Java tutorial
/* * Copyright (C) IBM Corp. 2009. * * Licensed 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.sf.xrime.algorithms.partitions.connected.strongly; import java.io.IOException; import java.util.HashSet; import java.util.Iterator; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.compress.GzipCodec; import org.apache.hadoop.mapred.FileInputFormat; import org.apache.hadoop.mapred.FileOutputFormat; import org.apache.hadoop.mapred.JobClient; import org.apache.hadoop.mapred.JobConf; import org.apache.hadoop.mapred.Mapper; import org.apache.hadoop.mapred.OutputCollector; import org.apache.hadoop.mapred.Reducer; import org.apache.hadoop.mapred.Reporter; import org.apache.hadoop.mapred.SequenceFileInputFormat; import org.apache.hadoop.mapred.SequenceFileOutputFormat; import org.sf.xrime.ProcessorExecutionException; import org.sf.xrime.algorithms.GraphAlgorithm; import org.sf.xrime.algorithms.utils.GraphAlgorithmMapReduceBase; import org.sf.xrime.model.edge.AdjVertexEdge; import org.sf.xrime.model.vertex.LabeledAdjBiSetVertex; /** * The backward trim is to trim vertexes which have no descendants. This class is used to * do the real trim. * @author xue * */ public class BackwardTrimPartB extends GraphAlgorithm { /** * Default constructor. */ public BackwardTrimPartB() { super(); } /** * Mapper. * @author xue */ public static class MapClass extends GraphAlgorithmMapReduceBase implements Mapper<Text, LabeledAdjBiSetVertex, Text, LabeledAdjBiSetVertex> { @Override public void map(Text key, LabeledAdjBiSetVertex value, OutputCollector<Text, LabeledAdjBiSetVertex> output, Reporter reporter) throws IOException { if (value.getForwardVertexes() == null || value.getForwardVertexes().size() == 0) { // This vertex does not have descendants. Trim it and all its edges. So we need // to notify all its immediate ancestors. for (AdjVertexEdge ancestor : value.getBackwardVertexes()) { LabeledAdjBiSetVertex notifier = new LabeledAdjBiSetVertex(); notifier.setId(ancestor.getOpposite()); notifier.setStringLabel(ConstantLabels.DESCENDANT_TO_BE_REMOVED, value.getId()); // Tell the ancestor that this vertex is to be removed. output.collect(new Text(ancestor.getOpposite()), notifier); } } else { // Normal vertex, emit it. output.collect(key, value); } } } /** * Reducer. * @author xue */ public static class ReduceClass extends GraphAlgorithmMapReduceBase implements Reducer<Text, LabeledAdjBiSetVertex, Text, LabeledAdjBiSetVertex> { @Override public void reduce(Text key, Iterator<LabeledAdjBiSetVertex> values, OutputCollector<Text, LabeledAdjBiSetVertex> output, Reporter reporter) throws IOException { // The descendants to be removed. HashSet<String> descendants_to_be_removed = new HashSet<String>(); LabeledAdjBiSetVertex ancestor = null; while (values.hasNext()) { LabeledAdjBiSetVertex curr_vertex = values.next(); if (curr_vertex.getStringLabel(ConstantLabels.DESCENDANT_TO_BE_REMOVED) == null) { // Clone this vertex for later use. NOT deep clone. ancestor = new LabeledAdjBiSetVertex(curr_vertex); } else { // This vertex has some descendants to be removed. descendants_to_be_removed .add(curr_vertex.getStringLabel(ConstantLabels.DESCENDANT_TO_BE_REMOVED)); } } if (ancestor != null) { for (String descendant : descendants_to_be_removed) { // Remove edges to descendants to be removed. ancestor.getForwardVertexes().remove(new AdjVertexEdge(descendant)); } output.collect(key, ancestor); } } } @Override public void execute() throws ProcessorExecutionException { JobConf conf = new JobConf(context, BackwardTrimPartB.class); conf.setJobName("BackwardTrimPartB"); // the keys are vertex identifiers (strings) conf.setOutputKeyClass(Text.class); // the values are vertexes (Writable) conf.setOutputValueClass(LabeledAdjBiSetVertex.class); conf.setMapperClass(MapClass.class); // No combiner is permitted. conf.setReducerClass(ReduceClass.class); // makes the file format suitable for machine processing. conf.setInputFormat(SequenceFileInputFormat.class); conf.setOutputFormat(SequenceFileOutputFormat.class); try { FileInputFormat.setInputPaths(conf, getSource().getPath()); FileOutputFormat.setOutputPath(conf, getDestination().getPath()); } catch (IllegalAccessException e1) { throw new ProcessorExecutionException(e1); } conf.setNumMapTasks(getMapperNum()); conf.setNumReduceTasks(getReducerNum()); conf.setMapOutputCompressorClass(GzipCodec.class); conf.setCompressMapOutput(true); try { this.runningJob = JobClient.runJob(conf); } catch (IOException e) { throw new ProcessorExecutionException(e); } } }