bkietz commented on a change in pull request #8716: URL: https://github.com/apache/arrow/pull/8716#discussion_r578613771
########## File path: cpp/src/arrow/util/cache_benchmark.cc ########## @@ -0,0 +1,146 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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 "benchmark/benchmark.h" + +#include <cstdint> +#include <string> +#include <vector> + +#include "arrow/array.h" +#include "arrow/testing/random.h" +#include "arrow/util/cache_internal.h" +#include "arrow/util/checked_cast.h" +#include "arrow/util/logging.h" +#include "arrow/util/macros.h" + +namespace arrow { +namespace internal { + +static constexpr int32_t kCacheSize = 100; +static constexpr int32_t kSmallKeyLength = 8; +static constexpr int32_t kLargeKeyLength = 64; +static constexpr int32_t kSmallValueLength = 16; +static constexpr int32_t kLargeValueLength = 1024; + +static std::vector<std::string> MakeStrings(int64_t nvalues, int64_t min_length, + int64_t max_length) { + auto rng = ::arrow::random::RandomArrayGenerator(42); + auto arr = checked_pointer_cast<StringArray>(rng.String( + nvalues, static_cast<int32_t>(min_length), static_cast<int32_t>(max_length))); + std::vector<std::string> vec(nvalues); + for (int64_t i = 0; i < nvalues; ++i) { + vec[i] = arr->GetString(i); + } + return vec; +} + +static std::vector<std::string> MakeStrings(int64_t nvalues, int64_t length) { + return MakeStrings(nvalues, length, length); +} + +template <typename Cache, typename Key, typename Value> +static void BenchmarkCacheLookups(benchmark::State& state, const std::vector<Key>& keys, + const std::vector<Value>& values) { + const int32_t nitems = static_cast<int32_t>(keys.size()); + Cache cache(nitems); + for (int32_t i = 0; i < nitems; ++i) { + cache.Replace(keys[i], values[i]); + } + + for (auto _ : state) { + int64_t nfinds = 0; + for (const auto& key : keys) { + nfinds += (cache.Find(key) != nullptr); + } + benchmark::DoNotOptimize(nfinds); + ARROW_CHECK_EQ(nfinds, nitems); + } + state.SetItemsProcessed(state.iterations() * nitems); +} + +static void LRUCacheLookup(benchmark::State& state) { + const auto keys = MakeStrings(kCacheSize, state.range(0)); + const auto values = MakeStrings(kCacheSize, state.range(1)); + BenchmarkCacheLookups<LRUCache<std::string, std::string>>(state, keys, values); +} + +static void SetCacheArgs(benchmark::internal::Benchmark* bench) { + bench->Args({kSmallKeyLength, kSmallValueLength}); + bench->Args({kSmallKeyLength, kLargeValueLength}); + bench->Args({kLargeKeyLength, kSmallValueLength}); + bench->Args({kLargeKeyLength, kLargeValueLength}); +} + +BENCHMARK(LRUCacheLookup)->Apply(SetCacheArgs); + +struct Callable { + explicit Callable(std::vector<std::string> values) + : index_(0), values_(std::move(values)) {} + + std::string operator()(const std::string& key) { + // Return a value unrelated to the key + if (++index_ >= static_cast<int64_t>(values_.size())) { + index_ = 0; + } + return values_[index_]; + } + + private: + int64_t index_; + std::vector<std::string> values_; +}; + +template <typename Memoized> +static void BenchmarkMemoize(benchmark::State& state, Memoized&& mem, + const std::vector<std::string>& keys) { + // Prime memoization cache + for (const auto& key : keys) { + mem(key); + } + + for (auto _ : state) { + int64_t nbytes = 0; + for (const auto& key : keys) { + nbytes += static_cast<int64_t>(mem(key).length()); + } + benchmark::DoNotOptimize(nbytes); + } + state.SetItemsProcessed(state.iterations() * keys.size()); +} + +static void MemoizeLRUCached(benchmark::State& state) { + const auto keys = MakeStrings(kCacheSize, state.range(0)); + const auto values = MakeStrings(kCacheSize, state.range(1)); Review comment: If the string set is exactly as large as the cache then the only overhead you're measuring is promotion inside a static set. By contrast if the string set is larger than the cast you will measure the cost of replacement as well. The latter seems useful to know when deciding how large to make a cache, since it represents the penalty for guessing too low. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
