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From Stephan Ewen <se...@apache.org>
Subject Re: NullPointerException in DeltaIteration when no ForwardedFileds annotation
Date Mon, 27 Apr 2015 08:34:05 GMT
I think Fabian looked into this a while back...

@Fabian, do you have any insights what causes this?


On Sat, Apr 25, 2015 at 7:46 PM, Vasiliki Kalavri <vasilikikalavri@gmail.com
> wrote:

> Hi,
>
> I actually ran into this problem again with a different algorithm :/
> Same exception and it looks like getMatchFor() in CompactingHashTable
> returns a null record.
> Not sure why or why the annotation prevents this from happening. Any
> insight is highly welcome :-)
>
> Shall I open an issue so that we don't forget about this?
>
> -Vasia.
>
>
> On 4 April 2015 at 14:44, Vasiliki Kalavri <vasilikikalavri@gmail.com>
> wrote:
>
> > Hi Fabian,
> >
> > thanks for looking into this.
> > Let me know if there's anything I can do to help!
> >
> > Cheers,
> > V.
> >
> > On 3 April 2015 at 22:31, Fabian Hueske <fhueske@gmail.com> wrote:
> >
> >> Thanks for the nice setup!
> >> I could easily reproduce the exception you are facing.
> >> But that's the only good news so far :-(
> >>
> >> I checked the plans and both are valid and should compute the correct
> >> result for the program.
> >> The split-of solution set delta is required because the it needs to be
> >> repartitioned (without the annotation, the optimizer does not know that
> it
> >> is in fact already correctly partitioned). One thing that made me a bit
> >> suspicious is that the solution set delta partitioning is marked with a
> >> Pipeline-Breaker. The pipeline breaker shouldn't make a semantic
> >> difference, but I am not sure if it is really required and also that
> part
> >> of the codebase was recently worked on.
> >>
> >> So, a closer look and more debugging is necessary to figure out what not
> >> working correctly here...
> >>
> >>
> >> 2015-04-03 14:14 GMT+02:00 Vasiliki Kalavri <vasilikikalavri@gmail.com
> >:
> >>
> >> > Hi Fabian,
> >> >
> >> > I am using the dblp co-authorship dataset from SNAP:
> >> > http://snap.stanford.edu/data/com-DBLP.html
> >> > I also pushed my slightly modified version of ConnectedComponents,
> here:
> >> > https://github.com/vasia/flink/tree/cc-test. It basically generates
> the
> >> > vertex dataset from the edges, so that you don't need to create it
> >> > separately.
> >> > The annotation that creates the error is in line #172.
> >> >
> >> > Thanks a lot :))
> >> >
> >> > -Vasia.
> >> >
> >> >
> >> > On 3 April 2015 at 13:09, Fabian Hueske <fhueske@gmail.com> wrote:
> >> >
> >> > > That looks pretty much like a bug.
> >> > >
> >> > > As you said, fwd fields annotations are optional and may improve the
> >> > > performance of a program, but never change its semantics (if set
> >> > > correctly).
> >> > >
> >> > > I'll have a look at it later.
> >> > > Would be great if you could provide some data to reproduce the bug.
> >> > > On Apr 3, 2015 12:48 PM, "Vasiliki Kalavri" <
> >> vasilikikalavri@gmail.com>
> >> > > wrote:
> >> > >
> >> > > > Hello to my squirrels,
> >> > > >
> >> > > > I've been getting a NullPointerException for a DeltaIteration
> >> program
> >> > I'm
> >> > > > trying to implement and I could really use your help :-)
> >> > > > It seems that some of the input Tuples of the Join operator that
> I'm
> >> > > using
> >> > > > to create the next workset / solution set delta are null.
> >> > > > It also seems that adding ForwardedFields annotations solves
the
> >> issue.
> >> > > >
> >> > > > I managed to reproduce the behavior using the ConnectedComponents
> >> > > example,
> >> > > > by removing the "@ForwardedFieldsFirst("*")" annotation from
> >> > > > the ComponentIdFilter join.
> >> > > > The exception message is the following:
> >> > > >
> >> > > > Caused by: java.lang.NullPointerException
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.examples.java.graph.ConnectedComponents$ComponentIdFilter.join(ConnectedComponents.java:186)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.examples.java.graph.ConnectedComponents$ComponentIdFilter.join(ConnectedComponents.java:1)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.runtime.operators.JoinWithSolutionSetSecondDriver.run(JoinWithSolutionSetSecondDriver.java:198)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.runtime.operators.RegularPactTask.run(RegularPactTask.java:496)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.runtime.iterative.task.AbstractIterativePactTask.run(AbstractIterativePactTask.java:139)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.runtime.iterative.task.IterationIntermediatePactTask.run(IterationIntermediatePactTask.java:92)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.runtime.operators.RegularPactTask.invoke(RegularPactTask.java:362)
> >> > > > at
> >> > > >
> >> > > >
> >> > >
> >> >
> >>
> org.apache.flink.runtime.execution.RuntimeEnvironment.run(RuntimeEnvironment.java:217)
> >> > > > at java.lang.Thread.run(Thread.java:745)
> >> > > >
> >> > > > I get this error locally with any sufficiently big dataset (~10000
> >> > > nodes).
> >> > > > When the annotation is in place, it works without problem.
> >> > > > I also generated the optimizer plans for the two cases:
> >> > > > - with annotation (working):
> >> > > > https://gist.github.com/vasia/4f4dc6b0cc6c72b5b64b
> >> > > > - without annotation (failing):
> >> > > > https://gist.github.com/vasia/086faa45b980bf7f4c09
> >> > > >
> >> > > > After visualizing the plans, the main difference I see is that
in
> >> the
> >> > > > working case, the next workset node and the solution set delta
> nodes
> >> > are
> >> > > > merged, while in the failing case they are separate.
> >> > > >
> >> > > > Shouldn't this work with and without annotation (but be more
> >> efficient
> >> > > with
> >> > > > the annotation in place)? Or am I missing something here?
> >> > > >
> >> > > > Thanks in advance for any help :))
> >> > > >
> >> > > > Cheers,
> >> > > > - Vasia.
> >> > > >
> >> > >
> >> >
> >>
> >
> >
>

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