SpaceToDepth¶
Versioned name : SpaceToDepth-1
Category : Data movement
Short description : SpaceToDepth operation rearranges data from the spatial dimensions of the input tensor into depth dimension of the output tensor.
Attributes
block_size
Description : block_size specifies the size of the value block to be moved. The depth dimension size must be evenly divided by
block_size ^ (len(input.shape) - 2)
.Range of values : a positive integer
Type :
int
Default value : 1
Required : no
mode
Description : specifies how the output depth dimension is gathered from block coordinates and the old depth dimension.
Range of values :
blocks_first : the output depth is gathered from
[block_size, ..., block_size, C]
depth_first : the output depth is gathered from
[C, block_size, ..., block_size]
Type :
string
Default value : None
Required : yes
Inputs
1 :
data
- input tensor of any type with rank >= 3. Required.
Outputs
1 : permuted tensor with shape
[N, C * (block_size ^ K), D1 / block_size, D2 / block_size, ..., DK / block_size]
.
Detailed description
SpaceToDepth operation permutes element from the input tensor with shape [N, C, D1, D2, ..., DK]
, to the output tensor where values from the input spatial dimensions D1, D2, ..., DK
are moved to the new depth dimension. Refer to the ONNX* specification for an example of the 4D input tensor case.
The operation is equivalent to the following transformation of the input tensor data
with K
spatial dimensions of shape [N, C, D1, D2, ..., DK]
to Y output tensor. If mode = blocks_first
:
x' = reshape(data, [N, C, D1/block_size, block_size, D2/block_size, block_size, ... , DK/block_size, block_size])
x'' = transpose(x', [0, 3, 5, ..., K + (K + 1), 1, 2, 4, ..., K + K])
y = reshape(x'', [N, C * (block_size ^ K), D1 / block_size, D2 / block_size, ... , DK / block_size])
If mode = depth_first
:
x' = reshape(data, [N, C, D1/block_size, block_size, D2/block_size, block_size, ..., DK/block_size, block_size])
x'' = transpose(x', [0, 1, 3, 5, ..., K + (K + 1), 2, 4, ..., K + K])
y = reshape(x'', [N, C * (block_size ^ K), D1 / block_size, D2 / block_size, ..., DK / block_size])
Example
<layer type="SpaceToDepth" ...>
<data block_size="2" mode="blocks_first"/>
<input>
<port id="0">
<dim>5</dim>
<dim>7</dim>
<dim>4</dim>
<dim>6</dim>
</port>
</input>
<output>
<port id="1">
<dim>5</dim> <!-- data.shape[0] -->
<dim>28</dim> <!-- data.shape[1] * (block_size ^ 2) -->
<dim>2</dim> <!-- data.shape[2] / block_size -->
<dim>3</dim> <!-- data.shape[3] / block_size -->
</port>
</output>
</layer>