Mahout minhash org.apache.hadoop.io.LongWritable 不能转换为 org.apache.hadoop.io.Text答案

【问题标题】：Mahout minhash org.apache.hadoop.io.LongWritable cannot be cast to org.apache.hadoop.io.TextMahout minhash org.apache.hadoop.io.LongWritable 不能转换为 org.apache.hadoop.io.Text
【发布时间】：2013-09-14 20:45:29
【问题描述】：

我正在使用：

hadoop-1.2.1 和 mahout-distribution-0.8

当我尝试使用以下命令运行 HASHMIN 方法时：

$MAHOUT_HOME/bin/mahout org.apache.mahout.clustering.minhash.MinHashDriver -i tce-data/cv.vec -o tce-data/out/cv/minHashDriver/ -ow

我收到此错误：

tce@osy-Inspiron-N5110:~$ $MAHOUT_HOME/bin/mahout org.apache.mahout.clustering.minhash.MinHashDriver  -i  tce-data/cv.vec  -o tce-data/out/cv/minHashDriver/ -ow
Warning: $HADOOP_HOME is deprecated.

Running on hadoop, using /home/tce/app/hadoop-1.2.1/bin/hadoop and HADOOP_CONF_DIR=
MAHOUT-JOB: /home/tce/app/mahout-distribution-0.8/mahout-examples-0.8-job.jar
Warning: $HADOOP_HOME is deprecated.

13/09/10 18:17:46 WARN driver.MahoutDriver: No org.apache.mahout.clustering.minhash.MinHashDriver.props found on classpath, will use command-line arguments only
13/09/10 18:17:46 INFO common.AbstractJob: Command line arguments: {--endPhase=[2147483647], --hashType=[MURMUR], --input=[tce-data/cv.vec], --keyGroups=[2], --minClusterSize=[10], --minVectorSize=[5], --numHashFunctions=[10], --numReducers=[2], --output=[tce-data/out/cv/minHashDriver/], --overwrite=null, --startPhase=[0], --tempDir=[temp], --vectorDimensionToHash=[value]}
13/09/10 18:17:48 INFO input.FileInputFormat: Total input paths to process : 1
13/09/10 18:17:50 INFO mapred.JobClient: Running job: job_201309101645_0031
13/09/10 18:17:51 INFO mapred.JobClient:  map 0% reduce 0%
13/09/10 18:18:27 INFO mapred.JobClient: Task Id : attempt_201309101645_0031_m_000000_0, Status : FAILED
java.lang.ClassCastException: org.apache.hadoop.io.LongWritable cannot be cast to org.apache.hadoop.io.Text
    at org.apache.mahout.clustering.minhash.MinHashMapper.map(MinHashMapper.java:30)
    at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:764)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:364)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
    at org.apache.hadoop.mapred.Child.main(Child.java:249)

我很感激任何想法

【问题讨论】：

stackoverflow.com/questions/14922087/…stackoverflow.com/questions/11784729/…
谢谢@Sandip，但现在我没有自定义编程，我只是在做例子，也许版本有问题。

标签： hadoop mahout minhash

【解决方案1】：

然后交叉检查几件事，你的job.setOutputKeyClass、job.setOutputValueClass、job.setMapOutputKeyClass和job.setMapOutputValueClass应该分别与reducer key、reducer value、mapper key和mapper value类匹配。

您的堆栈跟踪显示Mapper 不匹配。你的MinHashMapper 应该扩展Mapper<[A, B, C, D >] 其中C 和D 与job.setMapOutputKeyClass(C) 和job.setMapOutputValueClass(D) 相同

【讨论】：