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Date: Tue, 29 May 2012 12:13:28 +0100
From: Paolo Castagna <castagna.lists@googlemail.com>
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Subject: Re: SimplePageRankVertex implementation, dangling nodes and sending
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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.

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