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Fix 8gpu PP failure due to 2D DCP disablement #460

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merged 1 commit into from
Jul 26, 2024
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Fix 8gpu PP failure due to 2D DCP disablement #460

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11 changes: 11 additions & 0 deletions torchtitan/parallelisms/parallelize_llama.py
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Original file line number Diff line number Diff line change
Expand Up @@ -484,6 +484,17 @@ def apply_dp(
model, **fsdp_config, reshard_after_forward=not parallel_dims.pp_enabled
)

if parallel_dims.pp_enabled:
# TODO
# This PR https://github.com/pytorch/pytorch/pull/129519 added a safety check to avoid using 2D/3D DCP since
# without strided sharding, DCP can not safely support resharding for 2D/3D. However, for PP to work, even
# without resharding, we load a seed-checkpoint and need to disable the safety mechanism. This hack should be
# removed after strided sharding is landed in DCP.
for module in model.modules():
assert len(module._load_state_dict_pre_hooks) <= 1
module._load_state_dict_pre_hooks.clear()
assert len(module._state_dict_pre_hooks) <= 1
module._state_dict_pre_hooks.clear()
logger.info("Applied FSDP to the model")
return model

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