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mindspore.nn.BatchNorm1d

class mindspore.nn.BatchNorm1d(num_features, eps=1e-05, momentum=0.9, affine=True, gamma_init='ones', beta_init='zeros', moving_mean_init='zeros', moving_var_init='ones', use_batch_statistics=None)

Batch Normalization layer over a 2D input.

Batch Normalization is widely used in convolutional networks. This layer applies Batch Normalization over a 2D input (a mini-batch of 1D inputs) to reduce internal covariate shift as described in the paper Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift. It rescales and recenters the feature using a mini-batch of data and the learned parameters which can be described in the following formula.

$$y=\frac{x-\mathrm{E}[x]}{\sqrt{\mathrm{Var}[x]+ϵ}}\ast \gamma +\beta$$

Note

The implementation of BatchNorm is different in graph mode and pynative mode, therefore the mode is not recommended to be changed after net was initialized.

Parameters

• num_features (int) – C from an expected input of size (N, C).

• eps (float) – A value added to the denominator for numerical stability. Default: 1e-5.

• momentum (float) – A floating hyperparameter of the momentum for the running_mean and running_var computation. Default: 0.9.

• affine (bool) – A bool value. When set to True, gamma and beta can be learned. Default: True.

• gamma_init (Union[Tensor, str, Initializer, numbers.Number]) – Initializer for the gamma weight. The values of str refer to the function initializer including ‘zeros’, ‘ones’, etc. Default: ‘ones’.

• beta_init (Union[Tensor, str, Initializer, numbers.Number]) – Initializer for the beta weight. The values of str refer to the function initializer including ‘zeros’, ‘ones’, etc. Default: ‘zeros’.

• moving_mean_init (Union[Tensor, str, Initializer, numbers.Number]) – Initializer for the moving mean. The values of str refer to the function initializer including ‘zeros’, ‘ones’, etc. Default: ‘zeros’.

• moving_var_init (Union[Tensor, str, Initializer, numbers.Number]) – Initializer for the moving variance. The values of str refer to the function initializer including ‘zeros’, ‘ones’, etc. Default: ‘ones’.

• use_batch_statistics (bool) – If true, use the mean value and variance value of current batch data. If false, use the mean value and variance value of specified value. If None, the training process will use the mean and variance of current batch data and track the running mean and variance, the evaluation process will use the running mean and variance. Default: None.

Inputs:

• x (Tensor) - Tensor of shape $(N,C_{in})$.

Outputs:

Tensor, the normalized, scaled, offset tensor, of shape $(N,C_{out})$.

Supported Platforms:

Ascend GPU CPU

Raises

• TypeError – If num_features is not an int.

• TypeError – If eps is not a float.

• ValueError – If num_features is less than 1.

• ValueError – If momentum is not in range [0, 1].

Examples

>>> import numpy as np
>>> import mindspore.nn as nn
>>> from mindspore import Tensor
>>> net = nn.BatchNorm1d(num_features=4)
>>> x = Tensor(np.array([[0.7, 0.5, 0.5, 0.6],
...                      [0.5, 0.4, 0.6, 0.9]]).astype(np.float32))
>>> output = net(x)
>>> print(output)
[[ 0.6999965   0.4999975  0.4999975  0.59999704 ]
 [ 0.4999975   0.399998   0.59999704 0.89999545 ]]