[Enhancement] Support gather operation in NCCL backend #1061
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
HAOCHENYE
reviewed
Apr 10, 2023
There was a problem hiding this comment.
Hi, Thanks for your contribution! We should update the unit test here to verify the modification works as expected.
Besides, PyTorch has already supported gather in nccl since version 1.11, and we should also take it into account.
add pytorch version condition
zhouzaida
reviewed
Apr 10, 2023
mmengine/dist/dist.py
Outdated
| torch_dist.gather(data, gather_list, dst, group) | ||
| else: | ||
| if get_rank(group) == dst: | ||
| gather_list = torch.cuda.comm.gather(data, dst, group) |
There was a problem hiding this comment.
Hi, torch.cuda.comm.gather only supports single-node. Can we use all_gather to implement it as a workaround?
|
Hi, @sh0622-kim, you can use |
HAOCHENYE
reviewed
Apr 26, 2023
| gather_list = all_gather_list | ||
| else: | ||
| gather_list = [] | ||
| gather_list = all_gather(data, group) |
There was a problem hiding this comment.
all_gather should be called at all ranks otherwise the program will be blocked. We should only return the gathered list at the main rank, and return an empty list at other ranks.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.
Motivation
I wanted to help with the work in #916.
Modification
Supports gather operation for NCCL backend.
Checklist