| /* |
| * 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 org.apache.hadoop.io.IntWritable; |
| import org.apache.hadoop.io.NullWritable; |
| |
| import com.google.common.collect.UnmodifiableIterator; |
| |
| 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.Collection; |
| import java.util.Iterator; |
| |
| /** |
| * 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> { |
| /** Array of target vertex ids */ |
| private IntArrayList neighbors; |
| |
| @Override |
| public void initialize(Iterable<Edge<IntWritable, NullWritable>> edges) { |
| // If the iterable is actually a collection, we can cheaply get the |
| // size and initialize the array with the expected capacity. |
| if (edges instanceof Collection) { |
| int numEdges = |
| ((Collection<Edge<IntWritable, NullWritable>>) edges).size(); |
| initialize(numEdges); |
| } else { |
| initialize(); |
| } |
| for (Edge<IntWritable, NullWritable> edge : edges) { |
| add(edge); |
| } |
| } |
| |
| @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.get(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 IntIterator neighborsIt = neighbors.iterator(); |
| /** Representative edge object. */ |
| private 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()); |
| } |
| } |
| } |