Abseil Common Libraries (C++) (grcp 依赖)
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323 lines
12 KiB
323 lines
12 KiB
// 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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