Fix FSDP mixed precision semantics and add user warning #21361
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deependujha
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #21361 +/- ##
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- Coverage 87% 87% -0%
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Files 269 269
Lines 23744 23736 -8
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- Hits 20572 20561 -11
- Misses 3172 3175 +3 |
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| if precision != "32-true": | ||
| rank_zero_warn( | ||
| f"FSDPPrecision `{precision}` runs computations in reduced precision " | ||
| "(e.g., float16/bfloat16) while keeping model weights stored in full precision. " | ||
| "These modes are still experimental and may produce slightly different accuracy or stability " | ||
| "compared to full precision (`precision='32-true'`)." | ||
| ) |
| param_dtype = torch.float32 | ||
| reduce_dtype = buffer_dtype = torch.bfloat16 | ||
| elif self.precision == "16-true": | ||
| if self.precision in ("16-true", "16-mixed"): |
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let's instead add a warning here for 16-true and bf16-true that fsdp always keeps a full precision reference of the weights
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What does this PR do?
Fixes #<issue_number>
Align FSDP "-mixed" precision modes with their "-true" counterparts, since parameters remain in full precision. Adds a warning for all reduced-precision modes indicating experimental status.
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📚 Documentation preview 📚: https://pytorch-lightning--21361.org.readthedocs.build/en/21361/