Generalised loop tiling with examples

[mn416]

This PR generalises LoopTiling2DTrans to LoopTilingTrans by lifting restrictions on the number of dimensions of the tile and the sizes of those dimensions (they no longer have to be uniform). For backwards compatibility, LoopTiling2DTrans remains but is now defined in terms of LoopTilingTrans.

This work was motivated by a simple example I was exploring for learning purposes: accelerating the matrix multiplication loop, which benefits from 3D tiling. This example is included in the PR, as well as a simpler example for matrix transposition, which only involves 2D tiling.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.90%. Comparing base (773f0c8) to head (691664e).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3039   +/-   ##
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  Coverage   99.90%   99.90%           
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  Files         370      371    +1     
  Lines       52055    52085   +30     
=======================================
+ Hits        52005    52035   +30     
  Misses         50       50           

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[sergisiso]

Thanks for contributing this @mn416, I gave you permissions to modify labels (you should recieve an invite). Add a test for the missing Code Coverage line and then mark this PR with the "Ready for Review" label.

[hiker]

Thanks a lot for this, I have been wanting to implement something like your work forever :)

Besides the comment here (sorry, you are suffering a bit from a change of coding style and our 'you touch it, you update it' :) ), two more basic questions:

1. Wouldn't it be a lot easier if the old 2d implementation would inherit directly from your new transpose (and just provides the right dimension sizes)
2. You renamed the name of the tiling option (tilesize before, tiledims now). I think it would be easier if you could use the same name (tiledims). This would make it easier to replace (at some time in the future) to deprecate the old implemenation entirely. Also, if the same names would be used and you use the inherit as suggested, you remove a lot of code duplication in the validation checks for the parameters.

[hiker]

@arporter, @sergisiso - I am wondering if we could consider either removing the old 2d-only tiling (which would require some small changes to existing scripts), or at least deprecating it (i.e. warning, but still works)?

[sergisiso]

I am wondering if we could consider either removing the old 2d-only tiling

I am in favour of removing it (without a deprecation notice/period) since it is currently not being used in any production application.

[mn416]

Thank you very much @hiker for the review. I am AFK for the rest of this week, but will respond and make the fixes next week, all being well.

[hiker]

Thank you very much @hiker for the review. I am AFK for the rest of this week, but will respond and make the fixes next week, all being well.

No rush, I have a few days off myself as well :)

[mn416]

Thanks @hiker and @sergisiso. I've dropped loop_tiling_2d_trans.py and moved to the new way of handling transformation options. I believe I've addressed all the review comments too.

[hiker]

An additional comment: we discussed this PR in our last telco, and agreed that we are happy to replace the old 2d transformation long term. Since we are not certain if people are using the 2d transformation, we don't want to just break compatibility with the next release, Could you add a depreciation warning to the 2d transformation as well?

[sergisiso]

We just said in the previous comment that we would delete it :) I am fairly sure nobody uses it, and the update is very simple. I think we are just adding unnecessary complexity to keeping it around.

[mn416]

@sergisiso I just added it back (with a deprecation warning) before I saw your comment! But it's easy for me to delete it again. @hiker can you confirm whether you would like LoopTiling2DTrans in or out? Thanks!

[hiker]

I'm bringing this up-to-master, and will then trigger the CI.

[hiker]

CI passed, all issues addressed. Proceeding to merge.