/*
    * Copyright (C) 2010 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.collect;
  
  import com.google.caliper.BeforeExperiment;
  import com.google.caliper.Benchmark;
  import com.google.caliper.Param;
  import com.google.common.base.Preconditions;
  
  import java.util.Random;
  
  /**
   * Tests the speed of iteration of different iteration methods for collections.
   * 
   * @author David Richter
   */
  public class MultisetIteratorBenchmark {
    @Param({"0", "1", "16", "256", "4096", "65536"}) int size;
  
    LinkedHashMultiset<Object> linkedHashMultiset;
    HashMultiset<Object> hashMultiset;
    
    // TreeMultiset requires a Comparable element.
    TreeMultiset<Integer> treeMultiset;
  
    @BeforeExperiment void setUp() {
      hashMultiset = HashMultiset.create(size);
      linkedHashMultiset = LinkedHashMultiset.create(size);
      treeMultiset = TreeMultiset.create();
  
      Random random = new Random();
      
      int sizeRemaining = size;
  
      // TODO(kevinb): generate better test contents for multisets
      for (int i = 0; sizeRemaining > 0; i++) {
        // The JVM will return interned values for small ints.
        Integer value = random.nextInt(1000) + 128;
        int count = Math.min(random.nextInt(10) + 1, sizeRemaining);
        sizeRemaining -= count;
        hashMultiset.add(value, count);
        linkedHashMultiset.add(value, count);
        treeMultiset.add(value, count);
      }
  
      //TODO(kevinb): convert to assert once benchmark tests enable asserts by default    
      Preconditions.checkState(hashMultiset.size() == size);
    }
  
    @Benchmark int hashMultiset(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (Object value : hashMultiset) {
          sum += value.hashCode();
        }
      }
      return sum;
    }
  
    @Benchmark int linkedHashMultiset(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (Object value : linkedHashMultiset) {
          sum += value.hashCode();
        }
      }
      return sum;
    }
  
    @Benchmark int treeMultiset(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (Object value : treeMultiset) {
          sum += value.hashCode();
        }
      }
      return sum;
    }
  }