- class torch.nn.BatchNorm1d(num_features, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True, device=None, dtype=None)¶
Applies Batch Normalization over a 2D or 3D input as described in the paper Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift .
The mean and standard-deviation are calculated per-dimension over the mini-batches and and are learnable parameter vectors of size C (where C is the number of features or channels of the input). By default, the elements of are set to 1 and the elements of are set to 0. At train time in the forward pass, the standard-deviation is calculated via the biased estimator, equivalent to
torch.var(input, unbiased=False). However, the value stored in the moving average of the standard-deviation is calculated via the unbiased estimator, equivalent to
Also 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
track_running_statsis set to
False, this layer then does not keep running estimates, and batch statistics are instead used during evaluation time as well.
momentumargument is different from one used in optimizer classes and the conventional notion of momentum. Mathematically, the update rule for running statistics here is , where is the estimated statistic and is the new observed value.
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.
num_features (int) – number of features or channels of the input
eps (float) – a value added to the denominator for numerical stability. Default: 1e-5
momentum (float) – the value used for the running_mean and running_var computation. Can be set to
Nonefor cumulative moving average (i.e. simple average). Default: 0.1
affine (bool) – a boolean value that when set to
True, this module has learnable affine parameters. Default:
track_running_stats (bool) – a boolean value that when set to
True, this module tracks the running mean and variance, and when set to
False, this module does not track such statistics, and initializes statistics buffers
None. When these buffers are
None, this module always uses batch statistics. in both training and eval modes. Default:
Input: or , where is the batch size, is the number of features or channels, and is the sequence length
Output: or (same shape as input)
>>> # With Learnable Parameters >>> m = nn.BatchNorm1d(100) >>> # Without Learnable Parameters >>> m = nn.BatchNorm1d(100, affine=False) >>> input = torch.randn(20, 100) >>> output = m(input)