Hi Greg and Vasia, thanks for starting this discussion. I think it is a good idea to update the Gelly roadmap. As Vasia said, many items on the list have been implemented and other have been more or less dropped. Also new persons who want to improve Gelly have joint the community while others have become idle. So from my point of view it makes perfect sense to gather the input of the community and update the Gelly roadmap.
Regarding the specific changes of FLINK-3772, I am usually always in favor of performance improvements. How much would the suggested functionality for degree computation overlaps with the current methods? Could the current methods be replaced by the more efficient implementations or would there be two methods which look very similar and behave almost the same? Best, Fabian 2016-04-22 11:00 GMT+02:00 Vasiliki Kalavri <vasilikikala...@gmail.com>: > Hi all, > > I asked Greg to start a discussion here about FLINK-3771 and FLINK-3772, to > make sure we're all on the same page about future Gelly development. > > About a year ago we created the Gelly roadmap [1]. Many of these items have > been implemented and others were researched and either developed externally > or dropped. Graph translators and degree annotations were not in the > roadmap, but I personally think that they are both helpful features and I'm > in favor of adding them to Gelly. > > That said, I find this a perfect timing for revisiting and updating our > Gelly development plans. We should update the roadmap so that it reflects > current state and future plans. This way, the community can have a clear > picture of what we are working on and what are upcoming features. This is > also very important for new contributors. They can always refer to the > roadmap to see what the community is interested in and we can avoid having > people spending their time on obsolete or dropped features. We should also > go through existing JIRAs and clean them up. Several are assigned to people > who have been inactive or might need help. > > In the following days I will go through the roadmap and then start a new > thread where we can discuss features and agree on future plans. In the > meantime, it would be great if you give us your view on FLINK-3771 and > FLINK-3772. > > Cheers, > -Vasia. > > [1]: https://cwiki.apache.org/confluence/display/FLINK/Flink+Gelly > > On 21 April 2016 at 18:52, Greg Hogan <c...@greghogan.com> wrote: > > > Vasia and I are looking for additional feedback on FLINK-3772. This > ticket > > [0] and PR [1] provides a set of graph algorithms which compute and store > > the degree for vertices and edges. > > > > Degree annotation is a basic component of many algorithms. For example, > > PageRank requires the vertex out-degree to evenly divide the vertex score > > among neighbors. The triangle enumeration algorithm in Gelly requires > both > > source and target degree for each edge as an optimization. The Jaccard > and > > Adamic-Adar similarities require the target degree for each edge. > > > > As discussed in the ticket, Graph has methods for outDegrees, inDegrees, > > and getDegrees. These are simple but difficult or impossible to use > > efficiently. > > > > Stepping back, I believe algorithms should be composable and reused where > > possible, not only to improve Flink but also to support users. > Implementing > > algorithms as classes rather than Graph methods enables customization and > > optimization such as used here. > > > > One such optimization is CachingGraphAlgorithm which implicitly reuses > > DataSets. There is overlap between algorithms. From this ticket, > annotating > > edges with source and target degree on an undirected graph can reuse > vertex > > degree. Local clustering coefficient requires a triangle listing and > global > > clustering coefficient requires a triangle count, there is no need to > > generate the list three times. > > > > Further optimizations include the use of mutable types, reusing sort > order, > > avoidance of coGroup, configurable parallelism, and not unnecessarily > > materializing DataSets. I see all this as the expectation for inclusion > in > > Flink. > > > > Greg > > > > [0] https://issues.apache.org/jira/browse/FLINK-3772 > > [1] https://github.com/apache/flink/pull/1901/files > > >
