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# Copyright 2024 MIT Han Lab | |
# | |
# 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. | |
# | |
# SPDX-License-Identifier: Apache-2.0 | |
import math | |
from typing import Union | |
import torch | |
from ...models.utils.list import val2list | |
__all__ = ["CosineLRwithWarmup", "ConstantLRwithWarmup"] | |
class CosineLRwithWarmup(torch.optim.lr_scheduler._LRScheduler): | |
def __init__( | |
self, | |
optimizer: torch.optim.Optimizer, | |
warmup_steps: int, | |
warmup_lr: float, | |
decay_steps: Union[int, list[int]], | |
last_epoch: int = -1, | |
) -> None: | |
self.warmup_steps = warmup_steps | |
self.warmup_lr = warmup_lr | |
self.decay_steps = val2list(decay_steps) | |
super().__init__(optimizer, last_epoch) | |
def get_lr(self) -> list[float]: | |
if self.last_epoch < self.warmup_steps: | |
return [ | |
(base_lr - self.warmup_lr) * (self.last_epoch + 1) / self.warmup_steps + self.warmup_lr | |
for base_lr in self.base_lrs | |
] | |
else: | |
current_steps = self.last_epoch - self.warmup_steps | |
decay_steps = [0] + self.decay_steps | |
idx = len(decay_steps) - 2 | |
for i, decay_step in enumerate(decay_steps[:-1]): | |
if decay_step <= current_steps < decay_steps[i + 1]: | |
idx = i | |
break | |
current_steps -= decay_steps[idx] | |
decay_step = decay_steps[idx + 1] - decay_steps[idx] | |
return [0.5 * base_lr * (1 + math.cos(math.pi * current_steps / decay_step)) for base_lr in self.base_lrs] | |
class ConstantLRwithWarmup(torch.optim.lr_scheduler._LRScheduler): | |
def __init__( | |
self, | |
optimizer: torch.optim.Optimizer, | |
warmup_steps: int, | |
warmup_lr: float, | |
last_epoch: int = -1, | |
) -> None: | |
self.warmup_steps = warmup_steps | |
self.warmup_lr = warmup_lr | |
super().__init__(optimizer, last_epoch) | |
def get_lr(self) -> list[float]: | |
if self.last_epoch < self.warmup_steps: | |
return [ | |
(base_lr - self.warmup_lr) * (self.last_epoch + 1) / self.warmup_steps + self.warmup_lr | |
for base_lr in self.base_lrs | |
] | |
else: | |
return self.base_lrs | |