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

[Nikolas Klauser via libcxx-commits]

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@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_ends_with_pred = [](auto first1, auto last1, auto first2, auto last2) {
+    return std::ranges::ends_with(first1, last1, first2, last2, [](auto x, auto y) {
+      benchmark::DoNotOptimize(x);
+      benchmark::DoNotOptimize(y);
+      return x == y;
+    });
+  };
+
+  // Benchmark ranges::ends_with where we find the mismatching element at the very end.
+  {
+    auto bm = []<class Container>(std::string name, auto ends_with) {
+      benchmark::RegisterBenchmark(
+          name,
+          [ends_with](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 c1(size, x);
+            Container c2(size, x);
+            c2.back() = y;
+
+            for ([[maybe_unused]] auto _ : st) {
+              benchmark::DoNotOptimize(c1);
+              benchmark::DoNotOptimize(c2);
+              auto result = ends_with(c1.begin(), c1.end(), c2.begin(), c2.end());
+              benchmark::DoNotOptimize(result);
+            }
+          })
+          ->Arg(8)
+          ->Arg(1024)
+          ->Arg(8192)
+          ->Arg(1 << 20);
+    };
+    bm.operator()<std::vector<int>>("rng::ends_with(vector<int>) (mismatch at end)", std::ranges::ends_with);
+    bm.operator()<std::deque<int>>("rng::ends_with(deque<int>) (mismatch at end)", std::ranges::ends_with);
+    bm.operator()<std::list<int>>("rng::ends_with(list<int>) (mismatch at end)", std::ranges::ends_with);
+
+    bm.operator()<std::vector<int>>("rng::ends_with(vector<int>, pred) (mismatch at end)", ranges_ends_with_pred);
+    bm.operator()<std::deque<int>>("rng::ends_with(deque<int>, pred) (mismatch at end)", ranges_ends_with_pred);
+    bm.operator()<std::list<int>>("rng::ends_with(list<int>, pred) (mismatch at end)", ranges_ends_with_pred);
+  }
+
+  // Benchmark ranges::ends_with where we find the mismatching element at the very beginning.
+  {
+    auto bm = []<class Container>(std::string name, auto ends_with) {
+      benchmark::RegisterBenchmark(
+          name,
+          [ends_with](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 c1(size, x);
+            Container c2(size, x);
+            c2.front() = y;
+
+            for ([[maybe_unused]] auto _ : st) {
+              benchmark::DoNotOptimize(c1);
+              benchmark::DoNotOptimize(c2);
+              auto result = ends_with(c1.begin(), c1.end(), c2.begin(), c2.end());
+              benchmark::DoNotOptimize(result);
+            }
+          })
+          ->Arg(8)
+          ->Arg(1024)
+          ->Arg(8192)
+          ->Arg(1 << 20);
+    };
+    bm.operator()<std::vector<int>>("rng::ends_with(vector<int>) (mismatch at start)", std::ranges::ends_with);
+    bm.operator()<std::deque<int>>("rng::ends_with(deque<int>) (mismatch at start)", std::ranges::ends_with);
+    bm.operator()<std::list<int>>("rng::ends_with(list<int>) (mismatch at start)", std::ranges::ends_with);
----------------
philnik777 wrote:

I think we should also test with a `std::forward_list` here, since we're caring about the end of the range, which is quite unusual.

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