| /* |
| * 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.hadoop.io.Writable; |
| import org.apache.hadoop.io.WritableComparable; |
| |
| import com.google.common.primitives.UnsignedInts; |
| |
| /** |
| * Divides the vertices into partitions by their hash code using ranges of the |
| * hash space. |
| * |
| * @param <I> Vertex index value |
| * @param <V> Vertex value |
| * @param <E> Edge value |
| */ |
| @SuppressWarnings("rawtypes") |
| public class HashRangePartitionerFactory<I extends WritableComparable, |
| V extends Writable, E extends Writable> |
| extends GraphPartitionerFactory<I, V, E> { |
| |
| /** A transformed hashCode() must be strictly smaller than this. */ |
| private static final long HASH_LIMIT = 2L * Integer.MAX_VALUE + 2L; |
| |
| @Override |
| public int getPartition(I id, int partitionCount, int workerCount) { |
| long unsignedHashCode = UnsignedInts.toLong(id.hashCode()); |
| // The reader can verify that unsignedHashCode of HASH_LIMIT - 1 yields |
| // index of size - 1, and unsignedHashCode of 0 yields index of 0. |
| return (int) ((unsignedHashCode * partitionCount) / HASH_LIMIT); |
| } |
| |
| @Override |
| public int getWorker(int partition, int partitionCount, int workerCount) { |
| return partition % workerCount; |
| } |
| } |