/*

  * 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 org.apache.giraph.conf.DefaultImmutableClassesGiraphConfigurable;

 import org.apache.giraph.worker.LocalData;

 import org.apache.hadoop.io.Writable;

 import org.apache.hadoop.io.WritableComparable;

 /**

  * Defines the partitioning framework for this application.

  *

  * Abstracts and implements all GraphPartitionerFactoryInterface logic

  * on top of two functions which define partitioning scheme:

  * - which partition vertex should be in, and

  * - which partition should belong to which worker

  *

  * @param <I> Vertex id value

  * @param <V> Vertex value

  * @param <E> Edge value

  */

 @SuppressWarnings("rawtypes")

 public abstract class GraphPartitionerFactory<I extends WritableComparable,

     V extends Writable, E extends Writable>

     extends DefaultImmutableClassesGiraphConfigurable<I, V, E>

     implements GraphPartitionerFactoryInterface<I, V, E>  {

   @Override

   public void initialize(LocalData<I, V, E, ? extends Writable> localData) {

   }

   @Override

   public final MasterGraphPartitioner<I, V, E> createMasterGraphPartitioner() {

     return new MasterGraphPartitionerImpl<I, V, E>(getConf()) {

       @Override

       protected int getWorkerIndex(int partition, int partitionCount,

           int workerCount) {

         return GraphPartitionerFactory.this.getWorker(

             partition, partitionCount, workerCount);

       }

     };

   }

   @Override

   public final WorkerGraphPartitioner<I, V, E> createWorkerGraphPartitioner() {

     return new WorkerGraphPartitionerImpl<I, V, E>() {

       @Override

       protected int getPartitionIndex(I id, int partitionCount,

         int workerCount) {

         return GraphPartitionerFactory.this.getPartition(id,

             partitionCount, workerCount);

       }

     };

   }

   /**

    * Calculates in which partition current vertex belongs to,

    * from interval [0, partitionCount).

    *

    * @param id Vertex id

    * @param partitionCount Number of partitions

    * @param workerCount Number of workers

    * @return partition

    */

   public abstract int getPartition(I id, int partitionCount,

     int workerCount);

   /**

    * 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

    */

   public abstract int getWorker(

       int partition, int partitionCount, int workerCount);

   /**

    * Utility function for calculating in which partition value

    * from interval [0, max) should belong to.

    *

    * @param value Value for which partition is requested

    * @param max Maximum possible value

    * @param partitions Number of partitions, equally sized.

    * @return Index of partition where value belongs to.

    */

   public static int getPartitionInRange(int value, int max, int partitions) {

     double keyRange = ((double) max) / partitions;

     int part = (int) ((value % max) / keyRange);

     return Math.max(0, Math.min(partitions - 1, part));

   }

   /**

    * Utility function for calculating in which partition value

    * from interval [0, max) should belong to.

    *

    * @param value Value for which partition is requested

    * @param max Maximum possible value

    * @param partitions Number of partitions, equally sized.

    * @return Index of partition where value belongs to.

    */

   public static int getPartitionInRange(long value, long max, int partitions) {

     double keyRange = ((double) max) / partitions;

     int part = (int) ((value % max) / keyRange);

     return Math.max(0, Math.min(partitions - 1, part));

   }

 }