pymc-devs / pymc-devs/pytensor
IncSubtensor causes graph break in pytorch backend
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- Dominant language
- Python
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- Avg merge
- 2d 14h
- Merged PRs (30d)
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Description
Description
import pytensor
import pytensor.tensor as pt
import torch
x = pt.vector('x')
y = x[-1].inc(1)
f = pytensor.function(inputs=[x], outputs=y, mode="PYTORCH")
torch._dynamo.explain(f.vm.jit_fn._fn)(torch.zeros(2)).break_reasons
WIll produce: [GraphCompileReason(reason='data dependent operator: aten._local_scalar_dense.default; to enable, set torch._dynamo.config.capture_scalar_outputs = True', user_stack=[<FrameSummary file [/Users/ch0ronomato/dev/pytensor/pytensor/link/pytorch/dispatch/subtensor.py](https://file+.vscode-resource.vscode-cdn.net/Users/ch0ronomato/dev/pytensor/pytensor/link/pytorch/dispatch/subtensor.py), line 99 in inc_subtensor>], graph_break=True)]
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Research direction
Run the PyTensor/PyTorch reproducer from the issue and inspect pytensor/link/pytorch/dispatch/subtensor.py around line 99 in inc_subtensor. Use torch._dynamo.explain on the compiled function to verify the graph break and trace the relevant dispatch behavior. Done means the reproducer no longer reports this graph break.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python, pytorch
- Domain
- backend, machine-learning
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100