Add benchmarks for mjSORT macro.

PiperOrigin-RevId: 781555531
Change-Id: Ia33b5512fbf65b08931037859d8c6062b018d760

Author: yuvaltassa

test/benchmark/sort_benchmark_test.cc

@@ -0,0 +1,155 @@
+// Copyright 2025 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <algorithm>
+#include <random>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include <absl/base/attributes.h>
+#include <mujoco/mujoco.h>
+#include "src/engine/engine_sort.h"
+
+namespace mujoco {
+namespace {
+
+// A struct with data to be sorted.
+struct Sortable {
+  mjtNum value;
+  int id1;
+  int id2;
+};
+
+// Comparison function for Sortable struct.
+int CompareSortable(const Sortable* a, const Sortable* b, void* context) {
+  if (a->value < b->value) {
+    return -1;
+  } else if (a->value == b->value) {
+    return 0;
+  } else {
+    return 1;
+  }
+}
+
+// Instantiate the sort function.
+mjSORT(SortSortable, Sortable, CompareSortable)
+
+// Generate data for sorting benchmarks.
+std::vector<Sortable> GenerateData(int n, double unsorted_fraction) {
+  std::vector<Sortable> data(n);
+  for (int i = 0; i < n; ++i) {
+    data[i] = {static_cast<mjtNum>(i), i, -i};
+  }
+
+  if (unsorted_fraction > 0.0) {
+    std::mt19937 g(12345);
+    if (unsorted_fraction >= 1.0) {
+      std::shuffle(data.begin(), data.end(), g);
+    } else {
+      int num_to_shuffle = n * unsorted_fraction;
+      for (int i = 0; i < num_to_shuffle; ++i) {
+        int j = std::uniform_int_distribution<int>(i, n - 1)(g);
+        std::swap(data[i], data[j]);
+      }
+    }
+  }
+  return data;
+}
+
+// Run a sorting benchmark with the given size and unsorted fraction.
+ABSL_ATTRIBUTE_NO_TAIL_CALL static void SortBenchmark(
+    benchmark::State& state, int n, double unsorted_fraction) {
+  auto data = GenerateData(n, unsorted_fraction);
+  std::vector<Sortable> buf(n);
+  std::vector<Sortable> copy = data;
+
+  for (auto s : state) {
+    state.PauseTiming();
+    copy = data;
+    state.ResumeTiming();
+    SortSortable(copy.data(), buf.data(), n, nullptr);
+  }
+
+  state.counters["items/s"] =
+      benchmark::Counter(state.iterations() * n, benchmark::Counter::kIsRate);
+}
+
+// Define benchmarks.
+void BM_Sort_1k_AlmostSorted(benchmark::State& state) {
+  SortBenchmark(state, 1000, 0.05);
+}
+BENCHMARK(BM_Sort_1k_AlmostSorted);
+
+void BM_Sort_1k_Random(benchmark::State& state) {
+  SortBenchmark(state, 1000, 1.0);
+}
+BENCHMARK(BM_Sort_1k_Random);
+
+void BM_Sort_100k_AlmostSorted(benchmark::State& state) {
+  SortBenchmark(state, 100000, 0.05);
+}
+BENCHMARK(BM_Sort_100k_AlmostSorted);
+
+void BM_Sort_100k_Random(benchmark::State& state) {
+  SortBenchmark(state, 100000, 1.0);
+}
+BENCHMARK(BM_Sort_100k_Random);
+
+// Run a sorting benchmark with std::stable_sort
+ABSL_ATTRIBUTE_NO_TAIL_CALL static void StdSortBenchmark(
+    benchmark::State& state, int n, double unsorted_fraction) {
+  auto data = GenerateData(n, unsorted_fraction);
+  std::vector<Sortable> copy = data;
+
+  for (auto s : state) {
+    state.PauseTiming();
+    copy = data;
+    state.ResumeTiming();
+    std::stable_sort(
+        copy.begin(), copy.end(),
+        [](const Sortable& a, const Sortable& b) { return a.value < b.value; });
+  }
+
+  state.counters["items/s"] =
+      benchmark::Counter(state.iterations() * n, benchmark::Counter::kIsRate);
+}
+
+void BM_StdSort_1k_AlmostSorted(benchmark::State& state) {
+  StdSortBenchmark(state, 1000, 0.05);
+}
+BENCHMARK(BM_StdSort_1k_AlmostSorted);
+
+void BM_StdSort_1k_Random(benchmark::State& state) {
+  StdSortBenchmark(state, 1000, 1.0);
+}
+BENCHMARK(BM_StdSort_1k_Random);
+
+void BM_StdSort_100k_AlmostSorted(benchmark::State& state) {
+  StdSortBenchmark(state, 100000, 0.05);
+}
+BENCHMARK(BM_StdSort_100k_AlmostSorted);
+
+void BM_StdSort_100k_Random(benchmark::State& state) {
+  StdSortBenchmark(state, 100000, 1.0);
+}
+BENCHMARK(BM_StdSort_100k_Random);
+
+}  // namespace
+}  // namespace mujoco
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  benchmark::RunSpecifiedBenchmarks();
+  return 0;
+}