/*
    * 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 java.util.ArrayList;
  import java.util.LinkedList;
  
  /**
   * Tests the speed of iteration of different iteration methods for collections.
   * 
   * @author David Richter
   */
  public class IteratorBenchmark {
    @Param({"0", "1", "16", "256", "4096", "65536"}) int size;
  
    // use concrete classes to remove any possible polymorphic overhead?
    Object[] array;
    ArrayList<Object> arrayList;
    LinkedList<Object> linkedList;
  
    @BeforeExperiment void setUp() {
      array = new Object[size];
      arrayList = Lists.newArrayListWithCapacity(size);
      linkedList = Lists.newLinkedList();
  
      for (int i = 0; i < size; i++) {
        Object value = new Object();
        array[i] = value;
        arrayList.add(value);
        linkedList.add(value);
      }
    }
  
    @Benchmark int arrayIndexed(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (int index = 0; index < size; index++) {
          sum += array[index].hashCode();
        }
      }
      return sum;
    }
  
    @Benchmark int arrayIndexedLength(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (int index = 0; index < array.length; index++) {
          sum += array[index].hashCode();
        }
      }
      return sum;
    }
  
    @Benchmark int arrayFor(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (Object value : array) {
          sum += value.hashCode();
        }
      }
      return sum;
    }
  
    @Benchmark int arrayListIndexed(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (int index = 0; index < size; index++) {
          sum += arrayList.get(index).hashCode();
        }
      }
      return sum;
    }
  
    @Benchmark int arrayListIndexedLength(int reps) {
      int sum = 0;
      for (int i = 0; i < reps; i++) {
        for (int index = 0; index < arrayList.size(); index++) {
          sum += arrayList.get(index).hashCode();
        }
      }
      return sum;
   }
 
   @Benchmark int arrayListFor(int reps) {
     int sum = 0;
     for (int i = 0; i < reps; i++) {
       for (Object value : arrayList) {
         sum += value.hashCode();
       }
     }
     return sum;
   }
 
   @Benchmark int arrayListToArrayFor(int reps) {
     int sum = 0;
     for (int i = 0; i < reps; i++) {
       for (Object value : arrayList.toArray()) {
         sum += value.hashCode();
       }
     }
     return sum;
   }
 
   @Benchmark int linkedListFor(int reps) {
     int sum = 0;
     for (int i = 0; i < reps; i++) {
       for (Object value : linkedList) {
         sum += value.hashCode();
       }
     }
     return sum;
   }
 
   @Benchmark int linkedListToArrayFor(int reps) {
     int sum = 0;
     for (int i = 0; i < reps; i++) {
       for (Object value : linkedList.toArray()) {
         sum += value.hashCode();
       }
     }
     return sum;
   }
 }