LayerNorm

class paddle.nn. LayerNorm ( normalized_shape: int | Sequence[int], epsilon: float = 1e-05, weight_attr: bool | ParamAttr | None = None, bias_attr: bool | ParamAttr | None = None, name: str | None = None ) [source]

Construct a callable object of the LayerNorm class. For more details, refer to code examples. It implements the function of the Layer Normalization Layer and can be applied to mini-batch input data. Refer to Layer Normalization

The formula is as follows:

\[ \begin{align}\begin{aligned}\mu & = \frac{1}{H}\sum_{i=1}^{H} x_i\\\sigma & = \sqrt{\frac{1}{H}\sum_{i=1}^{H}{(x_i - \mu)^2} + \epsilon}\\y & = f(\frac{g}{\sigma}(x - \mu) + b)\end{aligned}\end{align} \]

  • \(x\): the vector representation of the summed inputs to the neurons in that layer.

  • \(H\): the number of hidden units in a layers

  • \(\epsilon\): the small value added to the variance to prevent division by zero.

  • \(g\): the trainable scale parameter.

  • \(b\): the trainable bias parameter.

Parameters

  • normalized_shape (int|list|tuple) – Input shape from an expected input of size [*, normalized_shape[0], normalized_shape[1], ..., normalized_shape[-1]] . If it is a single integer, this module will normalize over the last dimension which is expected to be of that specific size.

  • epsilon (float, optional) – The small value added to the variance to prevent division by zero. Default: 1e-05.

  • weight_attr (ParamAttr|bool|None, optional) – The parameter attribute for the learnable gain \(g\). If False, weight is None. If is None, a default ParamAttr would be added as scale. The param_attr is initialized as 1 if it is added. Default: None. For more information, please refer to ParamAttr .

  • bias_attr (ParamAttr|bool|None, optional) – The parameter attribute for the learnable bias \(b\). If is False, bias is None. If is None, a default ParamAttr would be added as bias. The bias_attr is initialized as 0 if it is added. Default: None. For more information, please refer to ParamAttr .

  • name (str|None, optional) – Name for the LayerNorm, default is None. For more information, please refer to Name .

Shape:

  • x: 2-D, 3-D, 4-D or 5-D tensor.

  • output: same shape as input x.

Returns

Tensor , the dimension is the same as x, but the internal values have been normalized by LayerNorm .

Examples

>>> import paddle
>>> paddle.seed(100)
>>> x = paddle.rand((2, 2, 2, 3))
>>> layer_norm = paddle.nn.LayerNorm(x.shape[1:])
>>> layer_norm_out = layer_norm(x)

>>> print(layer_norm_out)
Tensor(shape=[2, 2, 2, 3], dtype=float32, place=Place(cpu), stop_gradient=False,
[[[[ 0.60520101, -0.67670590, -1.40020895],
   [ 0.46540466, -0.09736638, -0.47771254]],
  [[-0.74365306,  0.63718957, -1.41333175],
   [ 1.44764745, -0.25489068,  1.90842617]]],
 [[[ 1.09773350,  1.49568415, -0.45503747],
   [-1.01755989,  1.08368254, -0.38671425]],
  [[-0.62252408,  0.60490781,  0.13109133],
   [-0.81222653,  0.84285998, -1.96189952]]]])
forward ( input: Tensor ) → Tensor

forward

Defines the computation performed at every call. Should be overridden by all subclasses.

Parameters

  • *inputs (tuple) – unpacked tuple arguments

  • **kwargs (dict) – unpacked dict arguments

extra_repr ( ) → str

extra_repr

Extra representation of this layer, you can have custom implementation of your own layer.