Cause (Documented platform behavior): FSDP2 checks for meta params at lazy init.
Fix status: documented_behavior
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/pytorch/pytorch/4b0647edace7000cd959f43b857da716d06247c9/torch/distributed/fsdp/_fully_shard/_fsdp_param_group.py (official_docs, unknown, documented_behavior): Meta and CPU-offload materialization errors with guidance.
Search phrasings: FSDP parameters should be materialized from meta device before training; fully_shard meta device to_empty reset_parameters
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- First forward raises listing meta params.
- Context
- Product: PyTorch FSDP2 (fully_shard) Component: FSDPParamGroup lazy init Operation: Meta-device model init (torch.device("meta")) + fully_shard, then forward Affected versions: unknown Environment: unknown Exception: RuntimeError Packages: torch main at pinned SHA Trigger: Skipping module.to_empty(device=...) and parameter init (or loading a state dict) after sharding.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- FSDP parameters should be materialized from meta device before training, but the following were still on meta device:
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [FSDP2] "FSDP parameters should be materialized from meta device before training" - meta-device init without to_empty/reset_parameters
Recommended action: After fully_shard: model.to_empty(device="cuda"); call reset_parameters()/init weights or load a (distributed) state dict; with CPU offload use to_empty(device="cpu").
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 58c95fe3-77bd-424b-8ea3-2beec5974300
- Proposed action
- Recommended action: After fully_shard: model.to_empty(device="cuda"); call reset_parameters()/init weights or load a (distributed) state dict; with CPU offload use to_empty(device="cpu").
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.