Conv1d¶

class
torch.nn.
Conv1d
(in_channels: int, out_channels: int, kernel_size: Union[T, Tuple[T]], stride: Union[T, Tuple[T]] = 1, padding: Union[T, Tuple[T]] = 0, dilation: Union[T, Tuple[T]] = 1, groups: int = 1, bias: bool = True, padding_mode: str = 'zeros')[source]¶ Applies a 1D convolution over an input signal composed of several input planes.
In the simplest case, the output value of the layer with input size $(N, C_{\text{in}}, L)$ and output $(N, C_{\text{out}}, L_{\text{out}})$ can be precisely described as:
$\text{out}(N_i, C_{\text{out}_j}) = \text{bias}(C_{\text{out}_j}) + \sum_{k = 0}^{C_{in}  1} \text{weight}(C_{\text{out}_j}, k) \star \text{input}(N_i, k)$where $\star$ is the valid crosscorrelation operator, $N$ is a batch size, $C$ denotes a number of channels, $L$ is a length of signal sequence.
stride
controls the stride for the crosscorrelation, a single number or a oneelement tuple.padding
controls the amount of implicit zeropaddings on both sides forpadding
number of points.dilation
controls the spacing between the kernel points; also known as the à trous algorithm. It is harder to describe, but this link has a nice visualization of whatdilation
does.groups
controls the connections between inputs and outputs.in_channels
andout_channels
must both be divisible bygroups
. For example,At groups=1, all inputs are convolved to all outputs.
At groups=2, the operation becomes equivalent to having two conv layers side by side, each seeing half the input channels, and producing half the output channels, and both subsequently concatenated.
At groups=
in_channels
, each input channel is convolved with its own set of filters, of size $\left\lfloor\frac{out\_channels}{in\_channels}\right\rfloor$ .
Note
Depending of the size of your kernel, several (of the last) columns of the input might be lost, because it is a valid crosscorrelation, and not a full crosscorrelation. It is up to the user to add proper padding.
Note
When groups == in_channels and out_channels == K * in_channels, where K is a positive integer, this operation is also termed in literature as depthwise convolution.
In other words, for an input of size $(N, C_{in}, L_{in})$ , a depthwise convolution with a depthwise multiplier K, can be constructed by arguments $(C_\text{in}=C_{in}, C_\text{out}=C_{in} \times K, ..., \text{groups}=C_{in})$ .
Note
In some circumstances when using the CUDA backend with CuDNN, this operator may select a nondeterministic algorithm to increase performance. If this is undesirable, you can try to make the operation deterministic (potentially at a performance cost) by setting
torch.backends.cudnn.deterministic = True
. Please see the notes on Reproducibility for background. Parameters
in_channels (int) – Number of channels in the input image
out_channels (int) – Number of channels produced by the convolution
stride (int or tuple, optional) – Stride of the convolution. Default: 1
padding (int or tuple, optional) – Zeropadding added to both sides of the input. Default: 0
padding_mode (string, optional) –
'zeros'
,'reflect'
,'replicate'
or'circular'
. Default:'zeros'
dilation (int or tuple, optional) – Spacing between kernel elements. Default: 1
groups (int, optional) – Number of blocked connections from input channels to output channels. Default: 1
bias (bool, optional) – If
True
, adds a learnable bias to the output. Default:True
 Shape:
Input: $(N, C_{in}, L_{in})$
Output: $(N, C_{out}, L_{out})$ where
$L_{out} = \left\lfloor\frac{L_{in} + 2 \times \text{padding}  \text{dilation} \times (\text{kernel\_size}  1)  1}{\text{stride}} + 1\right\rfloor$
 Variables
~Conv1d.weight (Tensor) – the learnable weights of the module of shape $(\text{out\_channels}, \frac{\text{in\_channels}}{\text{groups}}, \text{kernel\_size})$ . The values of these weights are sampled from $\mathcal{U}(\sqrt{k}, \sqrt{k})$ where $k = \frac{groups}{C_\text{in} * \text{kernel\_size}}$
~Conv1d.bias (Tensor) – the learnable bias of the module of shape (out_channels). If
bias
isTrue
, then the values of these weights are sampled from $\mathcal{U}(\sqrt{k}, \sqrt{k})$ where $k = \frac{groups}{C_\text{in} * \text{kernel\_size}}$
Examples:
>>> m = nn.Conv1d(16, 33, 3, stride=2) >>> input = torch.randn(20, 16, 50) >>> output = m(input)