bookExamples.ch4.algorithms.PageRankVertexComputation.java Source code

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Here is the source code for bookExamples.ch4.algorithms.PageRankVertexComputation.java

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/*
 * 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 bookExamples.ch4.algorithms;

import java.io.IOException;

import org.apache.giraph.graph.BasicComputation;
import org.apache.giraph.graph.Vertex;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;

public class PageRankVertexComputation
        extends BasicComputation<LongWritable, DoubleWritable, NullWritable, DoubleWritable> {

    public static final int MAX_SUPERSTEPS = 5;

    @Override
    public void compute(Vertex<LongWritable, DoubleWritable, NullWritable> vertex,
            Iterable<DoubleWritable> messages) throws IOException {

        if (getSuperstep() >= 1) {
            double sum = 0;
            for (DoubleWritable message : messages) {
                sum += message.get();
            }
            DoubleWritable vertexValue = new DoubleWritable(0.15f / getTotalNumVertices() + 0.85f * sum);
            vertex.setValue(vertexValue);
        }

        if (getSuperstep() < MAX_SUPERSTEPS) {
            long edges = vertex.getNumEdges();
            sendMessageToAllEdges(vertex, new DoubleWritable(vertex.getValue().get() / edges));
        } else {
            vertex.voteToHalt();
        }
    }
}