org.apache.giraph.edge.HashMultimapEdges.java Source code

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Here is the source code for org.apache.giraph.edge.HashMultimapEdges.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.edge;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.UnmodifiableIterator;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

/**
 * {@link OutEdges} implementation backed by an {@link ArrayListMultimap}.
 * Parallel edges are allowed.
 * Note: this implementation is optimized for fast mutations,
 * but uses more space.
 *
 * @param <I> Vertex id
 * @param <E> Edge value
 */
public class HashMultimapEdges<I extends WritableComparable, E extends Writable> extends ConfigurableOutEdges<I, E>
        implements MultiRandomAccessOutEdges<I, E> {
    /** Multimap from target vertex id to edge values. */
    private ArrayListMultimap<I, E> edgeMultimap;

    @Override
    public void initialize(Iterable<Edge<I, E>> edges) {
        // If the iterable is actually a collection, we can cheaply get the
        // size and initialize the hash-multimap with the expected capacity.
        if (edges instanceof Collection) {
            initialize(((Collection<Edge<I, E>>) edges).size());
        } else {
            initialize();
        }
        for (Edge<I, E> edge : edges) {
            add(edge);
        }
    }

    /**
     * Additional initialization method tailored to the underlying multimap
     * implementation.
     *
     * @param expectedNeighbors Expected number of unique neighbors
     * @param expectedEdgesPerNeighbor Expected number of edges per neighbor
     */
    public void initialize(int expectedNeighbors, int expectedEdgesPerNeighbor) {
        edgeMultimap = ArrayListMultimap.create(expectedNeighbors, expectedEdgesPerNeighbor);
    }

    @Override
    public void initialize(int capacity) {
        // To be conservative in terms of space usage, we assume that the initial
        // number of values per key is 1.
        initialize(capacity, 1);
    }

    @Override
    public void initialize() {
        edgeMultimap = ArrayListMultimap.create();
    }

    @Override
    public void add(Edge<I, E> edge) {
        edgeMultimap.put(edge.getTargetVertexId(), edge.getValue());
    }

    @Override
    public void remove(I targetVertexId) {
        edgeMultimap.removeAll(targetVertexId);
    }

    @Override
    public Iterable<E> getAllEdgeValues(I targetVertexId) {
        return edgeMultimap.get(targetVertexId);
    }

    @Override
    public int size() {
        return edgeMultimap.size();
    }

    @Override
    public Iterator<Edge<I, E>> iterator() {
        // Returns an iterator that reuses objects.
        return new UnmodifiableIterator<Edge<I, E>>() {
            /** Wrapped map iterator. */
            private Iterator<Map.Entry<I, E>> mapIterator = edgeMultimap.entries().iterator();
            /** Representative edge object. */
            private ReusableEdge<I, E> representativeEdge = getConf().createReusableEdge();

            @Override
            public boolean hasNext() {
                return mapIterator.hasNext();
            }

            @Override
            public Edge<I, E> next() {
                Map.Entry<I, E> nextEntry = mapIterator.next();
                representativeEdge.setTargetVertexId(nextEntry.getKey());
                representativeEdge.setValue(nextEntry.getValue());
                return representativeEdge;
            }
        };
    }

    @Override
    public void write(DataOutput out) throws IOException {
        // We write both the total number of edges and the number of unique
        // neighbors.
        out.writeInt(edgeMultimap.size());
        out.writeInt(edgeMultimap.keys().size());
        for (Map.Entry<I, E> edge : edgeMultimap.entries()) {
            edge.getKey().write(out);
            edge.getValue().write(out);
        }
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        // Given the total number of pairs and the number of unique neighbors,
        // we are able to compute the average number of edges per neighbors.
        int numEdges = in.readInt();
        int numNeighbors = in.readInt();
        initialize(numEdges, numNeighbors == 0 ? 0 : numEdges / numNeighbors);
        for (int i = 0; i < numEdges; ++i) {
            I targetVertexId = getConf().createVertexId();
            targetVertexId.readFields(in);
            E edgeValue = getConf().createEdgeValue();
            edgeValue.readFields(in);
            edgeMultimap.put(targetVertexId, edgeValue);
        }
    }
}