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# 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.
import os
from typing import Any, Literal
import torch
from typing_extensions import get_args, override
from lightning.fabric.accelerators.xla import _XLA_AVAILABLE
from lightning.fabric.plugins.precision.precision import Precision
from lightning.fabric.utilities.types import Optimizable
_PRECISION_INPUT = Literal["32-true", "16-true", "bf16-true"]
class XLAPrecision(Precision):
"""Plugin for training with XLA.
Args:
precision: Full precision (32-true) or half precision (16-true, bf16-true).
Raises:
ValueError:
If unsupported ``precision`` is provided.
"""
def __init__(self, precision: _PRECISION_INPUT) -> None:
if not _XLA_AVAILABLE:
raise ModuleNotFoundError(str(_XLA_AVAILABLE))
supported_precision = get_args(_PRECISION_INPUT)
if precision not in supported_precision:
raise ValueError(
f"`precision={precision!r})` is not supported in XLA."
f" `precision` must be one of: {supported_precision}."
)
self.precision = precision
if precision == "16-true":
os.environ["XLA_USE_F16"] = "1"
self._desired_dtype = torch.float16
elif precision == "bf16-true":
os.environ["XLA_USE_BF16"] = "1"
self._desired_dtype = torch.bfloat16
else:
self._desired_dtype = torch.float32
@override
def optimizer_step(
self,
optimizer: Optimizable,
**kwargs: Any,
) -> Any:
import torch_xla.core.xla_model as xm
# you always want to `xm.mark_step()` after `optimizer.step` for better performance, so we set `barrier=True`
return xm.optimizer_step(optimizer, optimizer_args=kwargs, barrier=True)
@override
def teardown(self) -> None:
os.environ.pop("XLA_USE_BF16", None)
os.environ.pop("XLA_USE_F16", None)
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