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From Eli Reisman <>
Subject Re: InputFormat for the example SimpleMasterComputeVertex
Date Fri, 22 Feb 2013 00:21:48 GMT
That sounds great to me, maybe just a mention in the wiki that the two
functionalities are tied together will help the idea click for people.
Either way this will be a big help I think.

On Thu, Feb 21, 2013 at 3:24 PM, Maja Kabiljo <> wrote:

>  Eli, that's an interesting idea, we could have some class which user
> extends and which is there only for aggregator registration. Sometimes we
> want to register some aggregators later on during the computation, so we
> need to keep allowing registration from masterCompute too.
>  But I think for users the biggest problem is to realize that they have
> to extend and set MasterCompute/this new class in order to use aggregators.
> Currently, if user tries to aggregate a value to unregistered aggregator he
> will get an exception, but if he tries to get the value of unregistered
> aggregator he will just get null. So maybe adding a warning message in that
> case, together with a wiki page, might be enough? What do you think?
>   From: Eli Reisman <>
> Reply-To: "" <>
> Date: Thursday, February 21, 2013 10:25 AM
> To: "" <>
> Subject: Re: InputFormat for the example SimpleMasterComputeVertex
>  Thanks for the explanation, that makes sense. I would love to see a wiki
> page at some point, you have so much knowledge of this piece of Giraph from
> all your dev work on it and have also the additional bonus of experience
> running big cluster jobs using these features so you have a lot of insight
> to share.
>  Would there be any point to a future JIRA to break out the aggregator
> registration from the master compute stuff, at least from the user's view?
> Or is it not that confusing once you've used them a bit?
> On Thu, Feb 14, 2013 at 4:52 PM, Maja Kabiljo <> wrote:
>>  Progressable exception can be caused by many different reasons (it's
>> totally unrelated to aggregators), and when looking at which exception it's
>> caused by users should get better sense about what's going on.
>> What you are suggesting about providing default master compute is not
>> doable, since the part which needs to be done there is aggregator
>> registration. We can't know what kind of aggregators (names and types) an
>> application needs.
>> I remember I was talking about writing a short tutorial for aggregators
>> long time ago, sorry for not doing that, will try to get to it soon.
>>   From: Eli Reisman <>
>> Reply-To: "" <>
>> Date: Thursday, February 14, 2013 2:23 PM
>> To: "" <>
>> Subject: Re: InputFormat for the example SimpleMasterComputeVertex
>>   Other folks on the list are also having this problem with the
>> progressable utile exception & job failures. I don't know much about master
>> compute usage but if it is needed to make the aggregators work, maybe we
>> should have a default dummy class that just handles aggregators if no other
>> master compute is specified? Or a wiki page? The progressable error message
>> does not lead us to this conclusion directly.
>> On Wed, Feb 13, 2013 at 3:04 AM, Maria Stylianou <>wrote:
>>> Hey,
>>>  I am trying to run the example SimpleMasterComputeVertex, but no
>>> matter which Input Format and graph I give, it doesn't work. Each worker
>>> gives the error:
>>> Caused by: java.lang.*NullPointerException*
>>> 	at org.apache.giraph.examples.*SimpleMasterComputeVertex.compute*(*42*)
>>> This line 42 is the first line of the compute()
>>> public void compute(Iterable<DoubleWritable> messages){
>>>  So I guess, the initialization is not done correctly, because the
>>> input file does not have the correct format.
>>>  Any help would be appreciated,
>>> Thanks!
>>>  Maria
>>> --
>>> Maria Stylianou
>>> Intern at Telefonica, Barcelona, Spain
>>> Master Student of European Master in Distributed Computing<>
>>> Universitat Polit├Ęcnica de Catalunya - BarcelonaTech, Barcelona, Spain
>>>  KTH Royal Institute of Technology, Stockholm, Sweden

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