[jira] [Created] (MAHOUT-2096) next() Called On Possible Empty iterator()

["Shangru Li (Jira)" <ji...@apache.org>]

Shangru Li created MAHOUT-2096:
----------------------------------

             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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