# Copyright 2020 The HuggingFace Team. All rights reserved.
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# 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 math
from collections import OrderedDict
import torch
from packaging import version
from torch import Tensor, nn
from .utils import logging
logger = logging.get_logger(__name__)
class PytorchGELUTanh(nn.Module):
"""
A fast C implementation of the tanh approximation of the GeLU activation function. See
https://arxiv.org/abs/1606.08415.
This implementation is equivalent to NewGELU and FastGELU but much faster. However, it is not an exact numerical
match due to rounding errors.
"""
def __init__(self):
super().__init__()
if version.parse(torch.__version__) < version.parse("1.12.0"):
raise ImportError(
f"You are using torch=={torch.__version__}, but torch>=1.12.0 is required to use "
"PytorchGELUTanh. Please upgrade torch."
)
def forward(self, input: Tensor) -> Tensor:
return nn.functional.gelu(input, approximate="tanh")
class NewGELUActivation(nn.Module):
"""
Implementation of the GELU activation function currently in Google BERT repo (identical to OpenAI GPT). Also see
the Gaussian Error Linear Units paper: https://arxiv.org/abs/1606.08415
"""
def forward(self, input: Tensor) -> Tensor:
return 0.5 * input * (1.0 + torch.tanh(math.sqrt(2.0 / math.pi) * (input + 0.044715 * torch.pow(input, 3.0))))
class GELUActivation(nn.Module):
"""
Original Implementation of the GELU activation function in Google BERT repo when initially created. For
information: OpenAI GPT's GELU is slightly different (and gives slightly different results): 0.5 * x * (1 +
torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3)))) This is now written in C in nn.functional
Also see the Gaussian Error Linear Units paper: https://arxiv.org/abs/1606.08415
"""
def __init__(self, use_gelu_python: bool = False):
super().__init__()
if use_gelu_python:
self.act = self._gelu_python
else:
self.act = nn.functional.gelu
def _gelu_python(self, input: Tensor) -> Tensor:
return input * 0.5 * (1.0 + torch.erf(input / math.sqrt(2.0)))
def forward(self, input: Tensor) -> Tensor:
return self.act(input)
class FastGELUActivation(nn.Module):
"""
Applies GELU approximation that is slower than QuickGELU but more accurate. See: https://github.com/hendrycks/GELUs
"""
def forward(self, input: Tensor) -> Tensor:
return 0.5 * input * (1.0 + torch.tanh(input * 0.7978845608 * (1.0 + 0.044715 * input * input)))
class QuickGELUActivation(nn.Module):
"""
Applies GELU approximation that is fast but somewhat inaccurate. See: https://github.com/hendrycks/GELUs
"""
def forward(self, input: Tensor) -> Tensor:
return input * torch.sigmoid(1.702 * input)
class ClippedGELUActivation(nn.Module):
"""
Clip the range of possible GeLU outputs between [min, max]. This is especially useful for quantization purpose, as
it allows mapping negatives values in the GeLU spectrum. For more information on this trick, please refer to
https://arxiv.org/abs/2004.09602.
Gaussian Error Linear Unit. Original Implementation of the gelu activation function in Google Bert repo when
initially created.
For information: OpenAI GPT's gelu is slightly different (and gives slightly different results): 0.5 * x * (1 +
torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3)))). See https://arxiv.org/abs/1606.08415
"""
def __init__(self, min: float, max: float):
if min > max:
raise ValueError(f"min should be < max (got min: {min}, max: {max})")
super().__init__()
self.min = min
self.max = max
def forward(self, x: Tensor) -> Tensor:
return torch.clip(gelu(x), self.min, self.max)
class AccurateGELUActivation(nn.Module):
"""
Applies GELU approximation that is faster than default and more accurate than QuickGELU. See:
https://github.com/hendrycks/GELUs
Implemented along with MEGA (Moving Average Equipped Gated Attention)
"""
def __init__(self):
super().__init__()
self.precomputed_constant = math.sqrt(2 / math.pi)
def forward(self, input: Tensor) -> Tensor:
return 0.5 * input * (1 + torch.tanh(self.precomputed_constant * (input + 0.044715 * torch.pow(input, 3))))
class SiLUActivation(nn.Module):
"""
See Gaussian Error Linear Units (Hendrycks et al., https://arxiv.org/abs/1606.08415) where the SiLU (Sigmoid Linear
Unit) was originally introduced and coined, and see Sigmoid-Weighted Linear Units for Neural Network Function
Approximation in Reinforcement Learning (Elfwing et al., https://arxiv.org/abs/1702.03118) and Swish: a Self-Gated
Activation Function (Ramachandran et al., https://arxiv.org/abs/1710.05941v1) where the SiLU was experimented with
later.
"""
def forward(self, input: Tensor) -> Tensor:
return nn.functional.silu(input)
class MishActivation(nn.Module):
"""
See Mish: A Self-Regularized Non-Monotonic Activation Function (Misra., https://arxiv.org/abs/1908.08681). Also
visit the official repository for the paper: https://github.com/digantamisra98/Mish
"""
def __init__(self):
super().__init__()
if version.parse(torch.__version__) < version.parse("1.9.0"):
self.act = self._mish_python
else:
self.act = nn.functional.mish
def _mish_python(self, input: Tensor) -> Tensor:
return input * torch.tanh(nn.functional.softplus(input))
def forward(self, input: Tensor) -> Tensor:
return self.act(input)
class LinearActivation(nn.Module):
"""
Applies the linear activation function, i.e. forwarding input directly to output.
"""
def forward(self, input: Tensor) -> Tensor:
return input
class LaplaceActivation(nn.Module):
"""
Applies elementwise activation based on Laplace function, introduced in MEGA as an attention activation. See
https://arxiv.org/abs/2209.10655
Inspired by squared relu, but with bounded range and gradient for better stability
"""
def forward(self, input, mu=0.707107, sigma=0.282095):
input = (input - mu).div(sigma * math.sqrt(2.0))
return 0.5 * (1.0 + torch.erf(input))
class ReLUSquaredActivation(nn.Module):
"""
Applies the relu^2 activation introduced in https://arxiv.org/abs/2109.08668v2
"""
def forward(self, input):
relu_applied = nn.functional.relu(input)
squared = torch.square(relu_applied)
return squared
class ClassInstantier(OrderedDict):
def __getitem__(self, key):
content = super().__getitem__(key)()
cls, kwargs = content if isinstance(content, tuple) else (content, {})
return cls(**kwargs)
ACT2CLS = {
"gelu": lambda: GELUActivation,
"gelu_10": lambda: (ClippedGELUActivation, {"min": -10, "max": 10}),
"gelu_fast": lambda: FastGELUActivation,
"gelu_new": lambda: NewGELUActivation,
"gelu_python": lambda: (GELUActivation, {"use_gelu_python": True}),
"gelu_pytorch_tanh": lambda: PytorchGELUTanh,
"gelu_accurate": lambda: AccurateGELUActivation,
"laplace": lambda: LaplaceActivation,
"linear": lambda: LinearActivation,
"mish": lambda: MishActivation,
"quick_gelu": lambda: QuickGELUActivation,
"relu": lambda: nn.ReLU,
"relu2": lambda: ReLUSquaredActivation,
"relu6": lambda: nn.ReLU6,
"sigmoid": lambda: nn.Sigmoid,
"silu": lambda: SiLUActivation,
"swish": lambda: SiLUActivation,
"tanh": lambda: nn.Tanh,
}
ACT2FN = ClassInstantier(ACT2CLS)
def get_activation(activation_string):
if activation_string in ACT2FN:
return ACT2FN[activation_string]
else:
raise KeyError(f"function {activation_string} not found in ACT2FN mapping {list(ACT2FN.keys())}")
# For backwards compatibility with: from activations import gelu_python
gelu_python = get_activation("gelu_python")
gelu_new = get_activation("gelu_new")
gelu = get_activation("gelu")
gelu_fast = get_activation("gelu_fast")
quick_gelu = get_activation("quick_gelu")
silu = get_activation("silu")
mish = get_activation("mish")
linear_act = get_activation("linear")