/*
    * Copyright (C) 2011 The Guava 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
    *
    * 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.
   */
  
  package com.google.common.util.concurrent;
  
  import com.google.caliper.BeforeExperiment;
  import com.google.caliper.Benchmark;
  import com.google.caliper.Param;
  
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  /**
   * Benchmarks for {@link CycleDetectingLockFactory}.
   *
   * @author Darick Tong
   */
  public class CycleDetectingLockFactoryBenchmark {
  
    @Param({"2","3","4","5","10"}) int lockNestingDepth;
  
    CycleDetectingLockFactory factory;
    private Lock[] plainLocks;
    private Lock[] detectingLocks;
  
    @BeforeExperiment
    void setUp() throws Exception {
      this.factory = CycleDetectingLockFactory.newInstance(
          CycleDetectingLockFactory.Policies.WARN);
      this.plainLocks = new Lock[lockNestingDepth];
      for (int i = 0; i < lockNestingDepth; i++) {
        plainLocks[i] = new ReentrantLock();
      }
      this.detectingLocks = new Lock[lockNestingDepth];
      for (int i = 0; i < lockNestingDepth; i++) {
        detectingLocks[i] = factory.newReentrantLock("Lock" + i);
      }
    }
  
    @Benchmark void unorderedPlainLocks(int reps) {
      lockAndUnlock(new ReentrantLock(), reps);
    }
  
    @Benchmark void unorderedCycleDetectingLocks(int reps) {
      lockAndUnlock(factory.newReentrantLock("foo"), reps);
    }
  
    private void lockAndUnlock(Lock lock, int reps) {
      for (int i = 0; i < reps; i++) {
        lock.lock();
        lock.unlock();
      }
    }
  
    @Benchmark void orderedPlainLocks(int reps) {
      lockAndUnlockNested(plainLocks, reps);
    }
  
    @Benchmark void orderedCycleDetectingLocks(int reps) {
      lockAndUnlockNested(detectingLocks, reps);
    }
  
    private void lockAndUnlockNested(Lock[] locks, int reps) {
      for (int i = 0; i < reps; i++) {
        for (int j = 0; j < locks.length; j++) {
          locks[j].lock();
        }
        for (int j = locks.length - 1; j >= 0; j--) {
          locks[j].unlock();
        }
      }
    }
  }