[v1.7 patch] Disallow creation of ProcessGroupNCCL without GPUs. (#45… #46073
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) Summary: Note: This PR has been merged into master at b5a2f04 after the 1.7 branch cut (see original PR: #45642). This PR is to merge it into the 1.7 branch. ---- Original Commit Description Follows --- Pull Request resolved: #45642 Prior to #45181, initializing a NCCL process group would work even if no GPUs were present. Although, now since init_process_group calls `barrier()` this would fail. In general the problem was that we could initialize ProcessGroupNCCL without GPUs and then if we called a method like `barrier()` the process would crash since we do % numGPUs resulting in division by zero. ghstack-source-id: 113490343 Test Plan: waitforbuildbot Reviewed By: osalpekar Differential Revision: D24038839 fbshipit-source-id: a1f1db52cabcfb83e06c1a11ae9744afbf03f8dc
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This was referenced Oct 9, 2020
Codecov Report
@@ Coverage Diff @@
## release/1.7 #46073 +/- ##
===============================================
- Coverage 68.46% 68.46% -0.01%
===============================================
Files 406 406
Lines 52267 52275 +8
===============================================
+ Hits 35785 35790 +5
- Misses 16482 16485 +3
Continue to review full report at Codecov.
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malfet
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Oct 12, 2020
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Summary:
Note: This PR has been merged into master at b5a2f04 after the 1.7 branch cut
(see original PR: #45642). This PR is to merge it into the 1.7 branch.
---- Original Commit Description Follows ---
Pull Request resolved: #45642
Prior to #45181, initializing a
NCCL process group would work even if no GPUs were present. Although, now since
init_process_group calls
barrier()this would fail.In general the problem was that we could initialize ProcessGroupNCCL without
GPUs and then if we called a method like
barrier()the process would crashsince we do % numGPUs resulting in division by zero.
ghstack-source-id: 113490343
Test Plan: waitforbuildbot
Reviewed By: osalpekar
Differential Revision: D24038839
fbshipit-source-id: a1f1db52cabcfb83e06c1a11ae9744afbf03f8dc