Add 'third_party/abseil_cpp/' from commit '768eb2ca28'

git-subtree-dir: third_party/abseil_cpp
git-subtree-mainline: ffb2ae54be
git-subtree-split: 768eb2ca28

third_party/abseil_cpp/absl/synchronization/internal/graphcycles_benchmark.cc

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+// Copyright 2018 The Abseil Authors.
+//
+// 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
+//
+//      https://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 "absl/synchronization/internal/graphcycles.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+#include "absl/base/internal/raw_logging.h"
+
+namespace {
+
+void BM_StressTest(benchmark::State& state) {
+  const int num_nodes = state.range(0);
+  while (state.KeepRunningBatch(num_nodes)) {
+    absl::synchronization_internal::GraphCycles g;
+    std::vector<absl::synchronization_internal::GraphId> nodes(num_nodes);
+    for (int i = 0; i < num_nodes; i++) {
+      nodes[i] = g.GetId(reinterpret_cast<void*>(static_cast<uintptr_t>(i)));
+    }
+    for (int i = 0; i < num_nodes; i++) {
+      int end = std::min(num_nodes, i + 5);
+      for (int j = i + 1; j < end; j++) {
+        ABSL_RAW_CHECK(g.InsertEdge(nodes[i], nodes[j]), "");
+      }
+    }
+  }
+}
+BENCHMARK(BM_StressTest)->Range(2048, 1048576);
+
+}  // namespace