spectralkmeans utility fails when input filename begins with leading underscore
-------------------------------------------------------------------------------
Key: MAHOUT-978
URL: https://issues.apache.org/jira/browse/MAHOUT-978
Project: Mahout
Issue Type: Bug
Components: Clustering
Affects Versions: 0.6
Environment: Tested on a real Linux-based cluster running Hadoop
0.20.2-cdh3u2 and the 0.6 release; also OSX pseudo cluster running Hadoop
0.20.203.0 running 16 Feb trunk build.
Reporter: Dan Brickley
Priority: Minor
The commandline 'bin/mahout spectralkmeans' utility fails with
NoSuchElementException after "Loading vector from:
spectral/output/results2/calculations/diagonal/part-r-00000" when input data
in hdfs has filename beginning with a leading underscore.
This was partially reported in comments for MAHOUT-524 but I believe identified
now as a distinct issue (thanks to Shannon for help diagnosing). I have not
investigated if there is an equivalent problem for API-based use of this piece
of Mahout.
Steps to reproduce:
1. put affinity file into hdfs, following
https://cwiki.apache.org/MAHOUT/spectral-clustering.html - note that node IDs
count from zero etc. Name your file with a leading underscore. For example, try
http://danbri.org/2012/spectral/dbpedia/_topic_skm.csv and store it in
spectral/input/_topic_skm.csv
(I'll leave that example input file in place unchanged for others to try. It is
built from dbpedia data, encoding associations from Wikipedia pages to
categories. Whether it is a good use of spectral clustering I'm not sure, but
I'd at least hope the job would run to completion.)
2. Run 'mahout spectralkmeans -k 20 -d 4192499 -x 7 -i spectral/input/ -o
spectral/output/results1'
3. Wait for it to fail just after printing "Loading vector from:
spectral/output/results1/calculations/diagonal/part-r-00000", with
java.util.NoSuchElementException at
com.google.common.collect.AbstractIterator.next(AbstractIterator.java:152).
4. Rename the file in hdfs to eliminate the leading underscore. Re-run the
command (give a different results dir or cleanup from the first run, to avoid
mixing the tests). This attempt should succeed and you'll see it proceed deeper
into the job, i.e. something like
12/02/19 14:38:32 INFO common.VectorCache: Loading vector from:
spectral/output/results2/calculations/diagonal/part-r-00000
12/02/19 14:38:41 WARN mapred.JobClient: Use GenericOptionsParser for parsing
the arguments. Applications should implement Tool for the same.
12/02/19 14:38:43 INFO input.FileInputFormat: Total input paths to process : 1
12/02/19 14:38:44 INFO mapred.JobClient: Running job: job_201202191410_0005
12/02/19 14:38:45 INFO mapred.JobClient: map 0% reduce 0%
12/02/19 14:39:31 INFO mapred.JobClient: map 1% reduce 0%
(5. You might get a memory-based failure some time later; that is a separate
problem.)
I'll attach a more detailed transcript. I've made no attempt to diagnose
internals yet, but did make some other tests and can confirm that it does not
seem to matter whether the commandline invocation names the file explicitly, or
by directory name only. Also trailing slash does not seem to be an issue.
Finally, a related 'gotcha': make sure the results directory is not inside the
input directory when testing.
--
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
