[
https://issues.apache.org/jira/browse/MAHOUT-937?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Mat Kelcey updated MAHOUT-937:
------------------------------
Description:
The first pass of the collocations discovery job (as described by
CollocDriver.generateCollocations) uses the
org.apache.mahout.vectorizer.collocations.llr.GramKeyPartitioner partitioner.
This partitoner has an instance variable offset that is supposed to be set by a
call to setOffsets() but this call is never made (not sure why? is this method
expected to be called by the Hadoop framework itself?)
The offset not being set results in getPartition always returning 0 and so all
intermediate data is sent to the one reducer.
I couldn't quite understand what this partitioning was meant to be doing, but
simply hashing the Grams primary string representation (ie without the leading
'type' byte) does what is required...
{code}
public class GramKeyPartitioner extends Partitioner<GramKey, Gram> {
@Override
public int getPartition(GramKey key, Gram value, int numPartitions) {
// exclude first byte which is the key type
byte[] keyBytesWithoutTypeByte = new byte[key.getPrimaryLength()-1];
System.arraycopy(key.getBytes(), 1, keyBytesWithoutTypeByte, 0,
keyBytesWithoutTypeByte.length);
int hash = WritableComparator.hashBytes(keyBytesWithoutTypeByte,
keyBytesWithoutTypeByte.length);
return (hash & Integer.MAX_VALUE) % numPartitions;
}
}
{code}
was:
The first pass of the collocations discovery job (as described by
CollocDriver.generateCollocations) uses the
org.apache.mahout.vectorizer.collocations.llr.GramKeyPartitioner partitioner.
This partitoner has an instance variable offset that is supposed to be set by a
call to setOffsets() but this call is never made (not sure why? is this method
expected to be called by the Hadoop framework itself?)
The offset not being set results in getPartition always returning 0 and so all
intermediate data is sent to the one reducer.
I couldn't quite understand what this partitioning was meant to be doing, but
simply hashing the Grams primary string representation (ie without the leading
'type' byte) does what is required...
public class GramKeyPartitioner extends Partitioner<GramKey, Gram> {
@Override
public int getPartition(GramKey key, Gram value, int numPartitions) {
// exclude first byte which is the key type
byte[] keyBytesWithoutTypeByte = new byte[key.getPrimaryLength()-1];
System.arraycopy(key.getBytes(), 1, keyBytesWithoutTypeByte, 0,
keyBytesWithoutTypeByte.length);
int hash = WritableComparator.hashBytes(keyBytesWithoutTypeByte,
keyBytesWithoutTypeByte.length);
return (hash & Integer.MAX_VALUE) % numPartitions;
}
}
> Collocations Job Partitioner not being configured properly
> ----------------------------------------------------------
>
> Key: MAHOUT-937
> URL: https://issues.apache.org/jira/browse/MAHOUT-937
> Project: Mahout
> Issue Type: Bug
> Reporter: Mat Kelcey
> Priority: Minor
> Attachments: GramKeyPartitioner.java
>
>
> The first pass of the collocations discovery job (as described by
> CollocDriver.generateCollocations) uses the
> org.apache.mahout.vectorizer.collocations.llr.GramKeyPartitioner partitioner.
> This partitoner has an instance variable offset that is supposed to be set by
> a call to setOffsets() but this call is never made (not sure why? is this
> method expected to be called by the Hadoop framework itself?)
> The offset not being set results in getPartition always returning 0 and so
> all intermediate data is sent to the one reducer.
> I couldn't quite understand what this partitioning was meant to be doing, but
> simply hashing the Grams primary string representation (ie without the
> leading 'type' byte) does what is required...
> {code}
> public class GramKeyPartitioner extends Partitioner<GramKey, Gram> {
> @Override
> public int getPartition(GramKey key, Gram value, int numPartitions) {
> // exclude first byte which is the key type
> byte[] keyBytesWithoutTypeByte = new byte[key.getPrimaryLength()-1];
> System.arraycopy(key.getBytes(), 1, keyBytesWithoutTypeByte, 0,
> keyBytesWithoutTypeByte.length);
> int hash = WritableComparator.hashBytes(keyBytesWithoutTypeByte,
> keyBytesWithoutTypeByte.length);
> return (hash & Integer.MAX_VALUE) % numPartitions;
> }
>
> }
> {code}
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
