deepspeedai / deepspeedai/DeepSpeed

Details about backward hooks in stage3, why detach outputs?

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Description

Dear authors,

Thank you for the awesome works. I try to learn some implementation details and come across a small question.
I doubt the meaning of the two following lines. I believe it is the same if you remove two lines and in this way, you may save some tmp memory.
https://github.com/microsoft/DeepSpeed/blob/master/deepspeed/runtime/zero/stage3.py#L503
https://github.com/microsoft/DeepSpeed/blob/master/deepspeed/runtime/zero/stage3.py#L528

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Research direction

Start by reading the linked lines in deepspeed/runtime/zero/stage3.py, especially the backward-hook handling around lines 503 and 528. Trace how the detached outputs are used and compare the behavior with those lines removed; done means establishing whether removing them preserves behavior and documenting the conclusion.

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Assessment

Tech stack
python
Domain
distributed-systems, machine-learning
Issue type
Refactor
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
30/100

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