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From "Jan van der Lugt (JIRA)" <>
Subject [jira] [Commented] (GIRAPH-243) EdgeListVertex performance is sub-optimal
Date Sun, 08 Jul 2012 03:00:36 GMT


Jan van der Lugt commented on GIRAPH-243:

Seems to me like a good proposal. Might be good to do some benchmarking in order to get a
sense of how much speed we gain by such a modification. What would be the best way to do this?
The benchmark classes don't use edge values, as far as I know, only the SSSP example uses
> EdgeListVertex performance is sub-optimal
> -----------------------------------------
>                 Key: GIRAPH-243
>                 URL:
>             Project: Giraph
>          Issue Type: Improvement
>          Components: graph
>            Reporter: Alessandro Presta
>            Assignee: Alessandro Presta
> Iterating over outgoing edges (both vertex id and value) in an EdgeListVertex is O(n
log n): you have to iterate over getOutEdgesIterator and call getEdgeValue (which is logarithmic)
at each iteration.
> If we store the edge list as a list of Edge<I, E> (instead of the current two lists),
iteration becomes linear time (which I think is what most people expect from an adjacency-list
> Furthermore, I think we can avoid sorting the list by ID: addEdge and removeEdge are
currently linear-time because we are using an ArrayList, so the binary search doesn't help
much. If we don't sort, at least addEdge becomes amortized constant-time.
> This improvement would require an API change: getOutEdgesIterator should iterate over
Edge<I, E> as opposed to just I.
> What I propose is to have both iterators (the current one could be called getNeighborsIterator),
with a default implementation of the neighbors iterator in terms of the edges iterator, and
optimizations left to implementors (e.g. IntIntNullIntVertex).

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