Hi,
I have been unsuccessfully trying to set the map output value class
different to the one reduce outputs (in 0.16.0). AFAIK the following should
do the trick:
conf.setMapOutputValueClass(FooWritable.class)
conf.setOutputValueClass(BarWritable.class)
However I kept getting exceptions saying BarWritable is not FooWritable.
Both classes implements WritableComparable.
java.io.IOException: wrong value class: test.BarWritable is not class
test.FooWritable
at org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java
:952)
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer$2.collect(
MapTask.java:489)
at edu.umd.cs.hadoopImage.HadoopImg$InpaintReduceClass.reduce(
HadoopImg.java:122)
at edu.umd.cs.hadoopImage.HadoopImg$InpaintReduceClass.reduce(
HadoopImg.java:1)
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.combineAndSpill(
MapTask.java:522)
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpillToDisk(
MapTask.java:493)
at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java
:713)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:209)
at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java
:2071)
Suggestions? Thanks.
- Chang
--
---------------
Überstehen ist alles.
Chang Hu
Ph.D. student
Computer Science Department
University of Maryland
