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From Stephan Ewen <se...@apache.org>
Subject Re: Spargel pagerank with sinks
Date Thu, 18 Sep 2014 15:29:07 GMT
Hi!

With "sinks" in the graph, you mean vertices with no out-links?

There might be a simple trick, by adding to each vertex an edge-to-self
(put an entry in the diagonal of the adjacency matrix).

I have not thought through the implications 100%.
@ssc Can you elaborate on this?


What would always work is that you gather statistics about how much
probability is accumulated in the sinks and redistribute it across the
other nodes.

The iteration aggregators allow you to do this. They can sum up the
probability in the message sender function (when there is no outgoing edge),
and re-add it to the non-sink nodes (by accessing the aggregate from the
previous iteration).

Have a look at the function "registerAggregator()" on the
"VertexCentricIteration", and the Functions "getIterationAggregator()" and
"getPreviousIterationAggregate()" on the VertexUpdateFunction and the
MessagingFunction.


Stephan

On Thu, Sep 18, 2014 at 5:01 PM, Attila BernĂ¡th <bernath.athos@gmail.com>
wrote:

> Dear All,
>
> I wonder how to write the pagerank program in the spargel API if there
> might be sinks in the graph.
>
> What is the nicest way to solve this?
>
> Thank you for your answer.
>
> Attila
>

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