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Date: Tue, 29 May 2012 13:48:46 +0200
From: Sebastian Schelter <ssc@apache.org>
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Subject: Re: SimplePageRankVertex implementation, dangling nodes and sending
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On 29.05.2012 13:13, Paolo Castagna wrote:
> Hi Sebastian
> 
> Sebastian Schelter wrote:
>> Why do you only recompute the pageRank in each second superstep? Can we
>> not use the aggregated value of the dangling nodes from the last superstep?
> 
> I removed the computing of PageRank values every each second superstep.
> However, I needed to use a couple of aggregators for the dangling nodes
> contribution instead of just one: "dangling-current" and "dangling-previous".
> 
> Each superstep, I need to reset the dangling-current aggregator, at the
> same time, I need to know the value of the aggregator at a previous
> superstep.

You can save the value from the previous step in a static variable in
the WorkerContext before resetting the aggregator.

> 
> I hope it makes sense, let me know if you have a better idea.
> 
>> Overall I think we're on a good way to a robust, real-world PageRank
>> implementation, I managed to implement the convergence check with an
>> aggregator, will post an updated patch soon.
> 
> I think I've just done it, have a look [1] and let me know if you would have
> done it differently.
> 
> Paolo
> 
>  [1]
> https://github.com/castagna/jena-grande/blob/11f07dd897562f7a4bf8d6e4845128d7f2cdd2ff/src/main/java/org/apache/jena/grande/giraph/pagerank/PageRankVertex.java#L90
> 
>