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https://issues.apache.org/jira/browse/SPARK-13902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15257481#comment-15257481
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Takuya Ueshin commented on SPARK-13902:
---------------------------------------
I'm sorry, I made a mistake.
I should have written the number in the diagram, but I wrote the actual shuffle
id from DAGScheduler we can get when we run the test.
I'll update it.
So the rest of your questions are right.
> Make DAGScheduler.getAncestorShuffleDependencies() return in topological
> order to ensure building ancestor stages first.
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-13902
> URL: https://issues.apache.org/jira/browse/SPARK-13902
> Project: Spark
> Issue Type: Bug
> Components: Scheduler
> Reporter: Takuya Ueshin
>
> {{DAGScheduler}} sometimes generate incorrect stage graph.
> Some stages are generated for the same shuffleId twice or more and they are
> referenced by the child stages because the building order of the graph is not
> correct.
> Here, we submit an RDD\[F\] having a linage of RDDs as follows (please see
> this in {{monospaced}} font):
> {noformat}
> <--------------------
> / \
> [A] <--(1)-- [B] <--(2)-- [C] <--(3)-- [D] <--(4)-- [E] <--(5)-- [F]
> \ /
> <--------------------
> {noformat}
> {{DAGScheduler}} generates the following stages and their parents for each
> shuffle id:
> | shuffle id | stage | parents |
> | 0 | ShuffleMapStage 2 | List() |
> | 1 | ShuffleMapStage 1 | List(ShuffleMapStage 0) |
> | 2 | ShuffleMapStage 3 | List(ShuffleMapStage 1) |
> | 3 | ShuffleMapStage 4 | List(ShuffleMapStage 2, ShuffleMapStage 3) |
> | 4 | ShuffleMapStage 5 | List(ShuffleMapStage 1, ShuffleMapStage 4) |
> | \- | ResultStage 6 | List(ShuffleMapStage 5) |
> The stage for shuffle id {{0}} should be {{ShuffleMapStage 0}}, but the stage
> for shuffle id {{0}} is generated twice as {{ShuffleMapStage 2}} and
> {{ShuffleMapStage 0}} is overwritten by {{ShuffleMapStage 2}}, and the stage
> {{ShuffleMap Stage1}} keeps referring the _old_ stage {{ShuffleMapStage 0}}.
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