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# Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved. | |
# Copyright 2022 The HuggingFace Team. All rights reserved. | |
# | |
# 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 paddle | |
from paddle import nn | |
class LitEma(nn.Layer): | |
""" | |
Exponential Moving Average (EMA) of model updates | |
Parameters: | |
model: The model architecture for apply EMA. | |
decay: The exponential decay. Default 0.9999. | |
use_num_updates: Whether to use number of updates when computing | |
averages. | |
""" | |
def __init__(self, model, decay=0.9999, use_num_upates=True): | |
super().__init__() | |
if decay < 0.0 or decay > 1.0: | |
raise ValueError("Decay must be between 0 and 1") | |
self.m_name2s_name = {} | |
self.register_buffer("decay", paddle.to_tensor(decay, dtype=paddle.float32)) | |
self.register_buffer( | |
"num_updates", | |
paddle.to_tensor(0, dtype=paddle.int64) if use_num_upates else paddle.to_tensor(-1, dtype=paddle.int64), | |
) | |
for name, p in model.named_parameters(): | |
if not p.stop_gradient: | |
# remove as '.'-character is not allowed in buffers | |
s_name = name.replace(".", "") | |
self.m_name2s_name.update({name: s_name}) | |
self.register_buffer(s_name, p.clone().detach()) | |
self.collected_params = [] | |
def forward(self, model): | |
decay = self.decay | |
if self.num_updates >= 0: | |
self.num_updates += 1 | |
decay = min(self.decay, (1 + self.num_updates) / (10 + self.num_updates)) | |
one_minus_decay = 1.0 - decay | |
with paddle.no_grad(): | |
m_param = dict(model.named_parameters()) | |
shadow_params = dict(self.named_buffers()) | |
for key in m_param: | |
if not m_param[key].stop_gradient: | |
sname = self.m_name2s_name[key] | |
shadow_params[sname].scale_(decay) | |
shadow_params[sname].add_(m_param[key] * one_minus_decay) | |
else: | |
assert key not in self.m_name2s_name | |
def copy_to(self, model): | |
m_param = dict(model.named_parameters()) | |
shadow_params = dict(self.named_buffers()) | |
for key in m_param: | |
if not m_param[key].stop_gradient: | |
m_param[key].copy_(shadow_params[self.m_name2s_name[key]], True) | |
else: | |
assert key not in self.m_name2s_name | |
def store(self, parameters): | |
""" | |
Save the current parameters for restoring later. | |
Args: | |
parameters: Iterable of `EagerParamBase`; the parameters to be | |
temporarily stored. | |
""" | |
self.collected_params = [param.clone() for param in parameters] | |
def restore(self, parameters): | |
""" | |
Restore the parameters stored with the `store` method. | |
Useful to validate the model with EMA parameters without affecting the | |
original optimization process. Store the parameters before the | |
`copy_to` method. After validation (or model saving), use this to | |
restore the former parameters. | |
Args: | |
parameters: Iterable of `EagerParamBase`; the parameters to be | |
updated with the stored parameters. | |
""" | |
for c_param, param in zip(self.collected_params, parameters): | |
param.copy_(c_param, True) | |