# megengine.module.activation 源代码

# -*- coding: utf-8 -*-
import numpy as np

from ..functional import gelu, leaky_relu, prelu, relu, sigmoid, silu, softmax
from ..tensor import Parameter
from .init import ones_, zeros_
from .module import Module

[文档]class Softmax(Module):
r"""Applies a softmax function. Softmax is defined as:

.. math::
\text{Softmax}(x_{i}) = \frac{exp(x_i)}{\sum_j exp(x_j)}

It is applied to all elements along axis, and rescales elements so that
they stay in the range [0, 1] and sum to 1.

Args:
axis: Along which axis softmax will be applied. By default,
softmax will be applyed along the highest ranked axis.

Shape:
- Input: :math:(*) where * means, any number of additional
dimensions
- Output: :math:(*), same shape as the input

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-2,-1,0,1,2]).astype(np.float32))
>>> softmax = M.Softmax()
>>> output = softmax(data)
>>> with np.printoptions(precision=6):
...     print(output.numpy())
[0.011656 0.031685 0.086129 0.234122 0.636409]
"""

def __init__(self, axis=None, **kwargs):
super().__init__(**kwargs)
self.axis = axis

def forward(self, inputs):
return softmax(inputs, self.axis)

def _module_info_string(self) -> str:
return "axis={axis}".format(axis=self.axis)

[文档]class Sigmoid(Module):
r"""Applies the element-wise function:

.. math::

\text{Sigmoid}(x) = \frac{1}{1 + \exp(-x)}

Shape:
*inputs: :math:(*) where :math:* means any member of addition dimensions.
*outpus: :math:(*) same shape as the inputs.

Returns:
Return type: module. The instance of the Sigmoid module.

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-2,-1,0,1,2,]).astype(np.float32))
>>> sigmoid = M.Sigmoid()
>>> output = sigmoid(data)
>>> with np.printoptions(precision=6):
...     print(output.numpy())
[0.119203 0.268941 0.5      0.731059 0.880797]
"""

def forward(self, inputs):
return sigmoid(inputs)

[文档]class SiLU(Module):
r"""Applies the element-wise function:

.. math::

\text{SiLU}(x) = \frac{x}{1 + \exp(-x)}

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-2,-1,0,1,2,]).astype(np.float32))
>>> silu = M.SiLU()
>>> output = silu(data)
>>> with np.printoptions(precision=6):
...     print(output.numpy())
[-0.238406 -0.268941  0.        0.731059  1.761594]
"""

def forward(self, inputs):
return silu(inputs)

[文档]class GELU(Module):
r"""Applies the element-wise function:

.. math::
\text{GELU}(x) = x\Phi(x)

where :math:\Phi(x) is the Cumulative Distribution Function for Gaussian Distribution.

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-2,-1,0,1,2,]).astype(np.float32))
>>> gelu = M.GELU()
>>> output = gelu(data)
>>> with np.printoptions(precision=4):
...     print(output.numpy())
[-0.0455 -0.1587  0.      0.8413  1.9545]
"""

def forward(self, inputs):
return gelu(inputs)

[文档]class ReLU(Module):
r"""Applies the rectified linear unit function element-wise:

.. math::
\text{ReLU}(x) = (x)^+ = \max(x, 0)

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-2,-1,0,1,2,]).astype(np.float32))
>>> relu = M.ReLU()
>>> output = relu(data)
>>> with np.printoptions(precision=6):
...     print(output.numpy())
[0. 0. 0. 1. 2.]
"""

def forward(self, x):
return relu(x)

[文档]class PReLU(Module):
r"""Applies the element-wise function:

.. math::
\text{PReLU}(x) = \max(0,x) + a * \min(0,x)

or

.. math::
\text{PReLU}(x) =
\begin{cases}
x, & \text{ if } x \geq 0 \\
ax, & \text{ otherwise }
\end{cases}

Here :math:a is a learnable parameter. When called without arguments, PReLU() uses
a single paramter :math:a across all input channel. If called with PReLU(num_of_channels), each input channle will has it's own :math:a.

Args:
num_parameters: number of :math:a to learn, there is only two
values are legitimate: 1, or the number of channels at input. Default: 1
init: the initial value of :math:a. Default: 0.25

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-1.2, -3.7, 2.7]).astype(np.float32))
>>> prelu = M.PReLU()
>>> output = prelu(data)
>>> output.numpy()
array([-0.3  , -0.925,  2.7  ], dtype=float32)
"""

def __init__(self, num_parameters: int = 1, init: float = 0.25, **kwargs):
super().__init__(**kwargs)
self.num_parameters = num_parameters
if num_parameters > 1:
# Assume format is NCHW
self.weight = Parameter(
data=np.full((1, num_parameters, 1, 1), init, dtype=np.float32)
)
else:
self.weight = Parameter(data=[init])

def forward(self, inputs):
return prelu(inputs, self.weight)

[文档]class LeakyReLU(Module):
r"""Applies the element-wise function:

.. math::
\text{LeakyReLU}(x) = \max(0,x) + negative\_slope \times \min(0,x)

or

.. math::
\text{LeakyReLU}(x) =
\begin{cases}
x, & \text{ if } x \geq 0 \\
negative\_slope \times x, & \text{ otherwise }
\end{cases}

Examples:
>>> import numpy as np
>>> data = mge.tensor(np.array([-8, -12, 6, 10]).astype(np.float32))
>>> leakyrelu = M.LeakyReLU(0.01)
>>> output = leakyrelu(data)
>>> output.numpy()
array([-0.08, -0.12,  6.  , 10.  ], dtype=float32)
"""

def __init__(self, negative_slope: float = 0.01, **kwargs):
super().__init__(**kwargs)
self.negative_slope = negative_slope

def forward(self, inputs):
return leaky_relu(inputs, self.negative_slope)