# BatchNorm1d¶

class BatchNorm1d(num_features, eps=1e-05, momentum=0.9, affine=True, track_running_stats=True, freeze=False, **kwargs)[源代码]

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

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

The mean and standard-deviation are calculated per-dimension over the mini-batches and $$\gamma$$ and $$\beta$$ are learnable parameter vectors of size C (where C is the number of features or channels of the input). By default, the elements of $$\gamma$$ are set to 1 and the elements of $$\beta$$ are set to 0. The standard-deviation is calculated via the biased estimator, equivalent to torch.var(input, unbiased=False).

By default, during training this layer keeps running estimates of its computed mean and variance, which are then used for normalization during evaluation. The running estimates are kept with a default momentum of 0.9.

If track_running_stats is set to False, this layer then does not keep running estimates, and batch statistics are instead used during evaluation time as well.

Because the Batch Normalization is done over the C dimension, computing statistics on (N, L) slices, it’s common terminology to call this Temporal Batch Normalization.

The update formula for running_mean and running_var (taking running_mean as an example) is

$\textrm{running_mean} = \textrm{momentum} \times \textrm{running_mean} + (1 - \textrm{momentum}) \times \textrm{batch_mean}$

which could be defined differently in other frameworks. Most notably, momentum of 0.1 in PyTorch is equivalent to mementum of 0.9 here.

Shape:
• Input: $$(N, C)$$ or $$(N, C, L)$$, where $$N$$ is the batch size, $$C$$ is the number of features or channels, and $$L$$ is the sequence length

• Output: $$(N, C)$$ or $$(N, C, L)$$ (same shape as input)