| /* |
| * 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.LongArrayList; |
| import it.unimi.dsi.fastutil.longs.LongIterator; |
| 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.Collection; |
| import java.util.Iterator; |
| |
| /** |
| * Implementation of {@link OutEdges} with long ids and null edge |
| * values, backed by a dynamic primitive array. |
| * Parallel edges are allowed. |
| * Note: this implementation is optimized for space usage, |
| * but random access and edge removals are expensive. |
| */ |
| public class LongNullArrayEdges |
| implements ReuseObjectsOutEdges<LongWritable, NullWritable>, |
| MutableOutEdges<LongWritable, NullWritable> { |
| /** Array of target vertex ids. */ |
| private LongArrayList neighbors; |
| |
| @Override |
| public void initialize(Iterable<Edge<LongWritable, NullWritable>> edges) { |
| // If the iterable is actually a collection, we can cheaply get the |
| // size and initialize the arrays with the expected capacity. |
| if (edges instanceof Collection) { |
| int numEdges = |
| ((Collection<Edge<LongWritable, NullWritable>>) edges).size(); |
| initialize(numEdges); |
| } else { |
| initialize(); |
| } |
| for (Edge<LongWritable, NullWritable> edge : edges) { |
| add(edge); |
| } |
| } |
| |
| @Override |
| public void initialize(int capacity) { |
| neighbors = new LongArrayList(capacity); |
| } |
| |
| @Override |
| public void initialize() { |
| neighbors = new LongArrayList(); |
| } |
| |
| @Override |
| public void add(Edge<LongWritable, NullWritable> edge) { |
| neighbors.add(edge.getTargetVertexId().get()); |
| } |
| |
| /** |
| * If the backing array is more than four times as big as the number of |
| * elements, halve its size. |
| */ |
| private void trim() { |
| if (neighbors.elements().length > 4 * neighbors.size()) { |
| neighbors.trim(neighbors.elements().length / 2); |
| } |
| } |
| |
| /** |
| * 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.popLong(); |
| } else { |
| neighbors.set(i, neighbors.popLong()); |
| } |
| // If needed after the removal, trim the array. |
| trim(); |
| } |
| |
| @Override |
| public void remove(LongWritable 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 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>>() { |
| /** Current position in the array. */ |
| private int offset = 0; |
| /** Representative edge object. */ |
| private MutableEdge<LongWritable, NullWritable> representativeEdge = |
| EdgeFactory.createReusable(new LongWritable()); |
| |
| public boolean hasNext() { |
| return offset < neighbors.size(); |
| } |
| |
| @Override |
| public MutableEdge<LongWritable, NullWritable> next() { |
| representativeEdge.getTargetVertexId().set(neighbors.get(offset++)); |
| return representativeEdge; |
| } |
| |
| @Override |
| public void remove() { |
| // Since removeAt() might replace the deleted edge with the last edge |
| // in the array, we need to decrease the offset so that the latter |
| // won't be skipped. |
| removeAt(--offset); |
| } |
| }; |
| } |
| |
| @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()); |
| } |
| } |
| } |
| |