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

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Here is the source code for org.apache.giraph.edge.LongNullHashSetEdges.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 it.unimi.dsi.fastutil.longs.LongIterator;
import it.unimi.dsi.fastutil.longs.LongOpenHashSet;

import org.apache.giraph.utils.EdgeIterables;
import org.apache.giraph.utils.Trimmable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;

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

/**
 * {@link OutEdges} implementation with long ids and null edge values,
 * backed by a {@link LongOpenHashSet}.
 * Parallel edges are not allowed.
 * Note: this implementation is optimized for fast random access and mutations,
 * and uses less space than a generic {@link HashMapEdges} (but more than
 * {@link LongNullArrayEdges}.
 */
public class LongNullHashSetEdges
        implements ReuseObjectsOutEdges<LongWritable, NullWritable>, MutableOutEdges<LongWritable, NullWritable>,
        StrictRandomAccessOutEdges<LongWritable, NullWritable>, Trimmable {
    /** Hash set of target vertex ids. */
    private LongOpenHashSet neighbors;

    @Override
    public void initialize(Iterable<Edge<LongWritable, NullWritable>> edges) {
        EdgeIterables.initialize(this, edges);
    }

    @Override
    public void initialize(int capacity) {
        neighbors = new LongOpenHashSet(capacity);
    }

    @Override
    public void initialize() {
        neighbors = new LongOpenHashSet();
    }

    @Override
    public void add(Edge<LongWritable, NullWritable> edge) {
        neighbors.add(edge.getTargetVertexId().get());
    }

    @Override
    public void remove(LongWritable targetVertexId) {
        neighbors.remove(targetVertexId.get());
    }

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

    @Override
    public Iterator<Edge<LongWritable, NullWritable>> iterator() {
        // Returns an iterator that reuses objects.
        // The downcast is fine because all concrete Edge implementations are
        // mutable, but we only expose the mutation functionality when appropriate.
        return (Iterator) mutableIterator();
    }

    @Override
    public Iterator<MutableEdge<LongWritable, NullWritable>> mutableIterator() {
        return new Iterator<MutableEdge<LongWritable, NullWritable>>() {
            /** Wrapped neighbors iterator. */
            private LongIterator neighborsIt = neighbors.iterator();
            /** Representative edge object. */
            private ReusableEdge<LongWritable, NullWritable> representativeEdge = EdgeFactory
                    .createReusable(new LongWritable());

            public boolean hasNext() {
                return neighborsIt.hasNext();
            }

            @Override
            public MutableEdge<LongWritable, NullWritable> next() {
                representativeEdge.getTargetVertexId().set(neighborsIt.nextLong());
                return representativeEdge;
            }

            @Override
            public void remove() {
                neighborsIt.remove();
            }
        };
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeInt(neighbors.size());
        LongIterator neighborsIt = neighbors.iterator();
        while (neighborsIt.hasNext()) {
            out.writeLong(neighborsIt.nextLong());
        }
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        int numEdges = in.readInt();
        initialize(numEdges);
        for (int i = 0; i < numEdges; ++i) {
            neighbors.add(in.readLong());
        }
    }

    @Override
    public NullWritable getEdgeValue(LongWritable targetVertexId) {
        if (neighbors.contains(targetVertexId.get())) {
            return NullWritable.get();
        } else {
            return null;
        }
    }

    @Override
    public void setEdgeValue(LongWritable targetVertexId, NullWritable edgeValue) {
        // No operation.
        // Only set value for an existing edge.
        // If the edge exist, the Null value is already there.
    }

    @Override
    public void trim() {
        neighbors.trim();
    }
}