org.apache.giraph.examples.okapi.common.computation.SendFriends.java Source code

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Here is the source code for org.apache.giraph.examples.okapi.common.computation.SendFriends.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 org.apache.giraph.examples.okapi.common.computation;

import java.io.IOException;

import org.apache.giraph.examples.okapi.common.data.MessageWrapper;

import org.apache.giraph.edge.Edge;
import org.apache.giraph.graph.BasicComputation;
import org.apache.giraph.graph.Vertex;
import org.apache.giraph.utils.ArrayListWritable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableUtils;

/**
 * Many applications require a vertex to send a list of its friends to all
 * its neighbors in the graph. This is common in algorithms that require a
 * vertex to know its 2-hop neighborhood, such as triangle counting or computing
 * the clustering coefficient.
 *
 * Such algorithms can re-use this computation class. They only need to extend
 * it and specify the parameter types.
 *
 * @param <I> Vertex ID
 * @param <V> Vertex value
 * @param <E> Edge value
 * @param <M> Message value
 */
public abstract class SendFriends<I extends WritableComparable, V extends Writable, E extends Writable, M extends MessageWrapper<? extends WritableComparable, ? extends ArrayListWritable>>
        extends BasicComputation<I, V, E, M> {

    @Override
    public void compute(Vertex<I, V, E> vertex, Iterable<M> messages) throws IOException {

        final Vertex<I, V, E> finalVertex = vertex;

        final ArrayListWritable friends = new ArrayListWritable() {
            @Override
            public void setClass() {
                setClass(finalVertex.getId().getClass());
            }
        };

        for (Edge<I, E> edge : vertex.getEdges()) {
            friends.add(WritableUtils.clone(edge.getTargetVertexId(), getConf()));
        }

        MessageWrapper<I, ArrayListWritable<I>> msg = new MessageWrapper<I, ArrayListWritable<I>>() {
            @Override
            public Class getVertexIdClass() {
                return finalVertex.getClass();
            }

            @Override
            public Class getMessageClass() {
                return friends.getClass();
            }
        };

        msg.setSourceId(vertex.getId());
        msg.setMessage(friends);
        sendMessageToAllEdges(vertex, (M) msg);
    }
}