| /* |
| * 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.edge.Edge; |
| import org.apache.giraph.utils.MathUtils; |
| import org.apache.hadoop.io.DoubleWritable; |
| import org.apache.hadoop.io.LongWritable; |
| import org.apache.hadoop.io.NullWritable; |
| |
| /** |
| * The PageRank algorithm, with uniform transition probabilities on the edges |
| * http://en.wikipedia.org/wiki/PageRank |
| */ |
| public class PageRankVertex extends RandomWalkVertex<NullWritable> { |
| |
| @Override |
| protected double transitionProbability(double stateProbability, |
| Edge<LongWritable, NullWritable> edge) { |
| return stateProbability / getNumEdges(); |
| } |
| |
| @Override |
| protected double recompute(Iterable<DoubleWritable> partialRanks, |
| double teleportationProbability) { |
| |
| // rank contribution from incident neighbors |
| double rankFromNeighbors = MathUtils.sum(partialRanks); |
| // rank contribution from dangling vertices |
| double danglingContribution = |
| getDanglingProbability() / getTotalNumVertices(); |
| |
| // recompute rank |
| return (1d - teleportationProbability) * |
| (rankFromNeighbors + danglingContribution) + |
| teleportationProbability / getTotalNumVertices(); |
| } |
| } |