| /* |
| * 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.examples; |
| |
| import org.apache.giraph.conf.LongConfOption; |
| import org.apache.giraph.edge.Edge; |
| import org.apache.giraph.graph.Vertex; |
| import org.apache.hadoop.io.DoubleWritable; |
| import org.apache.hadoop.io.FloatWritable; |
| import org.apache.hadoop.io.LongWritable; |
| import org.apache.log4j.Logger; |
| |
| /** |
| * Demonstrates the basic Pregel shortest paths implementation. |
| */ |
| @Algorithm( |
| name = "Shortest paths", |
| description = "Finds all shortest paths from a selected vertex" |
| ) |
| public class SimpleShortestPathsVertex extends |
| Vertex<LongWritable, DoubleWritable, |
| FloatWritable, DoubleWritable> { |
| /** The shortest paths id */ |
| public static final LongConfOption SOURCE_ID = |
| new LongConfOption("SimpleShortestPathsVertex.sourceId", 1); |
| /** Class logger */ |
| private static final Logger LOG = |
| Logger.getLogger(SimpleShortestPathsVertex.class); |
| |
| /** |
| * Is this vertex the source id? |
| * |
| * @return True if the source id |
| */ |
| private boolean isSource() { |
| return getId().get() == SOURCE_ID.get(getConf()); |
| } |
| |
| @Override |
| public void compute(Iterable<DoubleWritable> messages) { |
| if (getSuperstep() == 0) { |
| setValue(new DoubleWritable(Double.MAX_VALUE)); |
| } |
| double minDist = isSource() ? 0d : Double.MAX_VALUE; |
| for (DoubleWritable message : messages) { |
| minDist = Math.min(minDist, message.get()); |
| } |
| if (LOG.isDebugEnabled()) { |
| LOG.debug("Vertex " + getId() + " got minDist = " + minDist + |
| " vertex value = " + getValue()); |
| } |
| if (minDist < getValue().get()) { |
| setValue(new DoubleWritable(minDist)); |
| for (Edge<LongWritable, FloatWritable> edge : getEdges()) { |
| double distance = minDist + edge.getValue().get(); |
| if (LOG.isDebugEnabled()) { |
| LOG.debug("Vertex " + getId() + " sent to " + |
| edge.getTargetVertexId() + " = " + distance); |
| } |
| sendMessage(edge.getTargetVertexId(), new DoubleWritable(distance)); |
| } |
| } |
| voteToHalt(); |
| } |
| } |