Shangru Li created MAHOUT-2096:
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Summary: next() Called On Possible Empty iterator()
Key: MAHOUT-2096
URL: https://issues.apache.org/jira/browse/MAHOUT-2096
Project: Mahout
Issue Type: Bug
Components: Algorithms
Reporter: Shangru Li
Consider this function:
{quote}
protected void reduce ( VarIntWritable index, Iterable<VarLongWritable> ids,
Context
ctx) throws IOException, InterruptedException {
ctx.write(index, ids.iterator().next());
}
{quote}
The line `_ctx.write(index, ids.iterator().next());_` does not check for empty
iterator when calling the next() function, which could result in an exception.
Function can be found on the GitHub repository
[here|[https://github.com/apache/mahout/blob/754068bc3ac62bcf4b9b656cd4a6f413b29b18df/community/mahout-mr/mr/src/main/java/org/apache/mahout/cf/taste/hadoop/als/ParallelALSFactorizationJob.java#L395].]
Line 395, in file
_/src/main/java/org/apache/mahout/cf/taste/hadoop/als/ParallelALSFactorizationJob.java_
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