在 mahout-0.6 上的“Mahout in Action”中运行示例代码时出现 IOException

Question

我正在学习 Mahout 并阅读“Mahout in Action”。

当我尝试运行第7章SimpleKMeansClustering.java中的示例代码时，弹出异常：

线程“主”java.io.IOException 中的异常：错误值类：0.0：null 不是类 org.apache.mahout.clustering.WeightedPropertyVectorWritable 在 org.apache.hadoop.io.SequenceFile$Reader.next(SequenceFile .java:1874) 在 SimpleKMeansClustering.main(SimpleKMeansClustering.java:95)

我在 mahout-0.5 上成功执行了这段代码，但在 mahout-0.6 上我看到了这个异常。 即使我将目录名称从 clusters-0 更改为 clusters-0-final，我仍然面临这个异常。

    KMeansDriver.run(conf, vectors, new Path(canopyCentroids, "clusters-0-final"), clusterOutput, new TanimotoDistanceMeasure(), 0.01, 20, true, false);//First, I changed this path.

    SequenceFile.Reader reader = new SequenceFile.Reader(fs,  new Path("output/clusters/clusteredPoints/part-m-00000"), conf);//I double checked this folder and filename.

    IntWritable key = new IntWritable();
    WeightedVectorWritable value = new WeightedVectorWritable();
    int i=0;
    while(reader.next(key, value)) {
        System.out.println(value.toString() + " belongs to cluster " + key.toString());
        i++;
    }
    System.out.println(i);
    reader.close();

有人知道这个例外吗？我一直在尝试解决它很长时间，但没有任何想法。并且互联网上的资源很少。

提前致谢

Answer 1

为了使这个示例在 Mahout 0.6 中工作，添加

import org.apache.mahout.clustering.WeightedPropertyVectorWritable;

导入并替换行：

 WeightedVectorWritable value = new WeightedVectorWritable();

通过

WeightedPropertyVectorWritable value = new WeightedPropertyVectorWritable();

这是因为 Mahout 0.6 代码将聚类输出值写入新类型 WeightedPropertyVectorWritable。

Answer 2

它可能关心的人，这里是 mahout 0.9 的工作 MiA 示例：

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.mahout.clustering.Cluster;
import org.apache.mahout.clustering.classify.WeightedPropertyVectorWritable;
import org.apache.mahout.clustering.kmeans.KMeansDriver;
import org.apache.mahout.clustering.kmeans.Kluster;
import org.apache.mahout.common.distance.EuclideanDistanceMeasure;
import org.apache.mahout.math.RandomAccessSparseVector;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class SimpleKMeansClustering {

    public static final double[][] points = {
            {1, 1}, {2, 1}, {1, 2},
            {2, 2}, {3, 3}, {8, 8},
            {9, 8}, {8, 9}, {9, 9}};

    public static void writePointsToFile(List<Vector> points,
                                         String fileName,
                                         FileSystem fs,
                                         Configuration conf) throws IOException {
        Path path = new Path(fileName);
        SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf,
                path, LongWritable.class, VectorWritable.class);
        long recNum = 0;
        VectorWritable vec = new VectorWritable();
        for (Vector point : points) {
            vec.set(point);
            writer.append(new LongWritable(recNum++), vec);
        }
        writer.close();
    }

    public static List<Vector> getPoints(double[][] raw) {
        List<Vector> points = new ArrayList<Vector>();
        for (int i = 0; i < raw.length; i++) {
            double[] fr = raw[i];
            Vector vec = new RandomAccessSparseVector(fr.length);
            vec.assign(fr);
            points.add(vec);
        }
        return points;
    }

    public static void main(String args[]) throws Exception {

        int k = 2;

        List<Vector> vectors = getPoints(points);

        File testData = new File("clustering/testdata");
        if (!testData.exists()) {
            testData.mkdir();
        }
        testData = new File("clustering/testdata/points");
        if (!testData.exists()) {
            testData.mkdir();
        }

        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(conf);
        writePointsToFile(vectors, "clustering/testdata/points/file1", fs, conf);

        Path path = new Path("clustering/testdata/clusters/part-00000");
        SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf, path, Text.class, Kluster.class);

        for (int i = 0; i < k; i++) {
            Vector vec = vectors.get(i);
            Kluster cluster = new Kluster(vec, i, new EuclideanDistanceMeasure());
            writer.append(new Text(cluster.getIdentifier()), cluster);
        }
        writer.close();

        KMeansDriver.run(conf,
                new Path("clustering/testdata/points"),
                new Path("clustering/testdata/clusters"),
                new Path("clustering/output"),
                0.001,
                10,
                true,
                0,
                true);

        SequenceFile.Reader reader = new SequenceFile.Reader(fs,
                new Path("clustering/output/" + Cluster.CLUSTERED_POINTS_DIR + "/part-m-0"), conf);

        IntWritable key = new IntWritable();
        WeightedPropertyVectorWritable value = new WeightedPropertyVectorWritable();
        while (reader.next(key, value)) {
            System.out.println(value.toString() + " belongs to cluster " + key.toString());
        }
        reader.close();
    }

}

Answer 3

本书中的示例适用于 mahout 05，但有以下小改动：

(1)正确设置路径：

   KMeansDriver.run(conf, new Path("testdata/points"), new Path("testdata/clusters"), new Path("testdata/output"), new EuclideanDistanceMeasure(), 0.001, 10, true, false);

和

   SequenceFile.Reader reader = new SequenceFile.Reader(fs, new Path("testdata/output/clusteredPoints/part-m-0"), conf);

(2) 如果您没有安装 HADOOP，那么您需要将 KMeansDriver.run() 调用的最后一个参数从“false”更改为“true”。

   KMeansDriver.run(conf, new Path("testdata/points"), new Path("testdata/clusters"), new Path("testdata/output"), new EuclideanDistanceMeasure(), 0.001, 10, true, true);

那么这个例子就起作用了。

Answer 4

替换

import org.apache.mahout.clustering.WeightedVectorWritable;

与

import org.apache.mahout.clustering.classify.WeightedVectorWritable;