barrier_test.cc
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1 // Copyright 2017 The Abseil Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // https://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
16 
17 #include <thread> // NOLINT(build/c++11)
18 #include <vector>
19 
20 #include "gtest/gtest.h"
22 #include "absl/time/clock.h"
23 
24 
25 TEST(Barrier, SanityTest) {
26  constexpr int kNumThreads = 10;
27  absl::Barrier* barrier = new absl::Barrier(kNumThreads);
28 
29  absl::Mutex mutex;
30  int counter = 0; // Guarded by mutex.
31 
32  auto thread_func = [&] {
33  if (barrier->Block()) {
34  // This thread is the last thread to reach the barrier so it is
35  // responsible for deleting it.
36  delete barrier;
37  }
38 
39  // Increment the counter.
40  absl::MutexLock lock(&mutex);
41  ++counter;
42  };
43 
44  // Start (kNumThreads - 1) threads running thread_func.
45  std::vector<std::thread> threads;
46  for (int i = 0; i < kNumThreads - 1; ++i) {
47  threads.push_back(std::thread(thread_func));
48  }
49 
50  // Give (kNumThreads - 1) threads a chance to reach the barrier.
51  // This test assumes at least one thread will have run after the
52  // sleep has elapsed. Sleeping in a test is usually bad form, but we
53  // need to make sure that we are testing the barrier instead of some
54  // other synchronization method.
56 
57  // The counter should still be zero since no thread should have
58  // been able to pass the barrier yet.
59  {
60  absl::MutexLock lock(&mutex);
61  EXPECT_EQ(counter, 0);
62  }
63 
64  // Start 1 more thread. This should make all threads pass the barrier.
65  threads.push_back(std::thread(thread_func));
66 
67  // All threads should now be able to proceed and finish.
68  for (auto& thread : threads) {
69  thread.join();
70  }
71 
72  // All threads should now have incremented the counter.
73  absl::MutexLock lock(&mutex);
74  EXPECT_EQ(counter, kNumThreads);
75 }
void SleepFor(absl::Duration duration)
Definition: clock.h:68
int * counter
TEST(Barrier, SanityTest)
Definition: barrier_test.cc:25
bool Block()
Definition: barrier.cc:27
constexpr Duration Seconds(int64_t n)
Definition: time.h:1461
constexpr int32_t kNumThreads


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autogenerated on Tue Jun 18 2019 19:44:35