Differentiable Fortran with LFortran and Enzyme

Discussion (4 Comments)Read Original on HackerNews

dionhaefner•about 3 hours ago

Author here — I work on Tesseract at Pasteur Labs, and I wrote this up because the "what if this was possible" was bugging me for way too long :)

I was surprised by how well this worked, the LFortran + Enzyme stack seems to be a very clean way to get gradients through Fortran code via LLVM IR transformations. Pretty cool to see a 220-line Fortran heat solver turn into ~6,900-line reverse pass automatically if I dare say so.

Would be awesome to see this applied to a real scientific codebase, and I hope that the demo is enough to convince people that it’s worth trying.

srean•about 1 hour ago

Very interesting. Does LFortran have the same internal array layout as the standard C runtime ?

A shared layout and a shared calling convention would be very nice.

Sorry about my naive question. Haven't touched Fortran directly in three decades I think.

EDIT: thanks for your reply. For some reason it has been flagged dead. So am responding here. You can mail dang hn at ycombinator dot co m about the flagging. He is very nice.

wombatpm•about 1 hour ago

Lots of scientific code in Fortran has sparse arrays, so a NxN array that only has values on 5 diagonals will store that as 5xN array to save memory allowing you to run a larger problem.

srean•about 1 hour ago

That's a very orthogonal issue.

Sparse arrays are supported on C libraries too. I have done my time with CSC and CSR even inside Python that called out to C libraries.

Differentiable Fortran with LFortran and Enzyme

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Discussion (4 Comments)Read Original on HackerNews