port to Chapel

[jeffhammond]

@bradcray Please let me know how we can help here.

[bradcray]

One of our team members is actively working on porting some PRKs (along with a few other non-PRK tasks) and understanding performance gaps. Most of his work has been on stencil so far (shared-memory only, so far, I think?) though I believe he's also started in on transpose this week. So far I think things have been clear enough on the PRK side of things and we won't hesitate to contact you, Rob, and Ulf when questions come up.

[jeffhammond]

In case anyone from the internet comes along and finds this issue, please see https://github.com/chapel-lang/chapel/tree/master/test/studies/prk for now.

[ian-bertolacci]

Someone should bug the authors of this paper: Comparative Performance and Optimization of Chapel in Modern Manycore Architectures

They should have a few PRKs, but I dont know where they are.

[bradcray]

@ian-bertolacci : We've been (slowly) working with Engin to get copies of his PRKs, review them, and add them to the test/studies directory Jeff mentions above.

[jeffhammond]

https://github.com/e-kayrakli/chapel_prk are the droids you are looking for. @e-kayrakli may have additional comments.

[e-kayrakli]

My repo is not as reliable as the ones that are in the Chapel repo -- https://github.com/chapel-lang/chapel/tree/master/test/studies/prk . Even the versions that got merged to the Chapel master was slightly different then the ones I have there (and they have seen couple revisions later). And I still make changes to my repo willy-nilly. Frankly, I forgot I left it public :)

[jeffhammond]

@e-kayrakli @bradcray It would be great if someone could put together a PR of p2p, stencil, and transpose, at least. I will likely do an in-depth study of the "big 3" PRKs for shared-memory in the near future, and I'd like to be able to include Chapel here.

Every time I look at the various Chapel PRK implementations, I can never figure out which ones are the latest and best.

[e-kayrakli]

I think p2p would be the one that requires the most work among those. I'd say the other two are in a much better shape, at least for shared memory studies.

FWIW, a to-do list for PRKs in Chapel: chapel-lang/chapel#6162

[jeffhammond]

You might look at my recent p2p ports eg in the Cxx11 folder. If Chapel supports task dependencies similar to OpenMP, then it’s really easy to write a shared-memory implementation that performs well. There’s also a data-parallel version that loops over anti-diagonals. Neither of these is suitable for distributed memory though.