Adding Google benchmarking library.

third_party/google_benchmark/test/options_test.cc

+#include "benchmark/benchmark_api.h"
+#include <chrono>
+#include <thread>
+
+#if defined(NDEBUG)
+#undef NDEBUG
+#endif
+#include <cassert>
+
+void BM_basic(benchmark::State& state) {
+  while (state.KeepRunning()) {
+  }
+}
+
+void BM_basic_slow(benchmark::State& state) {
+  std::chrono::milliseconds sleep_duration(state.range(0));
+  while (state.KeepRunning()) {
+    std::this_thread::sleep_for(
+        std::chrono::duration_cast<std::chrono::nanoseconds>(sleep_duration));
+  }
+}
+
+BENCHMARK(BM_basic);
+BENCHMARK(BM_basic)->Arg(42);
+BENCHMARK(BM_basic_slow)->Arg(10)->Unit(benchmark::kNanosecond);
+BENCHMARK(BM_basic_slow)->Arg(100)->Unit(benchmark::kMicrosecond);
+BENCHMARK(BM_basic_slow)->Arg(1000)->Unit(benchmark::kMillisecond);
+BENCHMARK(BM_basic)->Range(1, 8);
+BENCHMARK(BM_basic)->RangeMultiplier(2)->Range(1, 8);
+BENCHMARK(BM_basic)->DenseRange(10, 15);
+BENCHMARK(BM_basic)->Args({42, 42});
+BENCHMARK(BM_basic)->Ranges({{64, 512}, {64, 512}});
+BENCHMARK(BM_basic)->MinTime(0.7);
+BENCHMARK(BM_basic)->UseRealTime();
+BENCHMARK(BM_basic)->ThreadRange(2, 4);
+BENCHMARK(BM_basic)->ThreadPerCpu();
+BENCHMARK(BM_basic)->Repetitions(3);
+
+void CustomArgs(benchmark::internal::Benchmark* b) {
+  for (int i = 0; i < 10; ++i) {
+    b->Arg(i);
+  }
+}
+
+BENCHMARK(BM_basic)->Apply(CustomArgs);
+
+void BM_explicit_iteration_count(benchmark::State& st) {
+  // Test that benchmarks specified with an explicit iteration count are
+  // only run once.
+  static bool invoked_before = false;
+  assert(!invoked_before);
+  invoked_before = true;
+
+  // Test that the requested iteration count is respected.
+  assert(st.max_iterations == 42);
+  size_t actual_iterations = 0;
+  while (st.KeepRunning())
+    ++actual_iterations;
+  assert(st.iterations() == st.max_iterations);
+  assert(st.iterations() == 42);
+
+}
+BENCHMARK(BM_explicit_iteration_count)->Iterations(42);
+
+BENCHMARK_MAIN()