src/main/java/org/apache/giraph/examples/SimplePageRankVertex.java

/*
 * 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 com.google.common.collect.Maps;

import org.apache.giraph.graph.BasicVertex;
import org.apache.giraph.graph.BspUtils;
import org.apache.giraph.graph.LongDoubleFloatDoubleVertex;
import org.apache.giraph.graph.VertexReader;
import org.apache.giraph.graph.VertexWriter;
import org.apache.giraph.graph.WorkerContext;
import org.apache.giraph.lib.TextVertexOutputFormat;
import org.apache.giraph.lib.TextVertexOutputFormat.TextVertexWriter;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.log4j.Logger;

import java.io.IOException;
import java.util.Iterator;
import java.util.Map;

/**
 * Demonstrates the basic Pregel PageRank implementation.
 */
public class SimplePageRankVertex extends LongDoubleFloatDoubleVertex {
    /** Number of supersteps for this test */
    public static final int MAX_SUPERSTEPS = 30;
    /** Logger */
    private static final Logger LOG =
        Logger.getLogger(SimplePageRankVertex.class);

    @Override
    public void compute(Iterator<DoubleWritable> msgIterator) {
        LongSumAggregator sumAggreg = (LongSumAggregator) getAggregator("sum");
        MinAggregator minAggreg = (MinAggregator) getAggregator("min");
        MaxAggregator maxAggreg = (MaxAggregator) getAggregator("max");
        if (getSuperstep() >= 1) {
            double sum = 0;
            while (msgIterator.hasNext()) {
                sum += msgIterator.next().get();
            }
            DoubleWritable vertexValue =
                new DoubleWritable((0.15f / getNumVertices()) + 0.85f * sum);
            setVertexValue(vertexValue);
            maxAggreg.aggregate(vertexValue);
            minAggreg.aggregate(vertexValue);
            sumAggreg.aggregate(1L);
            LOG.info(getVertexId() + ": PageRank=" + vertexValue +
                     " max=" + maxAggreg.getAggregatedValue() +
                     " min=" + minAggreg.getAggregatedValue());
        }

        if (getSuperstep() < MAX_SUPERSTEPS) {
            long edges = getNumOutEdges();
            sendMsgToAllEdges(
                new DoubleWritable(getVertexValue().get() / edges));
        } else {
            voteToHalt();
        }
    }

	public static class SimplePageRankVertexWorkerContext extends
    		WorkerContext {

    	public static double finalMax, finalMin;
    	public static long finalSum;
    	
    	@Override
    	public void preApplication() 
    	throws InstantiationException, IllegalAccessException {
    		
    		registerAggregator("sum", LongSumAggregator.class);
    		registerAggregator("min", MinAggregator.class);
    		registerAggregator("max", MaxAggregator.class);			
    	}

    	@Override
    	public void postApplication() {

    		LongSumAggregator sumAggreg = 
    			(LongSumAggregator) getAggregator("sum");
    		MinAggregator minAggreg = 
    			(MinAggregator) getAggregator("min");
    		MaxAggregator maxAggreg = 
    			(MaxAggregator) getAggregator("max");

    		finalSum = sumAggreg.getAggregatedValue().get();
    		finalMax = maxAggreg.getAggregatedValue().get();
    		finalMin = minAggreg.getAggregatedValue().get();
    		
            LOG.info("aggregatedNumVertices=" + finalSum);
            LOG.info("aggregatedMaxPageRank=" + finalMax);
            LOG.info("aggregatedMinPageRank=" + finalMin);
    	}

		@Override
		public void preSuperstep() {
    		
	        LongSumAggregator sumAggreg = 
	        	(LongSumAggregator) getAggregator("sum");
	        MinAggregator minAggreg = 
	        	(MinAggregator) getAggregator("min");
	        MaxAggregator maxAggreg = 
	        	(MaxAggregator) getAggregator("max");
	        
	        if (getSuperstep() >= 3) {
	            LOG.info("aggregatedNumVertices=" +
	                    sumAggreg.getAggregatedValue() +
	                    " NumVertices=" + getNumVertices());
	            if (sumAggreg.getAggregatedValue().get() != getNumVertices()) {
	                throw new RuntimeException("wrong value of SumAggreg: " +
	                        sumAggreg.getAggregatedValue() + ", should be: " +
	                        getNumVertices());
	            }
	            DoubleWritable maxPagerank =
	                    (DoubleWritable) maxAggreg.getAggregatedValue();
	            LOG.info("aggregatedMaxPageRank=" + maxPagerank.get());
	            DoubleWritable minPagerank =
	                    (DoubleWritable) minAggreg.getAggregatedValue();
	            LOG.info("aggregatedMinPageRank=" + minPagerank.get());
	        }
	        useAggregator("sum");
	        useAggregator("min");
	        useAggregator("max");
	        sumAggreg.setAggregatedValue(new LongWritable(0L));
		}

		@Override
		public void postSuperstep() { }
    }
    
    /**
     * Simple VertexReader that supports {@link SimplePageRankVertex}
     */
    public static class SimplePageRankVertexReader extends
            GeneratedVertexReader<LongWritable, DoubleWritable, FloatWritable,
                DoubleWritable> {
        /** Class logger */
        private static final Logger LOG =
            Logger.getLogger(SimplePageRankVertexReader.class);

        public SimplePageRankVertexReader() {
            super();
        }

        @Override
        public boolean nextVertex() {
            return totalRecords > recordsRead;
        }

        @Override
        public BasicVertex<LongWritable, DoubleWritable, FloatWritable, DoubleWritable>
          getCurrentVertex() throws IOException {
            BasicVertex<LongWritable, DoubleWritable, FloatWritable, DoubleWritable>
                vertex = BspUtils.createVertex(configuration);

            LongWritable vertexId = new LongWritable(
                (inputSplit.getSplitIndex() * totalRecords) + recordsRead);
            DoubleWritable vertexValue = new DoubleWritable(vertexId.get() * 10d);
            long destVertexId =
                (vertexId.get() + 1) %
                (inputSplit.getNumSplits() * totalRecords);
            float edgeValue = vertexId.get() * 100f;
            Map<LongWritable, FloatWritable> edges = Maps.newHashMap();
            edges.put(new LongWritable(destVertexId), new FloatWritable(edgeValue));
            vertex.initialize(vertexId, vertexValue, edges, null);
            ++recordsRead;
            if (LOG.isInfoEnabled()) {
	        LOG.info("next: Return vertexId=" + vertex.getVertexId().get() +
	                 ", vertexValue=" + vertex.getVertexValue() +
	                 ", destinationId=" + destVertexId + ", edgeValue=" + edgeValue);
            }
            return vertex;
        }
    }

    /**
     * Simple VertexInputFormat that supports {@link SimplePageRankVertex}
     */
    public static class SimplePageRankVertexInputFormat extends
            GeneratedVertexInputFormat<LongWritable,
            DoubleWritable, FloatWritable, DoubleWritable> {
        @Override
        public VertexReader<LongWritable, DoubleWritable, FloatWritable, DoubleWritable>
                createVertexReader(InputSplit split,
                                   TaskAttemptContext context)
                                   throws IOException {
            return new SimplePageRankVertexReader();
        }
    }

    /**
     * Simple VertexWriter that supports {@link SimplePageRankVertex}
     */
    public static class SimplePageRankVertexWriter extends
            TextVertexWriter<LongWritable, DoubleWritable, FloatWritable> {
        public SimplePageRankVertexWriter(
                RecordWriter<Text, Text> lineRecordWriter) {
            super(lineRecordWriter);
        }

        @Override
        public void writeVertex(
                BasicVertex<LongWritable, DoubleWritable, FloatWritable, ?> vertex)
                throws IOException, InterruptedException {
            getRecordWriter().write(
                new Text(vertex.getVertexId().toString()),
                new Text(vertex.getVertexValue().toString()));
        }
    }

    /**
     * Simple VertexOutputFormat that supports {@link SimplePageRankVertex}
     */
    public static class SimplePageRankVertexOutputFormat extends
            TextVertexOutputFormat<LongWritable, DoubleWritable, FloatWritable> {

        @Override
        public VertexWriter<LongWritable, DoubleWritable, FloatWritable>
            createVertexWriter(TaskAttemptContext context)
                throws IOException, InterruptedException {
            RecordWriter<Text, Text> recordWriter =
                textOutputFormat.getRecordWriter(context);
            return new SimplePageRankVertexWriter(recordWriter);
        }
    }
}