/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you 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 org.apache.giraph.partition;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.List;

 import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;

 import org.apache.giraph.worker.WorkerInfo;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 import com.google.common.collect.Lists;

 /**

  * Abstracts and implements all MasterGraphPartitioner logic on top of a single

  * user function - getWorkerIndex.

  *

  * @param <I> Vertex id type

  * @param <V> Vertex value type

  * @param <E> Edge value type

  */

 public abstract class MasterGraphPartitionerImpl<I extends WritableComparable,

     V extends Writable, E extends Writable>

     implements MasterGraphPartitioner<I, V, E> {

   /** Provided configuration */

   private final ImmutableClassesGiraphConfiguration<I, V, E> conf;

   /** Save the last generated partition owner list */

   private List<PartitionOwner> partitionOwnerList;

   /**

    * Constructor.

    *

    * @param conf

    *          Configuration used.

    */

   public MasterGraphPartitionerImpl(

       ImmutableClassesGiraphConfiguration<I, V, E> conf) {

     this.conf = conf;

   }

   @Override

   public Collection<PartitionOwner> createInitialPartitionOwners(

       Collection<WorkerInfo> availableWorkerInfos, int maxWorkers) {

     int partitionCount = PartitionUtils.computePartitionCount(

         availableWorkerInfos.size(), conf);

     ArrayList<WorkerInfo> workerList =

         new ArrayList<WorkerInfo>(availableWorkerInfos);

     partitionOwnerList = new ArrayList<PartitionOwner>();

     for (int i = 0; i < partitionCount; i++) {

       partitionOwnerList.add(new BasicPartitionOwner(i, workerList.get(

           getWorkerIndex(i, partitionCount, workerList.size()))));

     }

     return partitionOwnerList;

   }

   @Override

   public void setPartitionOwners(Collection<PartitionOwner> partitionOwners) {

     partitionOwnerList = Lists.newArrayList(partitionOwners);

   }

   @Override

   public Collection<PartitionOwner> generateChangedPartitionOwners(

       Collection<PartitionStats> allPartitionStatsList,

       Collection<WorkerInfo> availableWorkers,

       int maxWorkers,

       long superstep) {

     return PartitionBalancer.balancePartitionsAcrossWorkers(conf,

         partitionOwnerList, allPartitionStatsList, availableWorkers);

   }

   @Override

   public Collection<PartitionOwner> getCurrentPartitionOwners() {

     return partitionOwnerList;

   }

   @Override

   public PartitionStats createPartitionStats() {

     return new PartitionStats();

   }

   /**

    * Calculates worker that should be responsible for passed partition.

    *

    * @param partition Current partition

    * @param partitionCount Number of partitions

    * @param workerCount Number of workers

    * @return index of worker responsible for current partition

    */

   protected abstract int getWorkerIndex(

       int partition, int partitionCount, int workerCount);

 }