# 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.

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.

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])
```

Attributes

• block_size

• Description: specifies the size of the value block to be moved. The spatial dimensions must be evenly divided by `block_size`.

• 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`

• Required: yes

Inputs

• 1: `data` - input tensor of type T with rank >= 3. Required.

Outputs

• 1: permuted tensor of type T and shape ```[N, C * (block_size ^ K), D1 / block_size, D2 / block_size, ..., DK / block_size]```.

Types

• T: any supported type.

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>
```