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https://issues.apache.org/jira/browse/FLINK-1758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14484226#comment-14484226
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ASF GitHub Bot commented on FLINK-1758:
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Github user vasia commented on the pull request:
https://github.com/apache/flink/pull/576#issuecomment-90749788
Thanks for the PR @andralungu!
The idea for this issue is to (a) use a combinable reduce for the simple
(without vertex value) reduceOn* methods, because it will be more efficient and
(b) offer groupReduceOn* versions with Collectors to allow returning more than
one value per vertex.
I see you have implemented (b) here, but not (a).
To be more specific, the groupReduceOn* methods would be the ones with the
Collectors. Basically, you'll just have to rename what you have already
implemented. The reduceOn* methods will only return one value per vertex, like
they do currently, but internally use the reduce operator (instead of
reduceGroup).
For example, if you want to compute the sum of edge values, you can use the
`reduceOnEdges` method, same as you currently do. And if you want to compute
the Jaccard coefficient, you need to output multiple values per vertex and for
that you can use `groupReduceOnEdges`.
Please let me know if you have any questions! Thanks again :-)
> Extend Gelly's neighborhood methods
> -----------------------------------
>
> Key: FLINK-1758
> URL: https://issues.apache.org/jira/browse/FLINK-1758
> Project: Flink
> Issue Type: Improvement
> Components: Gelly
> Affects Versions: 0.9
> Reporter: Vasia Kalavri
> Assignee: Andra Lungu
>
> Currently, the neighborhood methods only allow returning a single value per
> vertex. In many cases, it is desirable to return several or no value per
> vertex. This is the case in clustering coefficient computation,
> vertex-centric jaccard, algorithms where a vertex computes a value per edge
> or when a vertex computes a value only for some of its neighbors.
> This issue proposes to
> - change the current reduceOnEdges/reduceOnNeighbors methods to use
> combinable reduce operations where possible
> - provide groupReduce-versions, which will use a Collector and allow
> returning none or more values per vertex.
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