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https://issues.apache.org/jira/browse/FLINK-4586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15576379#comment-15576379
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ASF GitHub Bot commented on FLINK-4586:
---------------------------------------
GitHub user greghogan opened a pull request:
https://github.com/apache/flink/pull/2639
[FLINK-4586] [core] Broken AverageAccumulator
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/greghogan/flink 4586_broken_averageaccumulator
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/2639.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #2639
----
commit 58d79b40ed837542e727c5f4f3a410ccb5f9ff24
Author: Greg Hogan <[email protected]>
Date: 2016-10-14T20:18:52Z
[FLINK-4586] [core] Broken AverageAccumulator
----
> NumberSequenceIterator and Accumulator threading issue
> ------------------------------------------------------
>
> Key: FLINK-4586
> URL: https://issues.apache.org/jira/browse/FLINK-4586
> Project: Flink
> Issue Type: Bug
> Components: DataSet API
> Affects Versions: 1.1.2
> Reporter: Johannes
> Assignee: Greg Hogan
> Priority: Minor
> Fix For: 1.2.0, 1.1.4
>
> Attachments: FLINK4586Test.scala
>
>
> There is a strange problem when using the NumberSequenceIterator in
> combination with an AverageAccumulator.
> It seems like the individual accumulators are reinitialized and overwrite
> parts of intermediate solutions.
> The following scala snippit exemplifies the problem.
> Instead of printing the correct average, the result should be {{50.5}} but is
> something completely different, like {{8.08}}, dependent on the number of
> cores used.
> If the parallelism is set to {{1}} the result is correct, which indicates a
> likely threading problem.
> The problem occurs using the java and scala API.
> {code}
> env
> .fromParallelCollection(new NumberSequenceIterator(1, 100))
> .map(new RichMapFunction[Long, Long] {
> var a : AverageAccumulator = _
> override def map(value: Long): Long = {
> a.add(value)
> value
> }
> override def open(parameters: Configuration): Unit = {
> a = new AverageAccumulator
> getRuntimeContext.addAccumulator("test", a)
> }
> })
> .reduce((a, b) => a + b)
> .print()
> val lastJobExecutionResult: JobExecutionResult = env.getLastJobExecutionResult
> println(lastJobExecutionResult.getAccumulatorResult("test"))
> {code}
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