/*
    * 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.cache;
  
  import static com.google.common.base.Preconditions.checkState;
  
  import com.google.caliper.BeforeExperiment;
  import com.google.caliper.Benchmark;
  import com.google.caliper.Param;
  import com.google.common.cache.LocalCache.ReferenceEntry;
  import com.google.common.cache.LocalCache.Segment;
  
  import java.util.concurrent.atomic.AtomicReferenceArray;
  
  /**
   * Benchmark for {@code LocalCache.Segment.expand()}.
   *
   * @author Charles Fry
   */
  public class SegmentBenchmark {
  
    @Param({"16", "32", "64", "128", "256", "512", "1024", "2048", "4096", "8192"}) int capacity;
  
    private Segment<Object, Object> segment;
  
    @BeforeExperiment
    void setUp() {
      LocalCache<Object, Object> cache = new LocalCache<Object, Object>(
          CacheBuilder.newBuilder()
              .concurrencyLevel(1)
              .initialCapacity(capacity), null);
      checkState(cache.segments.length == 1);
      segment = cache.segments[0];
      checkState(segment.table.length() == capacity);
      for (int i = 0; i < segment.threshold; i++) {
        cache.put(new Object(), new Object());
      }
      checkState(segment.table.length() == capacity);
    }
  
    @Benchmark int time(int reps) {
      int dummy = 0;
      AtomicReferenceArray<ReferenceEntry<Object, Object>> oldTable = segment.table;
      for (int i = 0; i < reps; i++) {
        segment.expand();
        segment.table = oldTable;
        dummy += segment.count;
      }
      return dummy;
    }
  }