Make models amenable to scan #157
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We replace the `for` loop in both Llama and Mixtral with an equivalent `HomogenousSequential` layer, which can be either run a for loop or use `torch_xla`'s scan operator. This is a clean-ish way to turn scan on/off without cluttering the modeling code. I also adjusted Mixtral slightly so that we can even run `scan` in Mixtral with its static MoE implementation. Scanning over GMM on the other hand won't work until GMM forward/backward is wrapped in a custom op similar to pytorch/xla#8654. Test: added unit test. Next PR will change the trainer to apply scan.
bhavya01
reviewed
Mar 17, 2025
zpcore
reviewed
Mar 17, 2025
zpcore
reviewed
Mar 17, 2025
zpcore
reviewed
Mar 17, 2025
zpcore
reviewed
Mar 17, 2025
bhavya01
approved these changes
Mar 17, 2025
zpcore
reviewed
Mar 18, 2025
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@zpcore i saw you added a number of comments but didn't press "Request Changes" or "Approve" -- let me know if you would like to request changes or approve. |
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We replace the
forloop in both Llama and Mixtral with an equivalentHomogenousSequentiallayer, which can be either run a for loop or usetorch_xla's scan operator. This is a clean-ish way to turn scan on/off without cluttering the modeling code.I also adjusted Mixtral slightly so that we can even run
scanin Mixtral with its static MoE implementation. In order to integrate with scan, we need to refactor the Mixtral decoder for loop into a format where results from the previous iteration feed into the next iteration. Scanning over GMM on the other hand won't work until GMM forward/backward is wrapped in a custom op similar to pytorch/xla#8654.Cleanup the README that got jumbled in #111 while I'm here.
Test: added unit test. Next PR will change the trainer to apply scan.