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

[Nikolas Klauser via libcxx-commits]

================
@@ -0,0 +1,134 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 ranges_find_last_if = [](auto first, auto last, auto const& value) {
+    return std::ranges::find_last_if(first, last, [&](auto element) {
+      benchmark::DoNotOptimize(element);
+      return element == value;
+    });
+  };
+  auto ranges_find_last_if_not = [](auto first, auto last, auto const& value) {
+    return std::ranges::find_last_if_not(first, last, [&](auto element) {
+      benchmark::DoNotOptimize(element);
+      return element != value;
+    });
+  };
+
+  // Benchmark ranges::{find_last,find_last_if,find_last_if_not} where the last element
+  // is found 25% into the sequence
+  {
+    auto bm = []<class Container>(std::string name, auto find_last) {
+      benchmark::RegisterBenchmark(
+          name,
+          [find_last](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);
+
+            // put the element we're searching for at 25% of the sequence
+            *std::next(c.begin(), size / 4) = y;
+
+            for ([[maybe_unused]] auto _ : st) {
+              benchmark::DoNotOptimize(c);
+              benchmark::DoNotOptimize(y);
+              auto result = find_last(c.begin(), c.end(), y);
+              benchmark::DoNotOptimize(result);
+            }
+          })
+          ->Arg(8)
+          ->Arg(1024)
+          ->Arg(8192)
+          ->Arg(1 << 20);
+    };
+
+    // find_last
+    bm.operator()<std::vector<char>>("rng::find_last(vector<char>) (bail 25%)", std::ranges::find_last);
+    bm.operator()<std::vector<int>>("rng::find_last(vector<int>) (bail 25%)", std::ranges::find_last);
+    bm.operator()<std::deque<int>>("rng::find_last(deque<int>) (bail 25%)", std::ranges::find_last);
+    bm.operator()<std::list<int>>("rng::find_last(list<int>) (bail 25%)", std::ranges::find_last);
----------------
philnik777 wrote:

Also here: we should check with `forward_list`.

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