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https://issues.apache.org/jira/browse/MAHOUT-751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13059022#comment-13059022
]
patrick.J commented on MAHOUT-751:
----------------------------------
You Remind me the key point...Much appreciate(and sorry for place it here,I'll
remember appropriate place next time)
> (Mapreduce)ClassCastException: org.apache.hadoop.io.LongWritable cannot be
> cast to ....io.Text
> ----------------------------------------------------------------------------------------------
>
> Key: MAHOUT-751
> URL: https://issues.apache.org/jira/browse/MAHOUT-751
> Project: Mahout
> Issue Type: Bug
> Components: build
> Environment: ubuntu 10.04/hadoop 0.21.0
> Reporter: patrick.J
> Labels: hadoop
>
> Could somebody help me ?
> My mapreduce program cast a Exception like:
> 11/07/01 20:18:06 INFO mapreduce.Job: Task Id :
> attempt_201107011635_0005_m_000000_0, Status : FAILED
> java.lang.ClassCastException: org.apache.hadoop.io.LongWritable cannot be
> cast to org.apache.hadoop.io.Text
> at Sum$MapClass.map(Sum.java:15)
> at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:144)
> at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:652)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:328)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:217)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:396)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:742)
> at org.apache.hadoop.mapred.Child.main(Child.java:211)
> There's the code:
> import java.io.*;
> import java.util.*;
> import org.apache.hadoop.fs.Path;
> import org.apache.hadoop.conf.*;
> import org.apache.hadoop.io.*;
> import org.apache.hadoop.mapreduce.*;
> import org.apache.hadoop.mapreduce.split.*;
> import org.apache.hadoop.mapreduce.lib.input.*;
> import org.apache.hadoop.mapreduce.lib.output.*;
> import org.apache.hadoop.util.*;
> public class Sum extends Configured implements Tool{
> public static class MapClass extends
> Mapper<Text, Text, Text, IntWritable>{
> private static int i;
> private static int j;
> private static int a;
> private static int b;
> private String user;
> public void map(Text key,Text value,Context context)
> throws IOException, InterruptedException{
> String[] user_score =
> value.toString().split(" ");
> for(i=1;i<user_score.length-1;i+=2)
> for(j=i+2;j<user_score.length-1;j+=2){
> user = user_score[i]+" "+user_score[j];
> a = Integer.parseInt(user_score[i+1]);
> b = Integer.parseInt(user_score[j+1]);
> context.write(new Text(user),new
> IntWritable(a*b));
> }
> }
> }
> public static class Reduce extends
> Reducer<Text,IntWritable,Text,IntWritable>{
> public void reduce(Text key,Iterable<IntWritable> values,
> Context context) throws IOException, InterruptedException{
> int sum = 0;
>
> for(IntWritable val:values){
> sum += val.get();
> }
> context.write(key, new IntWritable(sum));
> }
> }
> public int run(String[] args) throws Exception{
> Configuration conf = getConf();
> Job job = new Job(conf,"Myjob");
> job.setJarByClass(Sum.class);
> Path in = new Path(args[0]);
> Path out = new Path(args[1]);
> FileInputFormat.setInputPaths(job,in);
> FileOutputFormat.setOutputPath(job,out);
> job.setMapperClass(MapClass.class);
> job.setCombinerClass(Reduce.class);
> job.setReducerClass(Reduce.class);
> job.setInputFormatClass(TextInputFormat.class);
> job.setOutputFormatClass(TextOutputFormat.class);
>
> job.setMapOutputKeyClass(Text.class);
> job.setMapOutputValueClass(IntWritable.class);
> job.setOutputKeyClass(Text.class);
> job.setOutputValueClass(IntWritable.class);
> System.exit(job.waitForCompletion(true)?0:1);
>
> return 0;
> }
> public static void main (String[] args) throws Exception{
> int res = ToolRunner.run(new Configuration(),new Sum(),args);
> System.exit(res);
> }
> }
>
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