Source code for lightning.pytorch.plugins.precision.fsdp
# Copyright The Lightning AI team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Any, Literal, Optional
import torch
from lightning.fabric.utilities.imports import _TORCH_GREATER_EQUAL_1_12
from lightning.pytorch.plugins.precision.amp import MixedPrecisionPlugin
from lightning.pytorch.utilities.exceptions import MisconfigurationException
if _TORCH_GREATER_EQUAL_1_12 and torch.distributed.is_available():
from torch.distributed.fsdp.fully_sharded_data_parallel import MixedPrecision
from torch.distributed.fsdp.sharded_grad_scaler import ShardedGradScaler
else:
MixedPrecision = None # type: ignore[misc,assignment]
ShardedGradScaler = None # type: ignore[misc,assignment]
[docs]class FSDPMixedPrecisionPlugin(MixedPrecisionPlugin):
"""AMP for Fully Sharded Data Parallel (FSDP) Training.
.. warning:: This is an :ref:`experimental <versioning:Experimental API>` feature.
"""
def __init__(
self, precision: Literal["16-mixed", "bf16-mixed"], device: str, scaler: Optional[ShardedGradScaler] = None
) -> None:
if not _TORCH_GREATER_EQUAL_1_12:
raise MisconfigurationException("`FSDPMixedPrecisionPlugin` is supported from PyTorch v1.12.0 onwards.")
super().__init__(
precision, device, scaler=(ShardedGradScaler() if scaler is None and str(precision) == "16-mixed" else None)
)
[docs] def clip_grad_by_norm(self, *_: Any, **__: Any) -> None:
# see https://pytorch.org/docs/stable/fsdp.html#torch.distributed.fsdp.FullyShardedDataParallel.clip_grad_norm_
# section `Gradient Clipping`, using `torch.nn.utils.clip_grad_norm_` is incorrect
# for FSDP module. To overcome this, needs to call sharded_module.clip_grad_norm(clip_val)
# however we rely on LightningModule's configure_sharded_model to wrap FSDP, it would be hard to
# trace back the root FSDP. Now we only support clip by value.
raise MisconfigurationException(
f"`gradient_clip_algorithm='norm'` is currently not supported for `{self.__class__.__name__}`"
)
@property
def mixed_precision_config(self) -> Optional[MixedPrecision]:
assert MixedPrecision is not None
if self.precision == "16-mixed":
dtype = torch.float16
elif self.precision == "bf16-mixed":
dtype = torch.bfloat16
else:
raise MisconfigurationException(f"Was unable to infer precision type, received {self.precision!r}.")
return MixedPrecision(
param_dtype=dtype,
reduce_dtype=dtype,
buffer_dtype=dtype,
)