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From Vasiliki Kalavri <vasilikikala...@gmail.com>
Subject Re: [DISCUSS] Gelly planning for release 1.3 and roadmap
Date Wed, 01 Mar 2017 06:57:42 GMT
Hi Xingcan,

thank you for your input!

On 27 February 2017 at 14:03, Xingcan Cui <xingcanc@gmail.com> wrote:

> Hi Vasia and Greg,
>
> thanks for the discussion. I'd like to share my thoughts.
>
> 1) I don't think it's necessary to extend the algorithm list intentionally.
> It's just like a textbook that can not cover all the existing algorithms
> (even if we can). Just representative and commonly used ones will be
> enough. After all, Gelly is mainly designed for providing a framework
> rather than an algorithm library. Besides, it seems that Gelly's API is not
> stable now and thus a huge work of refactoring or even rewriting will rise
> once the API changes.
>

​In fact, Gelly's main APIs haven't changed much throughout the last 3
releases.
Maybe it's time we explicitly mark stable API​s for 1.3.



>
> 2) Unlike other "pure" graph computing framework (e.g. giraph), Gelly is
> built on top of Flink, which means that it can only use operations that
> provided by it. In my own opinion, Flink's batch processing is not so
> outstanding as it's stream. As Grey said, one problem lies on intermediate
> results caching. Though it's not clear for me (I'm still a ignorant new
> comer...) why this feature has not been implemented for such a long time,
> there must be some reasons. What I see is that, to some extent, it's
> already obstructed Gelly's development. From this point of view,
> self-blessing is better than blessing from others and I'm sure some MLers
> may be more anxious than us :) So, I guess "within Gelly" just means a
> Gelly-driven development?
>
> In a nutshell, I will encourage more concentrations on Gelly's API (or even
> related Flink's API if necessary), rather than high-level things (e.g.
> algorithms, performance) on top of it. What if we can change both the
> edges' values and vertices' values during an iteration one day? :)
>

​Changing both edge and vertex values during an iteration has also been
brought up before.
This one could be implemented by providing an alternative representation of
the graph (e.g. adjacency list)
and would (hopefully) leave existing iteration APIs unchanged. I'm onboard
with adding this to the roadmap​.

Best,
-Vasia.


>
> Best,
> Xingcan
>
>
> On Sat, Feb 25, 2017 at 2:43 AM, Vasiliki Kalavri <
> vasilikikalavri@gmail.com
> > wrote:
>
> > Hi Greg,
> >
> > On 24 February 2017 at 18:09, Greg Hogan <code@greghogan.com> wrote:
> >
> > > Thanks, Vasia, for starting the discussion.
> > >
> > > I was expecting more changes from the recent discussion on
> restructuring
> > > the project, in particular regarding the libraries. Gelly has always
> > > collected algorithms and I have personally taken an algorithms-first
> > > approach for contributions. Is that manageable and maintainable? I'd
> > prefer
> > > to see no limit to good contributions, and if necessary split the
> > codebase
> > > or the project.
> > >
> >
> > ​I don't think there should be a limit either. I do think though that
> > development should be community-driven, i.e. not making contributions
> just
> > for the sake of it, but evaluating their benefit first.
> > The library already has a quite long list of algorithms. Shall we keep on
> > extending it? And if yes, how do we choose which algorithms to add? Do we
> > accept any algorithm even if it hasn't been asked by anyone? So far,
> we've
> > added algorithms that we thought were useful and common. But continuing
> to
> > extend the library like this doesn't seem maintainable to me, because we
> > might end up with a lot of code to maintain that nobody uses. On the
> other
> > hand, adding more algorithms might attract more users, so I see a
> trade-off
> > there.
> >
> >
> > >
> > > If so, then a secondary goal is to make the algorithms user-accessible
> > and
> > > easier to review (especially at scale!). FLINK-4949 rewrites
> > > flink-gelly-examples with modular inputs and algorithms, allows users
> to
> > > run all existing algorithms, and makes it trivial to create a driver
> for
> > > new algorithms (and when comparing different implementations).
> > >
> >
> > ​I'm +1 for anything that makes using existing functionality easier.
> > FLINK-4949 sounds like a great addition. Could you maybe extend the JIRA
> > and/or PR description a bit? I understand the rationale but it would be
> > nice to have a high-level description of the changes and the new
> > functionality that the PR adds or the interfaces it modifies. Otherwise,
> it
> > will be difficult to review a PR with +5k line changes :)
> >
> >
> >
> > >
> > > Regarding BipartiteGraphs, without algorithms or ideas for algorithms
> > it's
> > > not possible to review the structure of the open pull requests.
> > >
> >
> >
> > ​I'm not sure I understand this point. There was a design document and an
> > extensive discussion on this issue. Do you think we should revisit? Some
> > common algorithms for bipartitite graphs that I am aware of is SALSA for
> > recommendations and relevance search for anomaly detection.
> >
> >
> >
> > >
> > > +1 to evaluating performance and promoting Flink!
> > >
> > > Gelly has two shepherds whereas CEP and ML share one committer. New
> > > algorithms in Gelly require new features in the Batch API (Gelly may
> also
> > > start doing streaming, we're cool kids, too)
> >
> >
> > ​^^​
> >
> >
> > > so we need to find a process
> > > for snuffing ideas early and for the right balance in dependence on
> core
> > > committers' time. For example, reworking the iteration scheduler to
> allow
> > > for intermediate outputs and nested iterations. Can this feature be
> > > developed and reviewed within Gelly?
> >
> > Does it need the blessing of a Stephan
> > > or Fabian? I'd like to see contributors and committers less dependent
> on
> > > the core team and more autonomous.
> > >
> >
> > ​What do you mean
> > ​developed and reviewed ​
> > "within Gelly"?
> > ​This feature would require changes in the batch iterations code and will
> > probably need to be proposed and reviewed as a FLIP, so it would need the
> > blessing of the community :)
> >
> > Having someone who is more familiar with this part of the code help is of
> > course favorable, but I don't think it's absolutely necessary.
> >
> > ​-V.​
> >
> >
> > > Greg
> > >
> > > On Fri, Feb 24, 2017 at 10:39 AM, Vasiliki Kalavri <
> > > vasilikikalavri@gmail.com> wrote:
> > >
> > > > Hello squirrels,
> > > >
> > > > this is a discussion thread to organize the Gelly component
> development
> > > for
> > > > release 1.3 and discuss longer-term plans for the library.
> > > >
> > > > I am hoping that with time-based releases, we can distribute the load
> > for
> > > > PR reviewing and make better use of our time, and also point
> > contributors
> > > > to "useful" tickets when they offer to help.
> > > >
> > > > I'm expecting the outcome of this discussion to be:
> > > >
> > > > (1) a set of open PRs to review and try merging for 1.3
> > > > (2) a set of open JIRAs to work-on before feature freeze
> > > > (3) a set of JIRAs and PRs to reorganize/close
> > > > (4) ideas on possible FLIPs
> > > >
> > > > Here's my initial take on things, i.e. features *I* see as important
> in
> > > the
> > > > short-term. Feel free to add/remove/discuss:
> > > >
> > > > Release 1.3
> > > > ==========
> > > > - Bipartite graph support. Initial support has been added, but there
> > > > are unreviewed
> > > > PRs
> > > > <https://github.com/apache/flink/pulls?utf8=%E2%9C%93&q=
> > > > is%3Apr%20is%3Aopen%20bipartite%20>
> > > > and there is no Scala API yet. It would be nice to organize this
> > feature,
> > > > decide what functionality we need and what functionality is already
> > > covered
> > > > by the Graph type and have proper bipartite support for 1.3.
> > > > - Driver improvements, i.e. #3294
> > > > <https://github.com/apache/flink/pull/3294>
> > > > - Algorithm improvements, #2733 <https://github.com/apache/fli
> > > nk/pull/2733
> > > > >
> > > > - Affinity Propagation algorithm. This one has been developed using a
> > > bulk
> > > > iteration plan and needs a review. The PR is #2885
> > > > <https://github.com/apache/flink/pull/2885>.
> > > > - Object reuse issues, FLINK-5890, FLINK-5891
> > > > - Vertex-centric iteration improvement, i.e. FLINK-5127
> > > >
> > > >
> > > > Roadmap
> > > > ========
> > > > Regarding longer-term plans, I see the following issues as still
> being
> > > > relevant from the existing roadmap [1]:
> > > > - Extending the iteration functionality to support algorithms, more
> > > complex
> > > > than value-propagation, e.g. with nested loops
> > > > - Partitioning methods
> > > > - Partition-centric iterations
> > > > - Performance evaluation
> > > >
> > > > These two lists are by no means complete or final and the goal of
> this
> > > > thread is to see what the community is interested in, whether these
> > > > features / additions make sense to be worked on, or what features are
> > > > missing.
> > > > So, please provide your feedback!
> > > >
> > > > Cheers,
> > > > -V.
> > > >
> > > > [1]: https://cwiki.apache.org/confluence/display/FLINK/Flink+Gelly
> > > >
> > >
> >
>

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