Cartesian Biweekly 2020 09 01

Action Points

[ ] @Tobias W, @Oli F Present outcome of HPC4WC student projects (once they are graded)
[ ] @Enrique G. P will report on how the Daint testing for GPU backends is working
[ ] @Eddie D Will work on multistage issue with gt4py devs
[ ] @Enrique G. P, @Johann D Will review regions toolchain implementation
[ ] @Johann D will create a doodle poll to setup the next gtscript workshop (after Sept. 20)
[ ] @Johann D will add “Change computation to vertical" to gtscript workshop
[ ] @Enrique G. P will add language to the parallel model about conditions
[ ] @Hannes will push on finishing parallel model conditional language given example from @Tobias W (disallow pattern only for point-based if?)
[ ] @Enrique G. P will ask Mauro about documentation and report back
[ ] @Rhea G What would useful documentation for gt4py look like?

Review of action points of last meeting:

[x] @Johann D Will update regions GDP language to match implementation
[x] @Rhea G + @Oliver E read through https://github.com/GridTools/concepts/wiki/GTScript-Parallel-model and give feedback from implementation-land

[x] Submit items for mini-workshop in this document:
- https://docs.google.com/document/d/1hFQ0TfO7fAiz7Xh-LE3RQucesI_k0tuCGku6pmz9qnY/edit (outdated)
- https://hackmd.io/@egparedes/Bkf7qxibv
[ ] @Tobias W, @Oli F Present outcome of HPC4WC student projects (once they are graded) — carried over to this time

Discussion Points

Testing of gt4py [@Oli F]

Currently only internal backend are tested on CPU on github.com/gridtools/gt4py.
VCM would like to extend testing to GPU and Piz Daint.
How to proceed?

Proof of concept working

Closure: make stage with extents issue [@Eddie D]

https://github.com/GridTools/gt4py/issues/143

Meant to resolve GridTools/gt4py#143

We need to make separate multistages for fields written back to themselves with a horizontal extent. This check used to exist in an older version of the pipeline, but was since removed. We need to put back a fix to not merge multistages when this pattern exists.

Assignee: @Eddie D

Reduced field dimensions [@Eddie D]

Reduce temporary field dimensions if not used between multistages and k extent is 0.
Changed axes in fielddecl to IJ
Workaround: Changing shape to 1 in these dimensions (thus index to 0)

Regions [@Johann D]

Update: python backends working, need gridtools support
Initial review — @Enrique G. P
Settled on using with horizontal(region[:, js:je])

We’re removing the PARALLEL keyword in computation(...)!

Stencil Workshop Follow-up [@Enrique]

@Enrique G. P cleaned up the workshop document
Tasks will be created and planned there

Point to add: Change computation to vertical

Discuss: temporaries in conditionals [@Tobias W]

Specifically if conditions make us split computations into multiple stencils
Problem: run-time conditionals

Parallel model feedback [@Rhea G, @Oliver E]

See +GT4Py Parallel Model thoughts .

Discuss: definition of conditionals in the parallel model [@Enrique G. P @Hannes]

2 way of defining this: whole block or each statement is wrapped in a parallel for loop

Documentation [@Oli F]

Where are new features (e.g. regions) documented? GDP? Should we plan a Hackathon where we aim for more documentation? Priority? Format?