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From greghogan <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-2044] [gelly] Implementation of Gelly H...
Date Mon, 02 May 2016 18:26:54 GMT
Github user greghogan commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1956#discussion_r61780238
  
    --- Diff: flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/library/HITSAlgorithm.java
---
    @@ -0,0 +1,194 @@
    +/*
    + * 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.flink.graph.library;
    +
    +import org.apache.flink.api.common.aggregators.DoubleSumAggregator;
    +import org.apache.flink.api.java.DataSet;
    +
    +import org.apache.flink.graph.Edge;
    +import org.apache.flink.graph.EdgeDirection;
    +import org.apache.flink.graph.Graph;
    +import org.apache.flink.graph.GraphAlgorithm;
    +import org.apache.flink.graph.Vertex;
    +import org.apache.flink.graph.spargel.MessageIterator;
    +import org.apache.flink.graph.spargel.MessagingFunction;
    +import org.apache.flink.graph.spargel.ScatterGatherConfiguration;
    +import org.apache.flink.graph.spargel.VertexUpdateFunction;
    +import org.apache.flink.types.DoubleValue;
    +
    +/**
    + * This is an implementation of HITS algorithm, using a scatter-gather iteration.
    + * The user can define the maximum number of iterations. HITS algorithm is determined
by two parameters,
    + * hubs and authorities. A good hub represented a page that pointed to many other pages,
and a good authority
    + * represented a page that was linked by many different hubs. The implementation assumes
that the two value on
    + * every vertex are the same at the beginning.
    + * <p>
    + * If the number of vertices of the input graph is known, it should be provided as a
parameter
    + * to speed up computation. Otherwise, the algorithm will first execute a job to count
the vertices.
    + */
    +public class HITSAlgorithm<K> implements GraphAlgorithm<K, Double, Double, DataSet<Vertex<K,
Double>>> {
    +
    +	public static enum HITSParameter {
    +		HUB,
    +		AUTHORITY
    +	}
    +
    +	private int maxIterations;
    +	private long numberOfVertices;
    +
    +	/**
    +	 * Creates an instance of HITS algorithm.
    +	 * If the number of vertices of the input graph is known,
    +	 * use the {@link HITSAlgorithm#HITSAlgorithm(int, long, HITSParameter)} constructor
instead.
    +	 *
    +	 * @param maxIterations the maximum number of iterations
    +	 * @param hitsParameter the type of final web pages users want to get by this algorithm
    +	 */
    +	public HITSAlgorithm(int maxIterations, HITSParameter hitsParameter) {
    +		if (hitsParameter == HITSParameter.AUTHORITY) {
    +			this.maxIterations = maxIterations * 2;
    +		} else {
    +			this.maxIterations = maxIterations * 2 + 1;
    +		}
    +	}
    +
    +	/**
    +	 * Creates an instance of HITS algorithm.
    +	 * If the number of vertices of the input graph is unknown,
    +	 * use the {@link HITSAlgorithm#HITSAlgorithm(int, HITSParameter)} constructor instead.
    +	 *
    +	 * @param maxIterations the maximum number of iterations
    +	 * @param hitsParameter the type of final web pages users want to get by this algorithm
    +	 */
    +	public HITSAlgorithm(int maxIterations, long numberOfVertices, HITSParameter hitsParameter)
{
    +		if (hitsParameter == HITSParameter.AUTHORITY) {
    +			this.maxIterations = maxIterations * 2;
    +		} else {
    +			this.maxIterations = maxIterations * 2 + 1;
    +		}
    +		this.numberOfVertices = numberOfVertices;
    +	}
    +
    +	@Override
    +	public DataSet<Vertex<K, Double>> run(Graph<K, Double, Double> netGraph)
throws Exception {
    +		if (this.numberOfVertices == 0) {
    +			this.numberOfVertices = netGraph.numberOfVertices();
    +		}
    +
    +		ScatterGatherConfiguration parameter = new ScatterGatherConfiguration();
    +		parameter.setDirection(EdgeDirection.ALL);
    +		parameter.registerAggregator("sumAllValue", new DoubleSumAggregator());
    +
    +		return netGraph.runScatterGatherIteration(new VertexUpdate<K>(maxIterations),
    +				new MessageUpdate<K>(maxIterations), maxIterations, parameter).getVertices();
    +	}
    +
    +	/**
    +	 * Function that updates the value of a vertex by summing up the partial
    +	 * values from all messages and normalize the value.
    +	 */
    +	@SuppressWarnings("serial")
    +	public static final class VertexUpdate<K> extends VertexUpdateFunction<K, Double,
Double> {
    +		private int maxIteration;
    +		private DoubleSumAggregator doubleSumAggregator;
    +
    +		public VertexUpdate(int maxIteration) {
    +			this.maxIteration = maxIteration;
    +		}
    +
    +		@Override
    +		public void preSuperstep() {
    +			doubleSumAggregator = getIterationAggregator("sumAllValue");
    +		}
    +
    +		@Override
    +		public void updateVertex(Vertex<K, Double> vertex, MessageIterator<Double>
inMessages) {
    +			double updateValue = 0;
    +
    +			for (double element : inMessages) {
    +				if (getSuperstepNumber() == maxIteration) {
    +					updateValue = element;
    +					break;
    +				}
    +				updateValue += element;
    +			}
    +
    +			if (getSuperstepNumber() != maxIteration) {
    +				setNewVertexValue(updateValue);
    +				doubleSumAggregator.aggregate(updateValue);
    +			} else {
    +				setNewVertexValue(vertex.getValue() / updateValue);
    +			}
    +		}
    +	}
    +
    +	/**
    +	 * Distributes the value of a vertex among all neighbor vertices and sum all the
    +	 * value in every superstep.
    +	 */
    +	@SuppressWarnings("serial")
    +	public static final class MessageUpdate<K> extends MessagingFunction<K, Double,
Double, Double> {
    +		private int maxIteration;
    +
    +		public MessageUpdate(int maxIteration) {
    +			this.maxIteration = maxIteration;
    +		}
    +
    +		@Override
    +		public void sendMessages(Vertex<K, Double> vertex) {
    +			for (Edge<K, Double> edge : getEdges()) {
    +				if (getSuperstepNumber() % 2 == 1) {
    +					if (edge.getTarget() != vertex.getId()) {
    +						double value = vertex.getValue();
    +
    +						// in the first iteration, no aggregation to call, init sum with value of vertex
    +						double sum = 1;
    +						if (getSuperstepNumber() > 1) {
    +							sum = ((DoubleValue) getPreviousIterationAggregate("sumAllValue")).getValue();
    --- End diff --
    
    We could move this out of the loop.


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