Fix reducescatter() and grouped_reducescatter() to raise clean exceptions for scalar inputs #3699
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Unit Test Results (with flaky tests) 1 254 files - 6 1 254 suites - 6 11h 28m 38s ⏱️ - 56m 33s For more details on these failures and errors, see this check. Results for commit 8451913. ± Comparison against base commit 427b633. ♻️ This comment has been updated with latest results. |
…ions for scalar inputs Signed-off-by: Max H. Gerlach <git@maxgerlach.de>
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Signed-off-by: Max H. Gerlach <git@maxgerlach.de>
romerojosh
approved these changes
Sep 19, 2022
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LGTM @maxhgerlach! I introduced a conflict merging in another PR, but once that is resolved, good to merge.
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Thanks @romerojosh |
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Description
This fixes Horovod crashing when scalar inputs are passed to
hvd.reducescatterorhvd.grouped_reducescatter. Attempts to do so now raise exceptions that users can deal with appropriately.Initially I thought it would be a good idea to have
hvd.reducescatter(3.14)do exactly the same thing ashvd.reducescatter([3.14]), i.e., return a single-element 1D tensor on rank 0 and an empty 1D tensor on the other ranks. However, having given this some consideration, I feel that it would be confusing and potentially error prone if zero-rank inputs produced higher ranked outputs. It seems less surprising to deal with such a possibility explicitly in user code if necessary (just as it is the case withhvd.allgather).Fixes #3698.