MAINT: Simplify NCCL worker rank identification #2228
Merged
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
|
@cjnolet , Would it be possible to get an okay to test comment here please. Want to understand why it will break on CI . |
|
/ok to test |
2 similar comments
|
/ok to test |
|
/ok to test |
|
@VibhuJawa could you please squash the commits so there is one signed commit? That should fix the CI issues here |
This is a follow up on rapidsaigh-1926, since the rank sorting seemed a bit hard to understand. It does modify the logic in the sense that the host is now sorted by IP as a way to group based on it. But I don't really think that host sorting was ever a goal? If the goal is really about being deterministic, then this should be more (or at least clearer) deterministic about order of worker IPs. OTOH, if the NVML device order doesn't matter, we could just sort the workers directly. The original rapidsaigh-1587 mentions: NCCL>1.11 expects a process with rank r to be mapped to r % num_gpus_per_node which is something that neither approach seems to quite assure, if such a requirement exists, I would want to do one of: * Ensure we can guarantee this, but this requires initializing workers that are not involved in the operation. * At least raise an error, because if NCCL will end up raising the error it will be very confusing.
VibhuJawa
force-pushed
the
simplify-nccl-index
branch
from
bfb1116
to
296c922
Compare
VibhuJawa
changed the title
cjnolet
approved these changes
Mar 15, 2024
|
/merge |
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Outdated suggestions cannot be applied.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.
This PR is based on @seberg work in #1928 .
From the PR:
This is a follow up on #1926, since the rank sorting seemed a bit hard to understand.
It does modify the logic in the sense that the host is now sorted by IP as a way to group based on it. But I don't really think that host sorting was ever a goal?
If the goal is really about being deterministic, then this should be more (or at least clearer) deterministic about order of worker IPs.
OTOH, if the NVML device order doesn't matter, we could just sort the workers directly.
The original #1587 mentions:
NCCL>1.11 expects a process with rank r to be mapped to r % num_gpus_per_node
which is something that neither approach seems to quite assure, if such a requirement exists, I would want to do one of:
Ensure we can guarantee this, but this requires initializing workers that are not involved in the operation.
At least raise an error, because if NCCL will end up raising the error it will be very confusing.