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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.
from typing import Union
import torch
from typing_extensions import override
from lightning_fabric.accelerators.accelerator import Accelerator
from lightning_fabric.accelerators.registry import _AcceleratorRegistry
class CPUAccelerator(Accelerator):
"""Accelerator for CPU devices."""
@override
def setup_device(self, device: torch.device) -> None:
"""
Raises:
ValueError:
If the selected device is not CPU.
"""
if device.type != "cpu":
raise ValueError(f"Device should be CPU, got {device} instead.")
@override
def teardown(self) -> None:
pass
@staticmethod
@override
def parse_devices(devices: Union[int, str]) -> int:
"""Accelerator device parsing logic."""
return _parse_cpu_cores(devices)
@staticmethod
@override
def get_parallel_devices(devices: Union[int, str]) -> list[torch.device]:
"""Gets parallel devices for the Accelerator."""
devices = _parse_cpu_cores(devices)
return [torch.device("cpu")] * devices
@staticmethod
@override
def auto_device_count() -> int:
"""Get the devices when set to auto."""
return 1
@staticmethod
@override
def is_available() -> bool:
"""CPU is always available for execution."""
return True
@classmethod
@override
def register_accelerators(cls, accelerator_registry: _AcceleratorRegistry) -> None:
accelerator_registry.register(
"cpu",
cls,
description=cls.__name__,
)
def _parse_cpu_cores(cpu_cores: Union[int, str]) -> int:
"""Parses the cpu_cores given in the format as accepted by the ``devices`` argument in the
:class:`~pytorch_lightning.trainer.trainer.Trainer`.
Args:
cpu_cores: An int > 0 or a string that can be converted to an int > 0.
Returns:
An int representing the number of processes
Raises:
MisconfigurationException:
If cpu_cores is not an int > 0
"""
if isinstance(cpu_cores, str) and cpu_cores.strip().isdigit():
cpu_cores = int(cpu_cores)
if not isinstance(cpu_cores, int) or cpu_cores <= 0:
raise TypeError("`devices` selected with `CPUAccelerator` should be an int > 0.")
return cpu_cores
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