[libcxx-commits] [libcxx] [libc++] Refactor and add benchmarks from [alg.nonmodifying] (PR #128206)

[Nikolas Klauser via libcxx-commits]

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@@ -0,0 +1,102 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+#include <algorithm>
+#include <cstddef>
+#include <deque>
+#include <list>
+#include <string>
+#include <vector>
+
+#include <benchmark/benchmark.h>
+#include "../../GenerateInput.h"
+
+int main(int argc, char** argv) {
+  auto std_find_end = [](auto first1, auto last1, auto first2, auto last2) {
+    return std::find_end(first1, last1, first2, last2);
+  };
+
+  // Benchmark {std,ranges}::find_end where the subsequence is found
+  // 25% into the sequence
+  {
+    auto bm = []<class Container>(std::string name, auto find_end) {
+      benchmark::RegisterBenchmark(
+          name,
+          [find_end](auto& st) {
+            std::size_t const size = st.range(0);
+            using ValueType        = typename Container::value_type;
+            ValueType x            = Generate<ValueType>::random();
+            ValueType y            = random_different_from({x});
+            Container c(size, x);
+            Container subrange(size / 10, y); // subrange of length 10% of the full range
+
+            // put the element we're searching for at 25% of the sequence
+            std::ranges::copy(subrange, std::next(c.begin(), c.size() / 4));
+
+            for ([[maybe_unused]] auto _ : st) {
+              benchmark::DoNotOptimize(c);
+              benchmark::DoNotOptimize(subrange);
+              auto result = find_end(c.begin(), c.end(), subrange.begin(), subrange.end());
+              benchmark::DoNotOptimize(result);
+            }
+          })
+          ->Arg(1024)
+          ->Arg(8192)
+          ->Arg(1 << 20);
+    };
+    bm.operator()<std::vector<int>>("std::find_end(vector<int>) (bail 25%)", std_find_end);
+    bm.operator()<std::deque<int>>("std::find_end(deque<int>) (bail 25%)", std_find_end);
+    bm.operator()<std::list<int>>("std::find_end(list<int>) (bail 25%)", std_find_end);
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philnik777 wrote:

Here we should probably also benchmark with a `forward_list`.

https://github.com/llvm/llvm-project/pull/128206