# InstanceNorm¶

class paddle.fluid.dygraph.nn. InstanceNorm ( num_channels, epsilon=1e-05, param_attr=None, bias_attr=None, dtype='float32' ) [source]

This interface is used to construct a callable object of the InstanceNorm class. For more details, refer to code examples.

Can be used as a normalizer function for convolution or fully_connected operations. The required data format for this layer is one of the following:

DataLayout: NCHW [batch, in_channels, in_height, in_width]

Refer to Instance Normalization: The Missing Ingredient for Fast Stylization for more details.

$$input$$ is the input features over a mini-batch.

$\begin{split}\\mu_{\\beta} &\\gets \\frac{1}{HW} \\sum_{i=1}^{HW} x_i \\qquad &//\\ \\ mean\ of\ one\ feature\ map\ in\ mini-batch \\\\ \\sigma_{\\beta}^{2} &\\gets \\frac{1}{HW} \\sum_{i=1}^{HW}(x_i - \\ \\mu_{\\beta})^2 \\qquad &//\ variance\ of\ one\ feature\ map\ in\ mini-batch \\\\ \\hat{x_i} &\\gets \\frac{x_i - \\mu_\\beta} {\\sqrt{\\ \\sigma_{\\beta}^{2} + \\epsilon}} \\qquad &//\ normalize \\\\ y_i &\\gets \\gamma \\hat{x_i} + \\beta \\qquad &//\ scale\ and\ shift\end{split}$

Note

H means height of feature map, W means width of feature map.

Parameters
• num_channels (int) – Indicate the number of channels of the input Tensor.

• epsilon (float, optional) – A value added to the denominator for numerical stability. Default is 1e-5.

• param_attr (ParamAttr|bool, optional) – The parameter attribute for Parameter scale of instance_norm. If it is set to None or one attribute of ParamAttr, instance_norm will create ParamAttr as param_attr, the name of scale can be set in ParamAttr. If the Initializer of the param_attr is not set, the parameter is initialized one. If it is set to False, will not create param_attr. Default: None.

• bias_attr (ParamAttr|bool, optional) – The parameter attribute for the bias of instance_norm. If it is set to None or one attribute of ParamAttr, instance_norm will create ParamAttr as bias_attr, the name of bias can be set in ParamAttr. If the Initializer of the bias_attr is not set, the bias is initialized zero. If it is set to False, will not create bias_attr. Default: None.

• dtype (str, optional) – Indicate the data type of the input Tensor, which can be float32 or float64. Default: float32.

Returns

None.

Examples

import numpy as np

# x's shape is [1, 3, 1, 2]
x = np.array([[[[1.0, 8.0]], [[10.0, 5.0]], [[4.0, 6.0]]]]).astype('float32')
with fluid.dygraph.guard():
x = to_variable(x)