9827440f1e
Previously, the segmented iterator optimization was limited to `std::{for_each, for_each_n}`. This patch
extends the optimization to `std::ranges::for_each` and `std::ranges::for_each_n`, ensuring consistent
optimizations across these algorithms. This patch first generalizes the `std` algorithms by introducing
a `Projection` parameter, which is set to `__identity` for the `std` algorithms. Then we let the `ranges`
algorithms to directly call their `std` counterparts with a general `__proj` argument. Benchmarks
demonstrate performance improvements of up to 21.4x for ``std::deque::iterator`` and 22.3x for
``join_view`` of ``vector<vector<char>>``.
Addresses a subtask of #102817.
96 lines
3.5 KiB
C++
96 lines
3.5 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: c++03, c++11, c++14, c++17
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#include <algorithm>
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#include <cstddef>
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#include <deque>
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#include <list>
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#include <ranges>
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#include <string>
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#include <vector>
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#include <benchmark/benchmark.h>
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int main(int argc, char** argv) {
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auto std_for_each = [](auto first, auto last, auto f) { return std::for_each(first, last, f); };
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// {std,ranges}::for_each
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{
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auto bm = []<class Container>(std::string name, auto for_each) {
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using ElemType = typename Container::value_type;
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benchmark::RegisterBenchmark(
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name,
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[for_each](auto& st) {
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std::size_t const size = st.range(0);
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Container c(size, 1);
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auto first = c.begin();
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auto last = c.end();
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for ([[maybe_unused]] auto _ : st) {
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benchmark::DoNotOptimize(c);
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auto result = for_each(first, last, [](ElemType& x) { x = std::clamp<ElemType>(x, 10, 100); });
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benchmark::DoNotOptimize(result);
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}
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})
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->Arg(8)
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->Arg(32)
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->Arg(50) // non power-of-two
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->Arg(8192);
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};
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bm.operator()<std::vector<int>>("std::for_each(vector<int>)", std_for_each);
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bm.operator()<std::deque<int>>("std::for_each(deque<int>)", std_for_each);
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bm.operator()<std::list<int>>("std::for_each(list<int>)", std_for_each);
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bm.operator()<std::vector<int>>("rng::for_each(vector<int>)", std::ranges::for_each);
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bm.operator()<std::deque<int>>("rng::for_each(deque<int>)", std::ranges::for_each);
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bm.operator()<std::list<int>>("rng::for_each(list<int>)", std::ranges::for_each);
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}
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// {std,ranges}::for_each for join_view
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{
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auto bm = []<class Container>(std::string name, auto for_each) {
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using C1 = typename Container::value_type;
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using ElemType = typename C1::value_type;
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benchmark::RegisterBenchmark(
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name,
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[for_each](auto& st) {
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std::size_t const size = st.range(0);
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std::size_t const seg_size = 256;
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std::size_t const segments = (size + seg_size - 1) / seg_size;
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Container c(segments);
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for (std::size_t i = 0, n = size; i < segments; ++i, n -= seg_size) {
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c[i].resize(std::min(seg_size, n), ElemType(1));
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}
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auto view = c | std::views::join;
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auto first = view.begin();
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auto last = view.end();
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for ([[maybe_unused]] auto _ : st) {
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benchmark::DoNotOptimize(c);
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auto result = for_each(first, last, [](ElemType& x) { x = std::clamp<ElemType>(x, 10, 100); });
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benchmark::DoNotOptimize(result);
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}
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})
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->Arg(8)
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->Arg(32)
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->Arg(50) // non power-of-two
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->Arg(8192);
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};
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bm.operator()<std::vector<std::vector<int>>>("std::for_each(join_view(vector<vector<int>>))", std_for_each);
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bm.operator()<std::vector<std::vector<int>>>("rng::for_each(join_view(vector<vector<int>>)", std::ranges::for_each);
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}
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benchmark::Initialize(&argc, argv);
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benchmark::RunSpecifiedBenchmarks();
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benchmark::Shutdown();
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return 0;
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}
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