/*

  * 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.GiraphConstants;

 import org.apache.giraph.conf.ImmutableClassesGiraphConfiguration;

 import org.apache.hadoop.io.LongWritable;

 import org.apache.hadoop.io.Writable;

 /**

  * Factory for simple range-based partitioners based on long vertex ids.

  * Workers are assigned equal-sized ranges of partitions,

  * and partitions are assigned equal-sized ranges of vertices.

  *

  * @param <V> Vertex value type

  * @param <E> Edge value type

  */

 public class SimpleLongRangePartitionerFactory<V extends Writable,

   E extends Writable> extends GraphPartitionerFactory<LongWritable, V, E> {

   /** Vertex key space size. */

   private long keySpaceSize;

   @Override

   public int getPartition(LongWritable id, int partitionCount,

     int workerCount) {

     return getPartition(id, partitionCount);

   }

   /**

    * Calculates in which partition current vertex belongs to,

    * from interval [0, partitionCount).

    *

    * @param id Vertex id

    * @param partitionCount Number of partitions

    * @return partition

    */

   protected int getPartition(LongWritable id, int partitionCount) {

     return getPartitionInRange(id.get(), keySpaceSize, partitionCount);

   }

   @Override

   public int getWorker(int partition, int partitionCount, int workerCount) {

     return getPartitionInRange(partition, partitionCount, workerCount);

   }

   @Override

   public void setConf(ImmutableClassesGiraphConfiguration conf) {

     super.setConf(conf);

     keySpaceSize =

           conf.getLong(GiraphConstants.PARTITION_VERTEX_KEY_SPACE_SIZE, -1);

     if (keySpaceSize == -1) {

       throw new IllegalStateException("Need to specify " +

           GiraphConstants.PARTITION_VERTEX_KEY_SPACE_SIZE +

           " when using SimpleLongRangePartitionerFactory");

     }

   }

 }