/* Copyright 2015 The TensorFlow Authors. All Rights Reserved.

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 "tensorflow/core/lib/core/threadpool.h"

#include <atomic>

#include "tensorflow/core/platform/env.h"
#include "tensorflow/core/platform/mutex.h"
#include "tensorflow/core/platform/test.h"
#include "tensorflow/core/platform/test_benchmark.h"

namespace tensorflow {
namespace thread {

static const int kNumThreads = 30;

TEST(ThreadPool, Empty) {
  for (int num_threads = 1; num_threads < kNumThreads; num_threads++) {
    fprintf(stderr, "Testing with %d threads\n", num_threads);
    ThreadPool pool(Env::Default(), "test", num_threads);
  }
}

TEST(ThreadPool, DoWork) {
  for (int num_threads = 1; num_threads < kNumThreads; num_threads++) {
    fprintf(stderr, "Testing with %d threads\n", num_threads);
    const int kWorkItems = 15;
    bool work[kWorkItems];
    for (int i = 0; i < kWorkItems; i++) {
      work[i] = false;
    }
    {
      ThreadPool pool(Env::Default(), "test", num_threads);
      for (int i = 0; i < kWorkItems; i++) {
        pool.Schedule([&work, i]() {
          ASSERT_FALSE(work[i]);
          work[i] = true;
        });
      }
    }
    for (int i = 0; i < kWorkItems; i++) {
      ASSERT_TRUE(work[i]);
    }
  }
}

TEST(ThreadPool, ParallelFor) {
  // Make ParallelFor use as many threads as possible.
  int64 kHugeCost = 1 << 30;
  for (int num_threads = 1; num_threads < kNumThreads; num_threads++) {
    fprintf(stderr, "Testing with %d threads\n", num_threads);
    const int kWorkItems = 15;
    bool work[kWorkItems];
    ThreadPool pool(Env::Default(), "test", num_threads);
    for (int i = 0; i < kWorkItems; i++) {
      work[i] = false;
    }
    pool.ParallelFor(kWorkItems, kHugeCost, [&work](int64 begin, int64 end) {
      for (int64 i = begin; i < end; ++i) {
        ASSERT_FALSE(work[i]);
        work[i] = true;
      }
    });
    for (int i = 0; i < kWorkItems; i++) {
      ASSERT_TRUE(work[i]);
    }
  }
}

TEST(ThreadPool, ParallelForWithWorkerId) {
  // Make ParallelForWithWorkerId use as many threads as possible.
  int64 kHugeCost = 1 << 30;
  for (int num_threads = 1; num_threads < kNumThreads; num_threads++) {
    fprintf(stderr, "Testing with %d threads\n", num_threads);
    const int kWorkItems = 15;
    volatile std::atomic<bool> work[kWorkItems];
    ThreadPool pool(Env::Default(), "test", num_threads);
    for (int i = 0; i < kWorkItems; i++) {
      work[i] = false;
    }
    volatile std::atomic<bool> threads_running[kNumThreads + 1];
    for (int i = 0; i < num_threads + 1; i++) {
      threads_running[i] = false;
    }
    pool.ParallelForWithWorkerId(
        kWorkItems, kHugeCost,
        [&threads_running, &work, num_threads](
            int64 begin, int64 end, int64 id) {
          // Store true for the current thread, and assert that another thread
          // is not running with the same id.
          ASSERT_LE(0, id);
          ASSERT_LE(id, kNumThreads);
          ASSERT_FALSE(threads_running[id].exchange(true));
          for (int64 i = begin; i < end; ++i) {
            ASSERT_FALSE(work[i].exchange(true));
          }
          ASSERT_TRUE(threads_running[id].exchange(false));
          threads_running[id] = false;
        });
    for (int i = 0; i < kWorkItems; i++) {
      ASSERT_TRUE(work[i]);
    }
    for (int i = 0; i < num_threads + 1; i++) {
      ASSERT_FALSE(threads_running[i]);
    }
  }
}

static void BM_Sequential(int iters) {
  ThreadPool pool(Env::Default(), "test", kNumThreads);
  // Decrement count sequentially until 0.
  int count = iters;
  mutex done_lock;
  condition_variable done;
  bool done_flag = false;
  std::function<void()> work = [&pool, &count, &done_lock, &done, &done_flag,
                                &work]() {
    if (count--) {
      pool.Schedule(work);
    } else {
      mutex_lock l(done_lock);
      done_flag = true;
      done.notify_all();
    }
  };
  work();
  mutex_lock l(done_lock);
  if (!done_flag) {
    done.wait(l);
  }
}
BENCHMARK(BM_Sequential);

static void BM_Parallel(int iters) {
  ThreadPool pool(Env::Default(), "test", kNumThreads);
  // Decrement count concurrently until 0.
  std::atomic_int_fast32_t count(iters);
  mutex done_lock;
  condition_variable done;
  bool done_flag = false;
  for (int i = 0; i < iters; ++i) {
    pool.Schedule([&count, &done_lock, &done, &done_flag]() {
      if (count.fetch_sub(1) == 1) {
        mutex_lock l(done_lock);
        done_flag = true;
        done.notify_all();
      }
    });
  }
  mutex_lock l(done_lock);
  if (!done_flag) {
    done.wait(l);
  }
}
BENCHMARK(BM_Parallel);

}  // namespace thread
}  // namespace tensorflow
