[libc++] Add benchmarks for is_permutation and its std::ranges counte…

libcxx/test/benchmarks/algorithms/is_permutation.bench.cpp

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+//===----------------------------------------------------------------------===//
+//
+// 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 <random>
+#include <vector>
+#include <numeric>
+#include <benchmark/benchmark.h>
+
+void BenchmarkSizes(benchmark::internal::Benchmark* Benchmark) {
+  Benchmark->DenseRange(1, 8);
+  for (size_t i = 16; i != 1 << 20; i *= 2) {
+    Benchmark->Arg(i - 1);
+    Benchmark->Arg(i);
+    Benchmark->Arg(i + 1);
+  }
+}
+
+// Test std::is_permutation when sequences are identical
+static void bm_std_is_permutation_same(benchmark::State& state) {
+  std::vector<int> vec1(state.range(), 1);
+  std::vector<int> vec2(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(vec1);
+    benchmark::DoNotOptimize(vec2);
+    benchmark::DoNotOptimize(std::is_permutation(vec1.begin(), vec1.end(), vec2.begin()));
+  }
+}
+BENCHMARK(bm_std_is_permutation_same)->Apply(BenchmarkSizes);
+
+// Test std::ranges::is_permutation when sequences are identical
+static void bm_ranges_is_permutation_same(benchmark::State& state) {
+  std::vector<int> vec1(state.range(), 1);
+  std::vector<int> vec2(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(vec1);
+    benchmark::DoNotOptimize(vec2);
+    benchmark::DoNotOptimize(std::ranges::is_permutation(vec1, vec2));
+  }
+}
+BENCHMARK(bm_ranges_is_permutation_same)->Apply(BenchmarkSizes);
+
+// Test std::is_permutation when sequences are permutations
+static void bm_std_is_permutation_shuffled(benchmark::State& state) {
+  std::vector<int> vec1(state.range());
+  std::iota(vec1.begin(), vec1.end(), 0);
+  auto vec2 = vec1;
+  std::mt19937 gen(42);
+  std::shuffle(vec2.begin(), vec2.end(), gen);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(vec1);
+    benchmark::DoNotOptimize(vec2);
+    benchmark::DoNotOptimize(std::is_permutation(vec1.begin(), vec1.end(), vec2.begin()));
+  }
+}
+BENCHMARK(bm_std_is_permutation_shuffled)->Apply(BenchmarkSizes);
+
+// Test std::ranges::is_permutation when sequences are permutations
+static void bm_ranges_is_permutation_shuffled(benchmark::State& state) {
+  std::vector<int> vec1(state.range());
+  std::iota(vec1.begin(), vec1.end(), 0);
+  auto vec2 = vec1;
+  std::mt19937 gen(42);
+  std::shuffle(vec2.begin(), vec2.end(), gen);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(vec1);
+    benchmark::DoNotOptimize(vec2);
+    benchmark::DoNotOptimize(std::ranges::is_permutation(vec1, vec2));
+  }
+}
+BENCHMARK(bm_ranges_is_permutation_shuffled)->Apply(BenchmarkSizes);
+
+// Test std::is_permutation when sequences differ in last element
+static void bm_std_is_permutation_diff_last(benchmark::State& state) {
+  std::vector<int> vec1(state.range(), 1);
+  std::vector<int> vec2(state.range(), 1);
+  vec2.back() = 2;
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(vec1);
+    benchmark::DoNotOptimize(vec2);
+    benchmark::DoNotOptimize(std::is_permutation(vec1.begin(), vec1.end(), vec2.begin()));
+  }
+}
+BENCHMARK(bm_std_is_permutation_diff_last)->Apply(BenchmarkSizes);
+
+// Test std::ranges::is_permutation when sequences differ in last element
+static void bm_ranges_is_permutation_diff_last(benchmark::State& state) {
+  std::vector<int> vec1(state.range(), 1);
+  std::vector<int> vec2(state.range(), 1);
+  vec2.back() = 2;
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(vec1);
+    benchmark::DoNotOptimize(vec2);
+    benchmark::DoNotOptimize(std::ranges::is_permutation(vec1, vec2));
+  }
+}
+BENCHMARK(bm_ranges_is_permutation_diff_last)->Apply(BenchmarkSizes);
+
+BENCHMARK_MAIN();