Source code for torch.nn.modules.activation

import warnings
from typing import Optional, Tuple

import torch
from torch import Tensor
from .linear import NonDynamicallyQuantizableLinear
from torch.nn.init import constant_, xavier_normal_, xavier_uniform_
from torch.nn.parameter import Parameter
from .module import Module
from .. import functional as F

__all__ = ['Threshold', 'ReLU', 'RReLU', 'Hardtanh', 'ReLU6', 'Sigmoid', 'Hardsigmoid', 'Tanh',
           'SiLU', 'Mish', 'Hardswish', 'ELU', 'CELU', 'SELU', 'GLU', 'GELU', 'Hardshrink', 'LeakyReLU',
           'LogSigmoid', 'Softplus', 'Softshrink', 'MultiheadAttention', 'PReLU', 'Softsign', 'Tanhshrink',
           'Softmin', 'Softmax', 'Softmax2d', 'LogSoftmax']

class Threshold(Module):
    r"""Thresholds each element of the input Tensor.

    Threshold is defined as:

    .. math::
        y =
        \begin{cases}
        x, &\text{ if } x > \text{threshold} \\
        \text{value}, &\text{ otherwise }
        \end{cases}

    Args:
        threshold: The value to threshold at
        value: The value to replace with
        inplace: can optionally do the operation in-place. Default: ``False``

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

    Examples::

        >>> m = nn.Threshold(0.1, 20)
        >>> input = torch.randn(2)
        >>> output = m(input)
    """
    __constants__ = ['threshold', 'value', 'inplace']

    threshold: float
    value: float
    inplace: bool

    def __init__(self, threshold: float, value: float, inplace: bool = False) -> None:
        super(Threshold, self).__init__()
        self.threshold = threshold
        self.value = value
        self.inplace = inplace
        # TODO: check in THNN (if inplace == True, then assert value <= threshold)

    def forward(self, input: Tensor) -> Tensor:
        return F.threshold(input, self.threshold, self.value, self.inplace)

    def extra_repr(self):
        inplace_str = ', inplace=True' if self.inplace else ''
        return 'threshold={}, value={}{}'.format(
            self.threshold, self.value, inplace_str
        )


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

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

    Args:
        inplace: can optionally do the operation in-place. Default: ``False``

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

    .. image:: ../scripts/activation_images/ReLU.png

    Examples::

        >>> m = nn.ReLU()
        >>> input = torch.randn(2)
        >>> output = m(input)


      An implementation of CReLU - https://arxiv.org/abs/1603.05201

        >>> m = nn.ReLU()
        >>> input = torch.randn(2).unsqueeze(0)
        >>> output = torch.cat((m(input),m(-input)))
    """
    __constants__ = ['inplace']
    inplace: bool

[docs] def __init__(self, inplace: bool = False): super(ReLU, self).__init__() self.inplace = inplace
[docs] def forward(self, input: Tensor) -> Tensor: return F.relu(input, inplace=self.inplace)
[docs] def extra_repr(self) -> str: inplace_str = 'inplace=True' if self.inplace else '' return inplace_str
class RReLU(Module): r"""Applies the randomized leaky rectified liner unit function, element-wise, as described in the paper: `Empirical Evaluation of Rectified Activations in Convolutional Network`_. The function is defined as: .. math:: \text{RReLU}(x) = \begin{cases} x & \text{if } x \geq 0 \\ ax & \text{ otherwise } \end{cases} where :math:`a` is randomly sampled from uniform distribution :math:`\mathcal{U}(\text{lower}, \text{upper})`. See: https://arxiv.org/pdf/1505.00853.pdf Args: lower: lower bound of the uniform distribution. Default: :math:`\frac{1}{8}` upper: upper bound of the uniform distribution. Default: :math:`\frac{1}{3}` inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/RReLU.png Examples:: >>> m = nn.RReLU(0.1, 0.3) >>> input = torch.randn(2) >>> output = m(input) .. _`Empirical Evaluation of Rectified Activations in Convolutional Network`: https://arxiv.org/abs/1505.00853 """ __constants__ = ['lower', 'upper', 'inplace'] lower: float upper: float inplace: bool def __init__( self, lower: float = 1. / 8, upper: float = 1. / 3, inplace: bool = False ): super(RReLU, self).__init__() self.lower = lower self.upper = upper self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.rrelu(input, self.lower, self.upper, self.training, self.inplace) def extra_repr(self): inplace_str = ', inplace=True' if self.inplace else '' return 'lower={}, upper={}{}'.format(self.lower, self.upper, inplace_str) class Hardtanh(Module): r"""Applies the HardTanh function element-wise. HardTanh is defined as: .. math:: \text{HardTanh}(x) = \begin{cases} \text{max\_val} & \text{ if } x > \text{ max\_val } \\ \text{min\_val} & \text{ if } x < \text{ min\_val } \\ x & \text{ otherwise } \\ \end{cases} Args: min_val: minimum value of the linear region range. Default: -1 max_val: maximum value of the linear region range. Default: 1 inplace: can optionally do the operation in-place. Default: ``False`` Keyword arguments :attr:`min_value` and :attr:`max_value` have been deprecated in favor of :attr:`min_val` and :attr:`max_val`. Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Hardtanh.png Examples:: >>> m = nn.Hardtanh(-2, 2) >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['min_val', 'max_val', 'inplace'] min_val: float max_val: float inplace: bool def __init__( self, min_val: float = -1., max_val: float = 1., inplace: bool = False, min_value: Optional[float] = None, max_value: Optional[float] = None ) -> None: super(Hardtanh, self).__init__() if min_value is not None: warnings.warn("keyword argument min_value is deprecated and rename to min_val") min_val = min_value if max_value is not None: warnings.warn("keyword argument max_value is deprecated and rename to max_val") max_val = max_value self.min_val = min_val self.max_val = max_val self.inplace = inplace assert self.max_val > self.min_val def forward(self, input: Tensor) -> Tensor: return F.hardtanh(input, self.min_val, self.max_val, self.inplace) def extra_repr(self) -> str: inplace_str = ', inplace=True' if self.inplace else '' return 'min_val={}, max_val={}{}'.format( self.min_val, self.max_val, inplace_str ) class ReLU6(Hardtanh): r"""Applies the element-wise function: .. math:: \text{ReLU6}(x) = \min(\max(0,x), 6) Args: inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/ReLU6.png Examples:: >>> m = nn.ReLU6() >>> input = torch.randn(2) >>> output = m(input) """ def __init__(self, inplace: bool = False): super(ReLU6, self).__init__(0., 6., inplace) def extra_repr(self) -> str: inplace_str = 'inplace=True' if self.inplace else '' return inplace_str class Sigmoid(Module): r"""Applies the element-wise function: .. math:: \text{Sigmoid}(x) = \sigma(x) = \frac{1}{1 + \exp(-x)} Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Sigmoid.png Examples:: >>> m = nn.Sigmoid() >>> input = torch.randn(2) >>> output = m(input) """
[docs] def forward(self, input: Tensor) -> Tensor: return torch.sigmoid(input)
class Hardsigmoid(Module): r"""Applies the Hardsigmoid function element-wise. Hardsigmoid is defined as: .. math:: \text{Hardsigmoid}(x) = \begin{cases} 0 & \text{if~} x \le -3, \\ 1 & \text{if~} x \ge +3, \\ x / 6 + 1 / 2 & \text{otherwise} \end{cases} Args: inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Hardsigmoid.png Examples:: >>> m = nn.Hardsigmoid() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['inplace'] inplace: bool def __init__(self, inplace : bool = False) -> None: super(Hardsigmoid, self).__init__() self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.hardsigmoid(input, self.inplace) class Tanh(Module): r"""Applies the Hyperbolic Tangent (Tanh) function element-wise. Tanh is defined as: .. math:: \text{Tanh}(x) = \tanh(x) = \frac{\exp(x) - \exp(-x)} {\exp(x) + \exp(-x)} Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Tanh.png Examples:: >>> m = nn.Tanh() >>> input = torch.randn(2) >>> output = m(input) """ def forward(self, input: Tensor) -> Tensor: return torch.tanh(input) class SiLU(Module): r"""Applies the Sigmoid Linear Unit (SiLU) function, element-wise. The SiLU function is also known as the swish function. .. math:: \text{silu}(x) = x * \sigma(x), \text{where } \sigma(x) \text{ is the logistic sigmoid.} .. note:: See `Gaussian Error Linear Units (GELUs) <https://arxiv.org/abs/1606.08415>`_ where the SiLU (Sigmoid Linear Unit) was originally coined, and see `Sigmoid-Weighted Linear Units for Neural Network Function Approximation in Reinforcement Learning <https://arxiv.org/abs/1702.03118>`_ and `Swish: a Self-Gated Activation Function <https://arxiv.org/abs/1710.05941v1>`_ where the SiLU was experimented with later. Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/SiLU.png Examples:: >>> m = nn.SiLU() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['inplace'] inplace: bool def __init__(self, inplace: bool = False): super(SiLU, self).__init__() self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.silu(input, inplace=self.inplace) def extra_repr(self) -> str: inplace_str = 'inplace=True' if self.inplace else '' return inplace_str class Mish(Module): r"""Applies the Mish function, element-wise. Mish: A Self Regularized Non-Monotonic Neural Activation Function. .. math:: \text{Mish}(x) = x * \text{Tanh}(\text{Softplus}(x)) .. note:: See `Mish: A Self Regularized Non-Monotonic Neural Activation Function <https://arxiv.org/abs/1908.08681>`_ Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Mish.png Examples:: >>> m = nn.Mish() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['inplace'] inplace: bool def __init__(self, inplace: bool = False): super(Mish, self).__init__() self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.mish(input, inplace=self.inplace) def extra_repr(self) -> str: inplace_str = 'inplace=True' if self.inplace else '' return inplace_str class Hardswish(Module): r"""Applies the Hardswish function, element-wise, as described in the paper: `Searching for MobileNetV3 <https://arxiv.org/abs/1905.02244>`_. Hardswish is defined as: .. math:: \text{Hardswish}(x) = \begin{cases} 0 & \text{if~} x \le -3, \\ x & \text{if~} x \ge +3, \\ x \cdot (x + 3) /6 & \text{otherwise} \end{cases} Args: inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Hardswish.png Examples:: >>> m = nn.Hardswish() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['inplace'] inplace: bool def __init__(self, inplace : bool = False) -> None: super(Hardswish, self).__init__() self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.hardswish(input, self.inplace) class ELU(Module): r"""Applies the Exponential Linear Unit (ELU) function, element-wise, as described in the paper: `Fast and Accurate Deep Network Learning by Exponential Linear Units (ELUs) <https://arxiv.org/abs/1511.07289>`__. ELU is defined as: .. math:: \text{ELU}(x) = \begin{cases} x, & \text{ if } x > 0\\ \alpha * (\exp(x) - 1), & \text{ if } x \leq 0 \end{cases} Args: alpha: the :math:`\alpha` value for the ELU formulation. Default: 1.0 inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/ELU.png Examples:: >>> m = nn.ELU() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['alpha', 'inplace'] alpha: float inplace: bool def __init__(self, alpha: float = 1., inplace: bool = False) -> None: super(ELU, self).__init__() self.alpha = alpha self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.elu(input, self.alpha, self.inplace) def extra_repr(self) -> str: inplace_str = ', inplace=True' if self.inplace else '' return 'alpha={}{}'.format(self.alpha, inplace_str) class CELU(Module): r"""Applies the element-wise function: .. math:: \text{CELU}(x) = \max(0,x) + \min(0, \alpha * (\exp(x/\alpha) - 1)) More details can be found in the paper `Continuously Differentiable Exponential Linear Units`_ . Args: alpha: the :math:`\alpha` value for the CELU formulation. Default: 1.0 inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/CELU.png Examples:: >>> m = nn.CELU() >>> input = torch.randn(2) >>> output = m(input) .. _`Continuously Differentiable Exponential Linear Units`: https://arxiv.org/abs/1704.07483 """ __constants__ = ['alpha', 'inplace'] alpha: float inplace: bool def __init__(self, alpha: float = 1., inplace: bool = False) -> None: super(CELU, self).__init__() self.alpha = alpha self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.celu(input, self.alpha, self.inplace) def extra_repr(self) -> str: inplace_str = ', inplace=True' if self.inplace else '' return 'alpha={}{}'.format(self.alpha, inplace_str) class SELU(Module): r"""Applied element-wise, as: .. math:: \text{SELU}(x) = \text{scale} * (\max(0,x) + \min(0, \alpha * (\exp(x) - 1))) with :math:`\alpha = 1.6732632423543772848170429916717` and :math:`\text{scale} = 1.0507009873554804934193349852946`. .. warning:: When using ``kaiming_normal`` or ``kaiming_normal_`` for initialisation, ``nonlinearity='linear'`` should be used instead of ``nonlinearity='selu'`` in order to get `Self-Normalizing Neural Networks`_. See :func:`torch.nn.init.calculate_gain` for more information. More details can be found in the paper `Self-Normalizing Neural Networks`_ . Args: inplace (bool, optional): can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/SELU.png Examples:: >>> m = nn.SELU() >>> input = torch.randn(2) >>> output = m(input) .. _Self-Normalizing Neural Networks: https://arxiv.org/abs/1706.02515 """ __constants__ = ['inplace'] inplace: bool def __init__(self, inplace: bool = False) -> None: super(SELU, self).__init__() self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.selu(input, self.inplace) def extra_repr(self) -> str: inplace_str = 'inplace=True' if self.inplace else '' return inplace_str class GLU(Module): r"""Applies the gated linear unit function :math:`{GLU}(a, b)= a \otimes \sigma(b)` where :math:`a` is the first half of the input matrices and :math:`b` is the second half. Args: dim (int): the dimension on which to split the input. Default: -1 Shape: - Input: :math:`(\ast_1, N, \ast_2)` where `*` means, any number of additional dimensions - Output: :math:`(\ast_1, M, \ast_2)` where :math:`M=N/2` Examples:: >>> m = nn.GLU() >>> input = torch.randn(4, 2) >>> output = m(input) """ __constants__ = ['dim'] dim: int def __init__(self, dim: int = -1) -> None: super(GLU, self).__init__() self.dim = dim def forward(self, input: Tensor) -> Tensor: return F.glu(input, self.dim) def extra_repr(self) -> str: return 'dim={}'.format(self.dim) class GELU(Module): r"""Applies the Gaussian Error Linear Units function: .. math:: \text{GELU}(x) = x * \Phi(x) where :math:`\Phi(x)` is the Cumulative Distribution Function for Gaussian Distribution. When the approximate argument is 'tanh', Gelu is estimated with: .. math:: \text{GELU}(x) = 0.5 * x * (1 + \text{Tanh}(\sqrt(2 / \pi) * (x + 0.044715 * x^3))) Args: approximate (str, optional): the gelu approximation algorithm to use: ``'none'`` | ``'tanh'``. Default: ``'none'`` Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/GELU.png Examples:: >>> m = nn.GELU() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['approximate'] approximate: str
[docs] def __init__(self, approximate: str = 'none') -> None: super(GELU, self).__init__() self.approximate = approximate
[docs] def forward(self, input: Tensor) -> Tensor: return F.gelu(input, approximate=self.approximate)
[docs] def extra_repr(self) -> str: return 'approximate={}'.format(repr(self.approximate))
class Hardshrink(Module): r"""Applies the Hard Shrinkage (Hardshrink) function element-wise. Hardshrink is defined as: .. math:: \text{HardShrink}(x) = \begin{cases} x, & \text{ if } x > \lambda \\ x, & \text{ if } x < -\lambda \\ 0, & \text{ otherwise } \end{cases} Args: lambd: the :math:`\lambda` value for the Hardshrink formulation. Default: 0.5 Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Hardshrink.png Examples:: >>> m = nn.Hardshrink() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['lambd'] lambd: float def __init__(self, lambd: float = 0.5) -> None: super(Hardshrink, self).__init__() self.lambd = lambd def forward(self, input: Tensor) -> Tensor: return F.hardshrink(input, self.lambd) def extra_repr(self) -> str: return '{}'.format(self.lambd) class LeakyReLU(Module): r"""Applies the element-wise function: .. math:: \text{LeakyReLU}(x) = \max(0, x) + \text{negative\_slope} * \min(0, x) or .. math:: \text{LeakyReLU}(x) = \begin{cases} x, & \text{ if } x \geq 0 \\ \text{negative\_slope} \times x, & \text{ otherwise } \end{cases} Args: negative_slope: Controls the angle of the negative slope. Default: 1e-2 inplace: can optionally do the operation in-place. Default: ``False`` Shape: - Input: :math:`(*)` where `*` means, any number of additional dimensions - Output: :math:`(*)`, same shape as the input .. image:: ../scripts/activation_images/LeakyReLU.png Examples:: >>> m = nn.LeakyReLU(0.1) >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['inplace', 'negative_slope'] inplace: bool negative_slope: float def __init__(self, negative_slope: float = 1e-2, inplace: bool = False) -> None: super(LeakyReLU, self).__init__() self.negative_slope = negative_slope self.inplace = inplace def forward(self, input: Tensor) -> Tensor: return F.leaky_relu(input, self.negative_slope, self.inplace) def extra_repr(self) -> str: inplace_str = ', inplace=True' if self.inplace else '' return 'negative_slope={}{}'.format(self.negative_slope, inplace_str) class LogSigmoid(Module): r"""Applies the element-wise function: .. math:: \text{LogSigmoid}(x) = \log\left(\frac{ 1 }{ 1 + \exp(-x)}\right) Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/LogSigmoid.png Examples:: >>> m = nn.LogSigmoid() >>> input = torch.randn(2) >>> output = m(input) """ def forward(self, input: Tensor) -> Tensor: return F.logsigmoid(input) class Softplus(Module): r"""Applies the Softplus function :math:`\text{Softplus}(x) = \frac{1}{\beta} * \log(1 + \exp(\beta * x))` element-wise. SoftPlus is a smooth approximation to the ReLU function and can be used to constrain the output of a machine to always be positive. For numerical stability the implementation reverts to the linear function when :math:`input \times \beta > threshold`. Args: beta: the :math:`\beta` value for the Softplus formulation. Default: 1 threshold: values above this revert to a linear function. Default: 20 Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Softplus.png Examples:: >>> m = nn.Softplus() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['beta', 'threshold'] beta: int threshold: int def __init__(self, beta: int = 1, threshold: int = 20) -> None: super(Softplus, self).__init__() self.beta = beta self.threshold = threshold def forward(self, input: Tensor) -> Tensor: return F.softplus(input, self.beta, self.threshold) def extra_repr(self) -> str: return 'beta={}, threshold={}'.format(self.beta, self.threshold) class Softshrink(Module): r"""Applies the soft shrinkage function elementwise: .. math:: \text{SoftShrinkage}(x) = \begin{cases} x - \lambda, & \text{ if } x > \lambda \\ x + \lambda, & \text{ if } x < -\lambda \\ 0, & \text{ otherwise } \end{cases} Args: lambd: the :math:`\lambda` (must be no less than zero) value for the Softshrink formulation. Default: 0.5 Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Softshrink.png Examples:: >>> m = nn.Softshrink() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['lambd'] lambd: float def __init__(self, lambd: float = 0.5) -> None: super(Softshrink, self).__init__() self.lambd = lambd def forward(self, input: Tensor) -> Tensor: return F.softshrink(input, self.lambd) def extra_repr(self) -> str: return str(self.lambd) class MultiheadAttention(Module): r"""Allows the model to jointly attend to information from different representation subspaces as described in the paper: `Attention Is All You Need <https://arxiv.org/abs/1706.03762>`_. Multi-Head Attention is defined as: .. math:: \text{MultiHead}(Q, K, V) = \text{Concat}(head_1,\dots,head_h)W^O where :math:`head_i = \text{Attention}(QW_i^Q, KW_i^K, VW_i^V)`. ``forward()`` will use a special optimized implementation if all of the following conditions are met: - self attention is being computed (i.e., ``query``, ``key``, and ``value`` are the same tensor. This restriction will be loosened in the future.) - Either autograd is disabled (using ``torch.inference_mode`` or ``torch.no_grad``) or no tensor argument ``requires_grad`` - training is disabled (using ``.eval()``) - dropout is 0 - ``add_bias_kv`` is ``False`` - ``add_zero_attn`` is ``False`` - ``batch_first`` is ``True`` and the input is batched - ``kdim`` and ``vdim`` are equal to ``embed_dim`` - at most one of ``key_padding_mask`` or ``attn_mask`` is passed - if a `NestedTensor <https://pytorch.org/docs/stable/nested.html>`_ is passed, neither ``key_padding_mask`` nor ``attn_mask`` is passed If the optimized implementation is in use, a `NestedTensor <https://pytorch.org/docs/stable/nested.html>`_ can be passed for ``query``/``key``/``value`` to represent padding more efficiently than using a padding mask. In this case, a `NestedTensor <https://pytorch.org/docs/stable/nested.html>`_ will be returned, and an additional speedup proportional to the fraction of the input that is padding can be expected. Args: embed_dim: Total dimension of the model. num_heads: Number of parallel attention heads. Note that ``embed_dim`` will be split across ``num_heads`` (i.e. each head will have dimension ``embed_dim // num_heads``). dropout: Dropout probability on ``attn_output_weights``. Default: ``0.0`` (no dropout). bias: If specified, adds bias to input / output projection layers. Default: ``True``. add_bias_kv: If specified, adds bias to the key and value sequences at dim=0. Default: ``False``. add_zero_attn: If specified, adds a new batch of zeros to the key and value sequences at dim=1. Default: ``False``. kdim: Total number of features for keys. Default: ``None`` (uses ``kdim=embed_dim``). vdim: Total number of features for values. Default: ``None`` (uses ``vdim=embed_dim``). batch_first: If ``True``, then the input and output tensors are provided as (batch, seq, feature). Default: ``False`` (seq, batch, feature). Examples:: >>> # xdoctest: +SKIP >>> multihead_attn = nn.MultiheadAttention(embed_dim, num_heads) >>> attn_output, attn_output_weights = multihead_attn(query, key, value) """ __constants__ = ['batch_first'] bias_k: Optional[torch.Tensor] bias_v: Optional[torch.Tensor] def __init__(self, embed_dim, num_heads, dropout=0., bias=True, add_bias_kv=False, add_zero_attn=False, kdim=None, vdim=None, batch_first=False, device=None, dtype=None) -> None: factory_kwargs = {'device': device, 'dtype': dtype} super(MultiheadAttention, self).__init__() self.embed_dim = embed_dim self.kdim = kdim if kdim is not None else embed_dim self.vdim = vdim if vdim is not None else embed_dim self._qkv_same_embed_dim = self.kdim == embed_dim and self.vdim == embed_dim self.num_heads = num_heads self.dropout = dropout self.batch_first = batch_first self.head_dim = embed_dim // num_heads assert self.head_dim * num_heads == self.embed_dim, "embed_dim must be divisible by num_heads" if not self._qkv_same_embed_dim: self.q_proj_weight = Parameter(torch.empty((embed_dim, embed_dim), **factory_kwargs)) self.k_proj_weight = Parameter(torch.empty((embed_dim, self.kdim), **factory_kwargs)) self.v_proj_weight = Parameter(torch.empty((embed_dim, self.vdim), **factory_kwargs)) self.register_parameter('in_proj_weight', None) else: self.in_proj_weight = Parameter(torch.empty((3 * embed_dim, embed_dim), **factory_kwargs)) self.register_parameter('q_proj_weight', None) self.register_parameter('k_proj_weight', None) self.register_parameter('v_proj_weight', None) if bias: self.in_proj_bias = Parameter(torch.empty(3 * embed_dim, **factory_kwargs)) else: self.register_parameter('in_proj_bias', None) self.out_proj = NonDynamicallyQuantizableLinear(embed_dim, embed_dim, bias=bias, **factory_kwargs) if add_bias_kv: self.bias_k = Parameter(torch.empty((1, 1, embed_dim), **factory_kwargs)) self.bias_v = Parameter(torch.empty((1, 1, embed_dim), **factory_kwargs)) else: self.bias_k = self.bias_v = None self.add_zero_attn = add_zero_attn self._reset_parameters() def _reset_parameters(self): if self._qkv_same_embed_dim: xavier_uniform_(self.in_proj_weight) else: xavier_uniform_(self.q_proj_weight) xavier_uniform_(self.k_proj_weight) xavier_uniform_(self.v_proj_weight) if self.in_proj_bias is not None: constant_(self.in_proj_bias, 0.) constant_(self.out_proj.bias, 0.) if self.bias_k is not None: xavier_normal_(self.bias_k) if self.bias_v is not None: xavier_normal_(self.bias_v) def __setstate__(self, state): # Support loading old MultiheadAttention checkpoints generated by v1.1.0 if '_qkv_same_embed_dim' not in state: state['_qkv_same_embed_dim'] = True super(MultiheadAttention, self).__setstate__(state) def forward(self, query: Tensor, key: Tensor, value: Tensor, key_padding_mask: Optional[Tensor] = None, need_weights: bool = True, attn_mask: Optional[Tensor] = None, average_attn_weights: bool = True) -> Tuple[Tensor, Optional[Tensor]]: r""" Args: query: Query embeddings of shape :math:`(L, E_q)` for unbatched input, :math:`(L, N, E_q)` when ``batch_first=False`` or :math:`(N, L, E_q)` when ``batch_first=True``, where :math:`L` is the target sequence length, :math:`N` is the batch size, and :math:`E_q` is the query embedding dimension ``embed_dim``. Queries are compared against key-value pairs to produce the output. See "Attention Is All You Need" for more details. key: Key embeddings of shape :math:`(S, E_k)` for unbatched input, :math:`(S, N, E_k)` when ``batch_first=False`` or :math:`(N, S, E_k)` when ``batch_first=True``, where :math:`S` is the source sequence length, :math:`N` is the batch size, and :math:`E_k` is the key embedding dimension ``kdim``. See "Attention Is All You Need" for more details. value: Value embeddings of shape :math:`(S, E_v)` for unbatched input, :math:`(S, N, E_v)` when ``batch_first=False`` or :math:`(N, S, E_v)` when ``batch_first=True``, where :math:`S` is the source sequence length, :math:`N` is the batch size, and :math:`E_v` is the value embedding dimension ``vdim``. See "Attention Is All You Need" for more details. key_padding_mask: If specified, a mask of shape :math:`(N, S)` indicating which elements within ``key`` to ignore for the purpose of attention (i.e. treat as "padding"). For unbatched `query`, shape should be :math:`(S)`. Binary and byte masks are supported. For a binary mask, a ``True`` value indicates that the corresponding ``key`` value will be ignored for the purpose of attention. For a float mask, it will be directly added to the corresponding ``key`` value. need_weights: If specified, returns ``attn_output_weights`` in addition to ``attn_outputs``. Default: ``True``. attn_mask: If specified, a 2D or 3D mask preventing attention to certain positions. Must be of shape :math:`(L, S)` or :math:`(N\cdot\text{num\_heads}, L, S)`, where :math:`N` is the batch size, :math:`L` is the target sequence length, and :math:`S` is the source sequence length. A 2D mask will be broadcasted across the batch while a 3D mask allows for a different mask for each entry in the batch. Binary, byte, and float masks are supported. For a binary mask, a ``True`` value indicates that the corresponding position is not allowed to attend. For a byte mask, a non-zero value indicates that the corresponding position is not allowed to attend. For a float mask, the mask values will be added to the attention weight. average_attn_weights: If true, indicates that the returned ``attn_weights`` should be averaged across heads. Otherwise, ``attn_weights`` are provided separately per head. Note that this flag only has an effect when ``need_weights=True``. Default: ``True`` (i.e. average weights across heads) Outputs: - **attn_output** - Attention outputs of shape :math:`(L, E)` when input is unbatched, :math:`(L, N, E)` when ``batch_first=False`` or :math:`(N, L, E)` when ``batch_first=True``, where :math:`L` is the target sequence length, :math:`N` is the batch size, and :math:`E` is the embedding dimension ``embed_dim``. - **attn_output_weights** - Only returned when ``need_weights=True``. If ``average_attn_weights=True``, returns attention weights averaged across heads of shape :math:`(L, S)` when input is unbatched or :math:`(N, L, S)`, where :math:`N` is the batch size, :math:`L` is the target sequence length, and :math:`S` is the source sequence length. If ``average_attn_weights=False``, returns attention weights per head of shape :math:`(\text{num\_heads}, L, S)` when input is unbatched or :math:`(N, \text{num\_heads}, L, S)`. .. note:: `batch_first` argument is ignored for unbatched inputs. """ is_batched = query.dim() == 3 if key_padding_mask is not None: _kpm_dtype = key_padding_mask.dtype if _kpm_dtype != torch.bool and not torch.is_floating_point(key_padding_mask): raise AssertionError( "only bool and floating types of key_padding_mask are supported") why_not_fast_path = '' if not is_batched: why_not_fast_path = f"input not batched; expected query.dim() of 3 but got {query.dim()}" elif query is not key or key is not value: # When lifting this restriction, don't forget to either # enforce that the dtypes all match or test cases where # they don't! why_not_fast_path = "non-self attention was used (query, key, and value are not the same Tensor)" elif self.in_proj_bias is not None and query.dtype != self.in_proj_bias.dtype: why_not_fast_path = f"dtypes of query ({query.dtype}) and self.in_proj_bias ({self.in_proj_bias.dtype}) don't match" elif self.in_proj_weight is not None and query.dtype != self.in_proj_weight.dtype: # this case will fail anyway, but at least they'll get a useful error message. why_not_fast_path = f"dtypes of query ({query.dtype}) and self.in_proj_weight ({self.in_proj_weight.dtype}) don't match" elif self.training: why_not_fast_path = "training is enabled" elif not self.batch_first: why_not_fast_path = "batch_first was not True" elif self.bias_k is not None: why_not_fast_path = "self.bias_k was not None" elif self.bias_v is not None: why_not_fast_path = "self.bias_v was not None" elif self.dropout: why_not_fast_path = f"dropout was {self.dropout}, required zero" elif self.add_zero_attn: why_not_fast_path = "add_zero_attn was enabled" elif not self._qkv_same_embed_dim: why_not_fast_path = "_qkv_same_embed_dim was not True" elif attn_mask is not None: why_not_fast_path = "attn_mask was not None" elif query.is_nested and key_padding_mask is not None: why_not_fast_path = "key_padding_mask is not supported with NestedTensor input" elif self.num_heads % 2 == 1: why_not_fast_path = "num_heads is odd" elif torch.is_autocast_enabled(): why_not_fast_path = "autocast is enabled" if not why_not_fast_path: tensor_args = ( query, key, value, self.in_proj_weight, self.in_proj_bias, self.out_proj.weight, self.out_proj.bias, ) # We have to use list comprehensions below because TorchScript does not support # generator expressions. if torch.overrides.has_torch_function(tensor_args): why_not_fast_path = "some Tensor argument has_torch_function" elif not all([(x.is_cuda or 'cpu' in str(x.device)) for x in tensor_args]): why_not_fast_path = "some Tensor argument is neither CUDA nor CPU" elif torch.is_grad_enabled() and any([x.requires_grad for x in tensor_args]): why_not_fast_path = ("grad is enabled and at least one of query or the " "input/output projection weights or biases requires_grad") if not why_not_fast_path: return torch._native_multi_head_attention( query, key, value, self.embed_dim, self.num_heads, self.in_proj_weight, self.in_proj_bias, self.out_proj.weight, self.out_proj.bias, key_padding_mask if key_padding_mask is not None else attn_mask, need_weights, average_attn_weights, 1 if key_padding_mask is not None else 0 if attn_mask is not None else None) any_nested = query.is_nested or key.is_nested or value.is_nested assert not any_nested, ("MultiheadAttention does not support NestedTensor outside of its fast path. " + f"The fast path was not hit because {why_not_fast_path}") if self.batch_first and is_batched: # make sure that the transpose op does not affect the "is" property if key is value: if query is key: query = key = value = query.transpose(1, 0) else: query, key = [x.transpose(1, 0) for x in (query, key)] value = key else: query, key, value = [x.transpose(1, 0) for x in (query, key, value)] if not self._qkv_same_embed_dim: attn_output, attn_output_weights = F.multi_head_attention_forward( query, key, value, self.embed_dim, self.num_heads, self.in_proj_weight, self.in_proj_bias, self.bias_k, self.bias_v, self.add_zero_attn, self.dropout, self.out_proj.weight, self.out_proj.bias, training=self.training, key_padding_mask=key_padding_mask, need_weights=need_weights, attn_mask=attn_mask, use_separate_proj_weight=True, q_proj_weight=self.q_proj_weight, k_proj_weight=self.k_proj_weight, v_proj_weight=self.v_proj_weight, average_attn_weights=average_attn_weights) else: attn_output, attn_output_weights = F.multi_head_attention_forward( query, key, value, self.embed_dim, self.num_heads, self.in_proj_weight, self.in_proj_bias, self.bias_k, self.bias_v, self.add_zero_attn, self.dropout, self.out_proj.weight, self.out_proj.bias, training=self.training, key_padding_mask=key_padding_mask, need_weights=need_weights, attn_mask=attn_mask, average_attn_weights=average_attn_weights) if self.batch_first and is_batched: return attn_output.transpose(1, 0), attn_output_weights else: return attn_output, attn_output_weights 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, `nn.PReLU()` uses a single parameter :math:`a` across all input channels. If called with `nn.PReLU(nChannels)`, a separate :math:`a` is used for each input channel. .. note:: weight decay should not be used when learning :math:`a` for good performance. .. note:: Channel dim is the 2nd dim of input. When input has dims < 2, then there is no channel dim and the number of channels = 1. Args: num_parameters (int): number of :math:`a` to learn. Although it takes an int as input, there is only two values are legitimate: 1, or the number of channels at input. Default: 1 init (float): the initial value of :math:`a`. Default: 0.25 Shape: - Input: :math:`( *)` where `*` means, any number of additional dimensions. - Output: :math:`(*)`, same shape as the input. Attributes: weight (Tensor): the learnable weights of shape (:attr:`num_parameters`). .. image:: ../scripts/activation_images/PReLU.png Examples:: >>> m = nn.PReLU() >>> input = torch.randn(2) >>> output = m(input) """ __constants__ = ['num_parameters'] num_parameters: int def __init__(self, num_parameters: int = 1, init: float = 0.25, device=None, dtype=None) -> None: factory_kwargs = {'device': device, 'dtype': dtype} self.num_parameters = num_parameters super(PReLU, self).__init__() self.weight = Parameter(torch.empty(num_parameters, **factory_kwargs).fill_(init)) def forward(self, input: Tensor) -> Tensor: return F.prelu(input, self.weight)
[docs] def extra_repr(self) -> str: return 'num_parameters={}'.format(self.num_parameters)
class Softsign(Module): r"""Applies the element-wise function: .. math:: \text{SoftSign}(x) = \frac{x}{ 1 + |x|} Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Softsign.png Examples:: >>> m = nn.Softsign() >>> input = torch.randn(2) >>> output = m(input) """ def forward(self, input: Tensor) -> Tensor: return F.softsign(input) class Tanhshrink(Module): r"""Applies the element-wise function: .. math:: \text{Tanhshrink}(x) = x - \tanh(x) Shape: - Input: :math:`(*)`, where :math:`*` means any number of dimensions. - Output: :math:`(*)`, same shape as the input. .. image:: ../scripts/activation_images/Tanhshrink.png Examples:: >>> m = nn.Tanhshrink() >>> input = torch.randn(2) >>> output = m(input) """ def forward(self, input: Tensor) -> Tensor: return F.tanhshrink(input) class Softmin(Module): r"""Applies the Softmin function to an n-dimensional input Tensor rescaling them so that the elements of the n-dimensional output Tensor lie in the range `[0, 1]` and sum to 1. Softmin is defined as: .. math:: \text{Softmin}(x_{i}) = \frac{\exp(-x_i)}{\sum_j \exp(-x_j)} Shape: - Input: :math:`(*)` where `*` means, any number of additional dimensions - Output: :math:`(*)`, same shape as the input Args: dim (int): A dimension along which Softmin will be computed (so every slice along dim will sum to 1). Returns: a Tensor of the same dimension and shape as the input, with values in the range [0, 1] Examples:: >>> m = nn.Softmin(dim=1) >>> input = torch.randn(2, 3) >>> output = m(input) """ __constants__ = ['dim'] dim: Optional[int] def __init__(self, dim: Optional[int] = None) -> None: super(Softmin, self).__init__() self.dim = dim def __setstate__(self, state): super().__setstate__(state) if not hasattr(self, 'dim'): self.dim = None def forward(self, input: Tensor) -> Tensor: return F.softmin(input, self.dim, _stacklevel=5) def extra_repr(self): return 'dim={dim}'.format(dim=self.dim) class Softmax(Module): r"""Applies the Softmax function to an n-dimensional input Tensor rescaling them so that the elements of the n-dimensional output Tensor lie in the range [0,1] and sum to 1. Softmax is defined as: .. math:: \text{Softmax}(x_{i}) = \frac{\exp(x_i)}{\sum_j \exp(x_j)} When the input Tensor is a sparse tensor then the unspecifed values are treated as ``-inf``. Shape: - Input: :math:`(*)` where `*` means, any number of additional dimensions - Output: :math:`(*)`, same shape as the input Returns: a Tensor of the same dimension and shape as the input with values in the range [0, 1] Args: dim (int): A dimension along which Softmax will be computed (so every slice along dim will sum to 1). .. note:: This module doesn't work directly with NLLLoss, which expects the Log to be computed between the Softmax and itself. Use `LogSoftmax` instead (it's faster and has better numerical properties). Examples:: >>> m = nn.Softmax(dim=1) >>> input = torch.randn(2, 3) >>> output = m(input) """ __constants__ = ['dim'] dim: Optional[int]
[docs] def __init__(self, dim: Optional[int] = None) -> None: super(Softmax, self).__init__() self.dim = dim
def __setstate__(self, state): super().__setstate__(state) if not hasattr(self, 'dim'): self.dim = None
[docs] def forward(self, input: Tensor) -> Tensor: return F.softmax(input, self.dim, _stacklevel=5)
[docs] def extra_repr(self) -> str: return 'dim={dim}'.format(dim=self.dim)
class Softmax2d(Module): r"""Applies SoftMax over features to each spatial location. When given an image of ``Channels x Height x Width``, it will apply `Softmax` to each location :math:`(Channels, h_i, w_j)` Shape: - Input: :math:`(N, C, H, W)` or :math:`(C, H, W)`. - Output: :math:`(N, C, H, W)` or :math:`(C, H, W)` (same shape as input) Returns: a Tensor of the same dimension and shape as the input with values in the range [0, 1] Examples:: >>> m = nn.Softmax2d() >>> # you softmax over the 2nd dimension >>> input = torch.randn(2, 3, 12, 13) >>> output = m(input) """ def forward(self, input: Tensor) -> Tensor: assert input.dim() == 4 or input.dim() == 3, 'Softmax2d requires a 3D or 4D tensor as input' return F.softmax(input, -3, _stacklevel=5) class LogSoftmax(Module): r"""Applies the :math:`\log(\text{Softmax}(x))` function to an n-dimensional input Tensor. The LogSoftmax formulation can be simplified as: .. math:: \text{LogSoftmax}(x_{i}) = \log\left(\frac{\exp(x_i) }{ \sum_j \exp(x_j)} \right) Shape: - Input: :math:`(*)` where `*` means, any number of additional dimensions - Output: :math:`(*)`, same shape as the input Args: dim (int): A dimension along which LogSoftmax will be computed. Returns: a Tensor of the same dimension and shape as the input with values in the range [-inf, 0) Examples:: >>> m = nn.LogSoftmax(dim=1) >>> input = torch.randn(2, 3) >>> output = m(input) """ __constants__ = ['dim'] dim: Optional[int] def __init__(self, dim: Optional[int] = None) -> None: super(LogSoftmax, self).__init__() self.dim = dim def __setstate__(self, state): super().__setstate__(state) if not hasattr(self, 'dim'): self.dim = None def forward(self, input: Tensor) -> Tensor: return F.log_softmax(input, self.dim, _stacklevel=5) def extra_repr(self): return 'dim={dim}'.format(dim=self.dim)