Adding Google benchmarking library.

third_party/google_benchmark/test/map_test.cc

Index: third_party/google_benchmark/test/map_test.cc
diff --git a/third_party/google_benchmark/test/map_test.cc b/third_party/google_benchmark/test/map_test.cc
new file mode 100644
index 0000000000000000000000000000000000000000..83457c9981cde477e74f7a61b06061490f325cdc
--- /dev/null
+++ b/third_party/google_benchmark/test/map_test.cc
@@ -0,0 +1,56 @@
+#include "benchmark/benchmark.h"
+
+#include <cstdlib>
+#include <map>
+
+namespace {
+
+std::map<int, int> ConstructRandomMap(int size) {
+  std::map<int, int> m;
+  for (int i = 0; i < size; ++i) {
+    m.insert(std::make_pair(rand() % size, rand() % size));
+  }
+  return m;
+}
+
+}  // namespace
+
+// Basic version.
+static void BM_MapLookup(benchmark::State& state) {
+  const int size = state.range(0);
+  while (state.KeepRunning()) {
+    state.PauseTiming();
+    std::map<int, int> m = ConstructRandomMap(size);
+    state.ResumeTiming();
+    for (int i = 0; i < size; ++i) {
+      benchmark::DoNotOptimize(m.find(rand() % size));
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * size);
+}
+BENCHMARK(BM_MapLookup)->Range(1 << 3, 1 << 12);
+
+// Using fixtures.
+class MapFixture : public ::benchmark::Fixture {
+ public:
+  void SetUp(const ::benchmark::State& st) {
+    m = ConstructRandomMap(st.range(0));
+  }
+
+  void TearDown(const ::benchmark::State&) { m.clear(); }
+
+  std::map<int, int> m;
+};
+
+BENCHMARK_DEFINE_F(MapFixture, Lookup)(benchmark::State& state) {
+  const int size = state.range(0);
+  while (state.KeepRunning()) {
+    for (int i = 0; i < size; ++i) {
+      benchmark::DoNotOptimize(m.find(rand() % size));
+    }
+  }
+  state.SetItemsProcessed(state.iterations() * size);
+}
+BENCHMARK_REGISTER_F(MapFixture, Lookup)->Range(1 << 3, 1 << 12);
+
+BENCHMARK_MAIN()