Lightning-AI / Lightning-AI/lightning-thunder

avoid joint trace in rematerialize forward backward

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rematerialization
Dominant language
Python
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Description

In #1615 we had to temporarily disable rematerialization because it seems to generate funny flow graphs when symbols are duplicate. We re-enabled it in #1622, but it may be more robust to not need to do the joint trace but instead construct the graph and then process the forward and (in particular) backward separately.

cc @riccardofelluga

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Research direction

Start by reading issues #1615 and #1622 to understand the rematerialization regression and its re-enablement. Then trace the joint-trace path described here and investigate how the graph could be constructed before separately processing forward and backward. Done means rematerialization remains enabled without producing incorrect flow graphs when symbols are duplicated.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
compilers
Issue type
Refactor
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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