneedle[0], hayend - phaystack)))) {
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if (absl::strings_internal::memcasecmp(match, pneedle, neelen) == 0)
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return match;
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else
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phaystack = match + 1;
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}
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return nullptr;
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}
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void BM_Memmatch(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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absl::strings_internal::memmatch(kHaystack, kHaystackSize, "b", 1));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_Memmatch);
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void BM_MemmatchMedium(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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absl::strings_internal::memmatch(kHaystack, kHaystackSize, "ab", 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemmatchMedium);
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void BM_MemmatchPathological(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(absl::strings_internal::memmatch(
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kHaystack, kHaystackSize, kHaystack + kHaystackSize / 2,
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kHaystackSize - kHaystackSize / 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemmatchPathological);
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void BM_Memcasematch(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(memcasematch(kHaystack, kHaystackSize, "b", 1));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_Memcasematch);
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void BM_MemcasematchMedium(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(memcasematch(kHaystack, kHaystackSize, "ab", 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemcasematchMedium);
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void BM_MemcasematchPathological(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(memcasematch(kHaystack, kHaystackSize,
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kHaystack + kHaystackSize / 2,
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kHaystackSize - kHaystackSize / 2));
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}
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state.SetBytesProcessed(kHaystackSize64 * state.iterations());
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}
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BENCHMARK(BM_MemcasematchPathological);
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void BM_MemmemStartup(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(absl::strings_internal::memmem(
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kHaystack + kHaystackSize - 10, 10, kHaystack + kHaystackSize - 1, 1));
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}
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}
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BENCHMARK(BM_MemmemStartup);
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void BM_SearchStartup(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(
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std::search(kHaystack + kHaystackSize - 10, kHaystack + kHaystackSize,
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kHaystack + kHaystackSize - 1, kHaystack + kHaystackSize));
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}
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}
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BENCHMARK(BM_SearchStartup);
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void BM_MemmatchStartup(benchmark::State& state) {
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for (auto _ : state) {
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benchmark::DoNotOptimize(absl::strings_internal::memmatch(
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kHaystack + kHaystackSize - 10, 10, kHaystack + kHaystackSize - 1, 1));
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}
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}
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BENCHMARK(BM_MemmatchStartup);
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} // namespace
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