Fix ZeRO-3 autocast gather with mixed parameter dtypes#8113
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Signed-off-by: Masahiro Tanaka <mtanaka@anyscale.com>
Signed-off-by: Masahiro Tanaka <mtanaka@anyscale.com>
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This PR allows ZeRO-3 coalesced all-gather buckets to contain parameters with different original dtypes when they share the same autocast communication dtype.
Motivation: PEFT-style LoRA adapters can remain FP32 trainable parameters while the base model parameters are BF16. When DeepSpeed autocast marks both sets of parameters for BF16 communication, the existing assertion still checks their original parameter dtypes and fails on the BF16/FP32 mismatch. With this PR, LoRA-style FP32 adapter parameters can participate in BF16 autocast communication without requiring applications to pre-cast the adapters to BF16.