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tf.nn.with_space_to_batch

TensorFlow 1 version View source on GitHub

Performs op on the space-to-batch representation of input.

This has the effect of transforming sliding window operations into the corresponding "atrous" operation in which the input is sampled at the specified dilation_rate.

In the special case that dilation_rate is uniformly 1, this simply returns:

op(input, num_spatial_dims, padding)

Otherwise, it returns:

batch_to_space_nd( op(space_to_batch_nd(input, adjusted_dilation_rate, adjusted_paddings), num_spatial_dims, "VALID") adjusted_dilation_rate, adjusted_crops),

where:

adjusted_dilation_rate is an int64 tensor of shape [max(spatialdims)], adjusted{paddings,crops} are int64 tensors of shape [max(spatial_dims), 2]

defined as follows:

We first define two int64 tensors paddings and crops of shape [num_spatial_dims, 2] based on the value of padding and the spatial dimensions of the input:

If padding = "VALID", then:

paddings, crops = required_space_to_batch_paddings( input_shape[spatial_dims], dilation_rate)

If padding = "SAME", then:

dilated_filter_shape = filter_shape + (filter_shape - 1) * (dilation_rate - 1)

paddings, crops = required_space_to_batch_paddings( input_shape[spatial_dims], dilation_rate, [(dilated_filter_shape - 1) // 2, dilated_filter_shape - 1 - (dilated_filter_shape - 1) // 2])

Because space_to_batch_nd and batch_to_space_nd assume that the spatial dimensions are contiguous starting at the second dimension, but the specified spatial_dims may not be, we must adjust dilation_rate, paddings and crops in order to be usable with these operations. For a given dimension, if the block size is 1, and both the starting and ending padding and crop amounts are 0, then space_to_batch_nd effectively leaves that dimension alone, which is what is needed for dimensions not part of spatial_dims. Furthermore, space_to_batch_nd and batch_to_space_nd handle this case efficiently for any number of leading and trailing dimensions.

For 0 <= i < len(spatial_dims), we assign:

adjusted_dilation_rate[spatial_dims[i] - 1] = dilation_rate[i] adjusted_paddings[spatial_dims[i] - 1, :] = paddings[i, :] adjusted_crops[spatial_dims[i] - 1, :] = crops[i, :]

All unassigned values of adjusted_dilation_rate default to 1, while all unassigned values of adjusted_paddings and adjusted_crops default to 0.

Note in the case that dilation_rate is not uniformly 1, specifying "VALID" padding is equivalent to specifying padding = "SAME" with a filter_shape of [1]*N.

Advanced usage. Note the following optimization: A sequence of with_space_to_batch operations with identical (not uniformly 1) dilation_rate parameters and "VALID" padding

net = with_space_to_batch(net, dilation_rate, "VALID", op_1) ... net = with_space_to_batch(net, dilation_rate, "VALID", op_k)

can be combined into a single with_space_to_batch operation as follows:

def combined_op(converted_input, num_spatial_dims, _): result = op_1(converted_input, num_spatial_dims, "VALID") ... result = op_k(result, num_spatial_dims, "VALID")

net = with_space_to_batch(net, dilation_rate, "VALID", combined_op)

This eliminates the overhead of k-1 calls to space_to_batch_nd and batch_to_space_nd.

Similarly, a sequence of with_space_to_batch operations with identical (not uniformly 1) dilation_rate parameters, "SAME" padding, and odd filter dimensions

net = with_space_to_batch(net, dilation_rate, "SAME", op_1, filter_shape_1) ... net = with_space_to_batch(net, dilation_rate, "SAME", op_k, filter_shape_k)

can be combined into a single with_space_to_batch operation as follows:

def combined_op(converted_input, num_spatial_dims, _): result = op_1(converted_input, num_spatial_dims, "SAME") ... result = op_k(result, num_spatial_dims, "SAME")

net = with_space_to_batch(net, dilation_rate, "VALID", combined_op)

input Tensor of rank > max(spatial_dims).
dilation_rate int32 Tensor of known shape [num_spatial_dims].
padding str constant equal to "VALID" or "SAME"
op Function that maps (input, num_spatial_dims, padding) -> output
filter_shape If padding = "SAME", specifies the shape of the convolution kernel/pooling window as an integer Tensor of shape [>=num_spatial_dims]. If padding = "VALID", filter_shape is ignored and need not be specified.
spatial_dims Monotonically increasing sequence of num_spatial_dims integers (which are >= 1) specifying the spatial dimensions of input and output. Defaults to: range(1, num_spatial_dims+1).
data_format A string or None. Specifies whether the channel dimension of the input and output is the last dimension (default, or if data_format does not start with "NC"), or the second dimension (if data_format starts with "NC"). For N=1, the valid values are "NWC" (default) and "NCW". For N=2, the valid values are "NHWC" (default) and "NCHW". For N=3, the valid values are "NDHWC" (default) and "NCDHW".

The output Tensor as described above, dimensions will vary based on the op provided.

ValueError if padding is invalid or the arguments are incompatible.
ValueError if spatial_dims are invalid.