126 lines
4.7 KiB
C++
126 lines
4.7 KiB
C++
// Copyright 2017 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 <cstdint>
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#include <cstring>
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#include "benchmark/benchmark.h"
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#include "absl/algorithm/algorithm.h"
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namespace {
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// The range of sequence sizes to benchmark.
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constexpr int kMinBenchmarkSize = 1024;
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constexpr int kMaxBenchmarkSize = 8 * 1024 * 1024;
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// A user-defined type for use in equality benchmarks. Note that we expect
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// std::memcmp to win for this type: libstdc++'s std::equal only defers to
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// memcmp for integral types. This is because it is not straightforward to
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// guarantee that std::memcmp would produce a result "as-if" compared by
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// operator== for other types (example gotchas: NaN floats, structs with
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// padding).
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struct EightBits {
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explicit EightBits(int /* unused */) : data(0) {}
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bool operator==(const EightBits& rhs) const { return data == rhs.data; }
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uint8_t data;
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};
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template <typename T>
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void BM_absl_equal_benchmark(benchmark::State& state) {
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std::vector<T> xs(state.range(0), T(0));
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std::vector<T> ys = xs;
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while (state.KeepRunning()) {
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const bool same = absl::equal(xs.begin(), xs.end(), ys.begin(), ys.end());
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benchmark::DoNotOptimize(same);
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}
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}
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template <typename T>
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void BM_std_equal_benchmark(benchmark::State& state) {
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std::vector<T> xs(state.range(0), T(0));
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std::vector<T> ys = xs;
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while (state.KeepRunning()) {
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const bool same = std::equal(xs.begin(), xs.end(), ys.begin());
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benchmark::DoNotOptimize(same);
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}
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}
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template <typename T>
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void BM_memcmp_benchmark(benchmark::State& state) {
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std::vector<T> xs(state.range(0), T(0));
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std::vector<T> ys = xs;
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while (state.KeepRunning()) {
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const bool same =
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std::memcmp(xs.data(), ys.data(), xs.size() * sizeof(T)) == 0;
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benchmark::DoNotOptimize(same);
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}
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}
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// The expectation is that the compiler should be able to elide the equality
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// comparison altogether for sufficiently simple types.
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template <typename T>
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void BM_absl_equal_self_benchmark(benchmark::State& state) {
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std::vector<T> xs(state.range(0), T(0));
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while (state.KeepRunning()) {
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const bool same = absl::equal(xs.begin(), xs.end(), xs.begin(), xs.end());
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benchmark::DoNotOptimize(same);
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}
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}
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BENCHMARK_TEMPLATE(BM_absl_equal_benchmark, uint8_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_std_equal_benchmark, uint8_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_memcmp_benchmark, uint8_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_self_benchmark, uint8_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_benchmark, uint16_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_std_equal_benchmark, uint16_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_memcmp_benchmark, uint16_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_self_benchmark, uint16_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_benchmark, uint32_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_std_equal_benchmark, uint32_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_memcmp_benchmark, uint32_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_self_benchmark, uint32_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_benchmark, uint64_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_std_equal_benchmark, uint64_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_memcmp_benchmark, uint64_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_self_benchmark, uint64_t)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_benchmark, EightBits)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_std_equal_benchmark, EightBits)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_memcmp_benchmark, EightBits)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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BENCHMARK_TEMPLATE(BM_absl_equal_self_benchmark, EightBits)
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->Range(kMinBenchmarkSize, kMaxBenchmarkSize);
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} // namespace
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