Lightning-AI / Lightning-AI/lightning-thunder

Implement VJP for `python_print`

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Dominant language
Python
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Description

🚀 Feature

Motivation

Enable debugging

Pitch
import torch
import thunder
from thunder.core.prims import python_print

def fn(x):
    y = x + 2
    python_print(y)
    return y

x = torch.randn(2, requires_grad=True)
cfn = thunder.jit(fn)
y = cfn(x)
NotImplementedError: VJP for PrimIDs.PRINT is not implemented

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start at thunder.core.prims.python_print and trace the VJP dispatch that reports PrimIDs.PRINT as unimplemented. Use the provided thunder.jit example to verify that the printed value still works with a tensor requiring gradients and that the VJP error no longer occurs.

Written by the indexing model from the issue text.

Assessment

Tech stack
python, pytorch
Domain
compilers, machine-learning
Issue type
Feature
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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