mlx.nn.BatchNorm#

class BatchNorm(num_features: int, eps: float = 1e-05, momentum: float = 0.1, affine: bool = True, track_running_stats: bool = True)#

Applies Batch Normalization over a 2D or 3D input.

Computes

\[y = \frac{x - E[x]}{\sqrt{Var[x]} + \epsilon} \gamma + \beta,\]

where \(\gamma\) and \(\beta\) are learned per feature dimension parameters initialized at 1 and 0 respectively.

The input shape is specified as NC or NLC, where N is the batch, C is the number of features or channels, and L is the sequence length. The output has the same shape as the input. For four-dimensional arrays, the shape is NHWC, where H and W are the height and width respectively.

For more information on Batch Normalization, see the original paper Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift.

Parameters:

  • num_features (int) – The feature dimension to normalize over.

  • eps (float, optional) – A small additive constant for numerical stability. Default: 1e-5.

  • momentum (float, optional) – The momentum for updating the running mean and variance. Default: 0.1.

  • affine (bool, optional) – If True, apply a learned affine transformation after the normalization. Default: True.

  • track_running_stats (bool, optional) – If True, track the running mean and variance. Default: True.

Examples

>>> import mlx.core as mx
>>> import mlx.nn as nn
>>> x = mx.random.normal((5, 4))
>>> bn = nn.BatchNorm(num_features=4, affine=True)
>>> output = bn(x)