mahout kmeans 聚类：显示错误

Posted 2023-03-12

【中文标题】mahout kmeans 聚类：显示错误

【英文标题】：mahout kmeans clustering : showing error

【发布时间】：2013-02-22 18:26:45

【问题描述】：

我试图在 mahout 中对数据进行聚类。显示错误。 这是错误

java.lang.ArrayIndexOutOfBoundsException: 0
    at org.apache.mahout.clustering.classify.ClusterClassificationMapper.populateClusterModels(ClusterClassificationMapper.java:129)
    at org.apache.mahout.clustering.classify.ClusterClassificationMapper.setup(ClusterClassificationMapper.java:74)
    at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:142)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:621)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
    at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:177)
13/03/07 19:29:31 INFO mapred.JobClient:  map 0% reduce 0%
13/03/07 19:29:31 INFO mapred.JobClient: Job complete: job_local_0010
13/03/07 19:29:31 INFO mapred.JobClient: Counters: 0
java.lang.InterruptedException: Cluster Classification Driver Job failed processing E:/Thesis/Experiments/Mahout dataset/input
    at org.apache.mahout.clustering.classify.ClusterClassificationDriver.classifyClusterMR(ClusterClassificationDriver.java:276)
    at org.apache.mahout.clustering.classify.ClusterClassificationDriver.run(ClusterClassificationDriver.java:135)
    at org.apache.mahout.clustering.kmeans.KMeansDriver.clusterData(KMeansDriver.java:260)
    at org.apache.mahout.clustering.kmeans.KMeansDriver.run(KMeansDriver.java:152)
    at com.ifm.dataclustering.SequencePrep.<init>(SequencePrep.java:95)
    at com.ifm.dataclustering.App.main(App.java:8)

这是我的代码

Configuration conf = new Configuration();
            FileSystem fs = FileSystem.get(conf);

            Path vector_path = new Path("E:/Thesis/Experiments/Mahout dataset/input/vector_input");
            SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf, vector_path, Text.class, VectorWritable.class);
            VectorWritable vec = new VectorWritable();
            for (NamedVector outputVec : vector) 
                vec.set(outputVec);
                writer.append(new Text(outputVec.getName()), vec);
            
            writer.close();

            // create initial cluster
            Path cluster_path = new Path("E:/Thesis/Experiments/Mahout dataset/clusters/part-00000");
            SequenceFile.Writer cluster_writer = new SequenceFile.Writer(fs, conf, cluster_path, Text.class, Kluster.class);


            // number of cluster k
            int k=4;
            for(i=0;i<k;i++) 
                NamedVector outputVec = vector.get(i);
                Kluster cluster = new Kluster(outputVec, i, new EuclideanDistanceMeasure());
//                System.out.println(cluster);
                cluster_writer.append(new Text(cluster.getIdentifier()), cluster);
                        
            cluster_writer.close();


            // set cluster output path
            Path output = new Path("E:/Thesis/Experiments/Mahout dataset/output");
            HadoopUtil.delete(conf, output);

            KMeansDriver.run(conf, new Path("E:/Thesis/Experiments/Mahout dataset/input"), new Path("E:/Thesis/Experiments/Mahout dataset/clusters"),
                                            output, new EuclideanDistanceMeasure(), 0.001, 10,
                                                            true, 0.0, false);



            SequenceFile.Reader output_reader = new SequenceFile.Reader(fs,new Path("E:/Thesis/Experiments/Mahout dataset/output/" + Kluster.CLUSTERED_POINTS_DIR+ "/part-m-00000"), conf);
            IntWritable key = new IntWritable();
            WeightedVectorWritable value = new WeightedVectorWritable();
            while (output_reader.next(key, value)) 
                System.out.println(value.toString() + " belongs to cluster "
                         + key.toString());
             
            reader.close();

        

【参考方案1】：

输入/输出数据的路径似乎不正确。 MapReduce 作业在集群上运行。因此，数据是从 HDFS 而非本地硬盘读取的。

错误信息：

java.lang.InterruptedException: Cluster Classification Driver Job failed processing E:/Thesis/Experiments/Mahout dataset/input
    at org.apache.mahout.clustering.classify.ClusterClassificationDriver.classifyClusterMR(ClusterClassificationDriver.java:276)

提示您路径不正确。

在运行作业之前，请确保您首先将输入数据上传到 HDFS：

hadoop fs -mkdir input
hadoop fs -copyFromLocal E:\\file input
...

然后代替：

new Path("E:/Thesis/Experiments/Mahout dataset/input")

您应该使用 HDFS 路径：

new Path("input")

或

new Path("/user/<username>/input")

编辑：

使用FileSystem#exists(Path path) 来检查Path 是否有效。

【讨论】：

我改变了路径。但它仍然发现同样的例外。为什么控制台出现arrayIndexOutofBound异常？

我相信每次都会出现异常，kmeans算法的输入是空的。请查看我更新的答案以获取有关如何查找文件系统中是否实际存在路径的指针。

我将输入文件更改为 c:/users// 目录。它有效。