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

Introduction

Here is the source code for org.apache.giraph.edge.IntNullArrayEdges.java

Source

/*
 * 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.ints.IntArrayList;
import it.unimi.dsi.fastutil.ints.IntIterator;

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

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

import com.google.common.collect.UnmodifiableIterator;

/**
 * Implementation of {@link OutEdges} with int ids and null edge
 * values, backed by dynamic primitive array.
 * Parallel edges are allowed.
 * Note: this implementation is optimized for space usage,
 * but edge removals are expensive.
 */
public class IntNullArrayEdges implements ReuseObjectsOutEdges<IntWritable, NullWritable>, Trimmable {
    /** Array of target vertex ids */
    private IntArrayList neighbors;

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

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

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

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

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

    /**
     * Remove edge at position i.
     *
     * @param i Position of edge to be removed
     */
    private void removeAt(int i) {
        // The order of the edges is irrelevant, so we can simply replace
        // the deleted edge with the rightmost element, thus achieving constant
        // time.
        if (i == neighbors.size() - 1) {
            neighbors.popInt();
        } else {
            neighbors.set(i, neighbors.popInt());
        }
    }

    @Override
    public void remove(IntWritable targetVertexId) {
        // Thanks to the constant-time implementation of removeAt(int),
        // we can remove all matching edges in linear time.
        for (int i = neighbors.size() - 1; i >= 0; --i) {
            if (neighbors.getInt(i) == targetVertexId.get()) {
                removeAt(i);
            }
        }
    }

    @Override
    public Iterator<Edge<IntWritable, NullWritable>> iterator() {
        // Returns an iterator that reuses objects.
        return new UnmodifiableIterator<Edge<IntWritable, NullWritable>>() {
            /** Wrapped neighbors iterator. */
            private final IntIterator neighborsIt = neighbors.iterator();
            /** Representative edge object. */
            private final Edge<IntWritable, NullWritable> representativeEdge = EdgeFactory.create(new IntWritable(),
                    NullWritable.get());

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

            @Override
            public Edge<IntWritable, NullWritable> next() {
                representativeEdge.getTargetVertexId().set(neighborsIt.nextInt());
                return representativeEdge;
            }
        };
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeInt(neighbors.size());
        IntIterator iterator = neighbors.iterator();
        while (iterator.hasNext()) {
            out.writeInt(iterator.nextInt());
        }
    }

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

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