Tensor Transformations

Note: Functions taking Tensor arguments can also take anything accepted by tf.convert_to_tensor.

[TOC]

Casting

TensorFlow provides several operations that you can use to cast tensor data types in your graph.

`tf.string_to_number(string_tensor, out_type=None, name=None)`

Converts each string in the input Tensor to the specified numeric type.

(Note that int32 overflow results in an error while float overflow results in a rounded value.)

Args:

string_tensor: A Tensor of type string.
out_type: An optional tf.DType from: tf.float32, tf.int32. Defaults to tf.float32. The numeric type to interpret each string in string_tensor as.
name: A name for the operation (optional).

Returns:

A Tensor of type out_type. A Tensor of the same shape as the input string_tensor.

`tf.to_double(x, name='ToDouble')`

Casts a tensor to type float64.

Args:

x: A Tensor or SparseTensor.
name: A name for the operation (optional).

Returns:

A Tensor or SparseTensor with same shape as x with type float64.

Raises:

TypeError: If x cannot be cast to the float64.

`tf.to_float(x, name='ToFloat')`

Casts a tensor to type float32.

Args:

x: A Tensor or SparseTensor.
name: A name for the operation (optional).

Returns:

A Tensor or SparseTensor with same shape as x with type float32.

Raises:

TypeError: If x cannot be cast to the float32.

`tf.to_bfloat16(x, name='ToBFloat16')`

Casts a tensor to type bfloat16.

Args:

x: A Tensor or SparseTensor.
name: A name for the operation (optional).

Returns:

A Tensor or SparseTensor with same shape as x with type bfloat16.

Raises:

TypeError: If x cannot be cast to the bfloat16.

`tf.to_int32(x, name='ToInt32')`

Casts a tensor to type int32.

Args:

x: A Tensor or SparseTensor.
name: A name for the operation (optional).

Returns:

A Tensor or SparseTensor with same shape as x with type int32.

Raises:

TypeError: If x cannot be cast to the int32.

`tf.to_int64(x, name='ToInt64')`

Casts a tensor to type int64.

Args:

x: A Tensor or SparseTensor.
name: A name for the operation (optional).

Returns:

A Tensor or SparseTensor with same shape as x with type int64.

Raises:

TypeError: If x cannot be cast to the int64.

`tf.cast(x, dtype, name=None)`

Casts a tensor to a new type.

The operation casts x (in case of Tensor) or x.values (in case of SparseTensor) to dtype.

For example:

# tensor `a` is [1.8, 2.2], dtype=tf.float
tf.cast(a, tf.int32) ==> [1, 2]  # dtype=tf.int32

Args:

x: A Tensor or SparseTensor.
dtype: The destination type.
name: A name for the operation (optional).

Returns:

A Tensor or SparseTensor with same shape as x.

Raises:

TypeError: If x cannot be cast to the dtype.

`tf.saturate_cast(value, dtype, name=None)`

Performs a safe saturating cast of value to dtype.

This function casts the input to dtype without applying any scaling. If there is a danger that values would over or underflow in the cast, this op applies the appropriate clamping before the cast.

Args:

value: A Tensor.
dtype: The desired output DType.
name: A name for the operation (optional).

Returns:

value safely cast to dtype.

Shapes and Shaping

TensorFlow provides several operations that you can use to determine the shape of a tensor and change the shape of a tensor.

`tf.shape(input, name=None)`

Returns the shape of a tensor.

This operation returns a 1-D integer tensor representing the shape of input.

For example:

# 't' is [[[1, 1, 1], [2, 2, 2]], [[3, 3, 3], [4, 4, 4]]]
shape(t) ==> [2, 2, 3]

Args:

input: A Tensor.
name: A name for the operation (optional).

Returns:

A Tensor of type int32.

`tf.size(input, name=None)`

Returns the size of a tensor.

This operation returns an integer representing the number of elements in input.

For example:

# 't' is [[[1, 1,, 1], [2, 2, 2]], [[3, 3, 3], [4, 4, 4]]]]
size(t) ==> 12

Args:

input: A Tensor.
name: A name for the operation (optional).

Returns:

A Tensor of type int32.

`tf.rank(input, name=None)`

Returns the rank of a tensor.

This operation returns an integer representing the rank of input.

For example:

# 't' is [[[1, 1, 1], [2, 2, 2]], [[3, 3, 3], [4, 4, 4]]]
# shape of tensor 't' is [2, 2, 3]
rank(t) ==> 3

Note: The rank of a tensor is not the same as the rank of a matrix. The rank of a tensor is the number of indices required to uniquely select each element of the tensor. Rank is also known as "order", "degree", or "ndims."

Args:

input: A Tensor or SparseTensor.
name: A name for the operation (optional).

Returns:

A Tensor of type int32.

`tf.reshape(tensor, shape, name=None)`

Reshapes a tensor.

Given tensor, this operation returns a tensor that has the same values as tensor with shape shape.

If one component of shape is the special value -1, the size of that dimension is computed so that the total size remains constant. In particular, a shape of [-1] flattens into 1-D. At most one component of shape can be -1.

If shape is 1-D or higher, then the operation returns a tensor with shape shape filled with the values of tensor. In this case, the number of elements implied by shape must be the same as the number of elements in tensor.

For example:

# tensor 't' is [1, 2, 3, 4, 5, 6, 7, 8, 9]
# tensor 't' has shape [9]
reshape(t, [3, 3]) ==> [[1, 2, 3],
                        [4, 5, 6],
                        [7, 8, 9]]

# tensor 't' is [[[1, 1], [2, 2]],
#                [[3, 3], [4, 4]]]
# tensor 't' has shape [2, 2, 2]
reshape(t, [2, 4]) ==> [[1, 1, 2, 2],
                        [3, 3, 4, 4]]

# tensor 't' is [[[1, 1, 1],
#                 [2, 2, 2]],
#                [[3, 3, 3],
#                 [4, 4, 4]],
#                [[5, 5, 5],
#                 [6, 6, 6]]]
# tensor 't' has shape [3, 2, 3]
# pass '[-1]' to flatten 't'
reshape(t, [-1]) ==> [1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6]

# -1 can also be used to infer the shape

# -1 is inferred to be 9:
reshape(t, [2, -1]) ==> [[1, 1, 1, 2, 2, 2, 3, 3, 3],
                         [4, 4, 4, 5, 5, 5, 6, 6, 6]]
# -1 is inferred to be 2:
reshape(t, [-1, 9]) ==> [[1, 1, 1, 2, 2, 2, 3, 3, 3],
                         [4, 4, 4, 5, 5, 5, 6, 6, 6]]
# -1 is inferred to be 3:
reshape(t, [ 2, -1, 3]) ==> [[[1, 1, 1],
                              [2, 2, 2],
                              [3, 3, 3]],
                             [[4, 4, 4],
                              [5, 5, 5],
                              [6, 6, 6]]]

# tensor 't' is [7]
# shape `[]` reshapes to a scalar
reshape(t, []) ==> 7

Args:

tensor: A Tensor.
shape: A Tensor of type int32. Defines the shape of the output tensor.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as tensor.

`tf.squeeze(input, squeeze_dims=None, name=None)`

Removes dimensions of size 1 from the shape of a tensor.

Given a tensor input, this operation returns a tensor of the same type with all dimensions of size 1 removed. If you don't want to remove all size 1 dimensions, you can remove specific size 1 dimensions by specifying squeeze_dims.

For example:

# 't' is a tensor of shape [1, 2, 1, 3, 1, 1]
shape(squeeze(t)) ==> [2, 3]

Or, to remove specific size 1 dimensions:

# 't' is a tensor of shape [1, 2, 1, 3, 1, 1]
shape(squeeze(t, [2, 4])) ==> [1, 2, 3, 1]

Args:

input: A Tensor. The input to squeeze.
squeeze_dims: An optional list of ints. Defaults to []. If specified, only squeezes the dimensions listed. The dimension index starts at 0. It is an error to squeeze a dimension that is not 1.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input. Contains the same data as input, but has one or more dimensions of size 1 removed.

`tf.expand_dims(input, dim, name=None)`

Inserts a dimension of 1 into a tensor's shape.

Given a tensor input, this operation inserts a dimension of 1 at the dimension index dim of input's shape. The dimension index dim starts at zero; if you specify a negative number for dim it is counted backward from the end.

This operation is useful if you want to add a batch dimension to a single element. For example, if you have a single image of shape [height, width, channels], you can make it a batch of 1 image with expand_dims(image, 0), which will make the shape [1, height, width, channels].

Other examples:

# 't' is a tensor of shape [2]
shape(expand_dims(t, 0)) ==> [1, 2]
shape(expand_dims(t, 1)) ==> [2, 1]
shape(expand_dims(t, -1)) ==> [2, 1]

# 't2' is a tensor of shape [2, 3, 5]
shape(expand_dims(t2, 0)) ==> [1, 2, 3, 5]
shape(expand_dims(t2, 2)) ==> [2, 3, 1, 5]
shape(expand_dims(t2, 3)) ==> [2, 3, 5, 1]

This operation requires that:

-1-input.dims() <= dim <= input.dims()

This operation is related to squeeze(), which removes dimensions of size 1.

Args:

input: A Tensor.
dim: A Tensor of type int32. 0-D (scalar). Specifies the dimension index at which to expand the shape of input.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input. Contains the same data as input, but its shape has an additional dimension of size 1 added.

Slicing and Joining

TensorFlow provides several operations to slice or extract parts of a tensor, or join multiple tensors together.

`tf.slice(input_, begin, size, name=None)`

Extracts a slice from a tensor.

This operation extracts a slice of size size from a tensor input starting at the location specified by begin. The slice size is represented as a tensor shape, where size[i] is the number of elements of the 'i'th dimension of input that you want to slice. The starting location (begin) for the slice is represented as an offset in each dimension of input. In other words, begin[i] is the offset into the 'i'th dimension of input that you want to slice from.

begin is zero-based; size is one-based. If size[i] is -1, all remaining elements in dimension i are included in the slice. In other words, this is equivalent to setting:

size[i] = input.dim_size(i) - begin[i]

This operation requires that:

0 <= begin[i] <= begin[i] + size[i] <= Di for i in [0, n]

For example:

# 'input' is [[[1, 1, 1], [2, 2, 2]],
#             [[3, 3, 3], [4, 4, 4]],
#             [[5, 5, 5], [6, 6, 6]]]
tf.slice(input, [1, 0, 0], [1, 1, 3]) ==> [[[3, 3, 3]]]
tf.slice(input, [1, 0, 0], [1, 2, 3]) ==> [[[3, 3, 3],
                                            [4, 4, 4]]]
tf.slice(input, [1, 0, 0], [2, 1, 3]) ==> [[[3, 3, 3]],
                                           [[5, 5, 5]]]

Args:

input_: A Tensor.
begin: An int32 or int64 Tensor.
size: An int32 or int64 Tensor.
name: A name for the operation (optional).

Returns:

A Tensor the same type as input.

`tf.split(split_dim, num_split, value, name='split')`

Splits a tensor into num_split tensors along one dimension.

Splits value along dimension split_dim into num_split smaller tensors. Requires that num_split evenly divide value.shape[split_dim].

For example:

# 'value' is a tensor with shape [5, 30]
# Split 'value' into 3 tensors along dimension 1
split0, split1, split2 = tf.split(1, 3, value)
tf.shape(split0) ==> [5, 10]

Args:

split_dim: A 0-D int32 Tensor. The dimension along which to split. Must be in the range [0, rank(value)).
num_split: A Python integer. The number of ways to split.
value: The Tensor to split.
name: A name for the operation (optional).

Returns:

num_split Tensor objects resulting from splitting value.

`tf.tile(input, multiples, name=None)`

Constructs a tensor by tiling a given tensor.

This operation creates a new tensor by replicating input multiples times. The output tensor's i'th dimension has input.dims(i) * multiples[i] elements, and the values of input are replicated multiples[i] times along the 'i'th dimension. For example, tiling [a b c d] by [2] produces [a b c d a b c d].

Args:

input: A Tensor. 1-D or higher.
multiples: A Tensor of type int32. 1-D. Length must be the same as the number of dimensions in input
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input.

`tf.pad(tensor, paddings, mode='CONSTANT', name=None)`

Pads a tensor.

This operation pads a tensor according to the paddings you specify. paddings is an integer tensor with shape [n, 2], where n is the rank of tensor. For each dimension D of input, paddings[D, 0] indicates how many values to add before the contents of tensor in that dimension, and paddings[D, 1] indicates how many values to add after the contents of tensor in that dimension. If mode is "REFLECT" then both paddings[D, 0] and paddings[D, 1] must be no greater than tensor.dim_size(D) - 1. If mode is "SYMMETRIC" then both paddings[D, 0] and paddings[D, 1] must be no greater than tensor.dim_size(D).

The padded size of each dimension D of the output is:

paddings[D, 0] + tensor.dim_size(D) + paddings[D, 1]

For example:

# 't' is [[1, 2, 3], [4, 5, 6]].
# 'paddings' is [[1, 1,], [2, 2]].
# rank of 't' is 2.
pad(t, paddings, "CONSTANT") ==> [[0, 0, 0, 0, 0, 0, 0],
                                  [0, 0, 1, 2, 3, 0, 0],
                                  [0, 0, 4, 5, 6, 0, 0],
                                  [0, 0, 0, 0, 0, 0, 0]]

pad(t, paddings, "REFLECT") ==> [[6, 5, 4, 5, 6, 5, 4],
                                 [3, 2, 1, 2, 3, 2, 1],
                                 [6, 5, 4, 5, 6, 5, 4],
                                 [3, 2, 1, 2, 3, 2, 1]]

pad(t, paddings, "SYMMETRIC") ==> [[2, 1, 1, 2, 3, 3, 2],
                                   [2, 1, 1, 2, 3, 3, 2],
                                   [5, 4, 4, 5, 6, 6, 5],
                                   [5, 4, 4, 5, 6, 6, 5]]

Args:

tensor: A Tensor.
paddings: A Tensor of type int32.
mode: One of "CONSTANT", "REFLECT", or "SYMMETRIC".
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as tensor.

Raises:

ValueError: When mode is not one of "CONSTANT", "REFLECT", or "SYMMETRIC".

`tf.concat(concat_dim, values, name='concat')`

Concatenates tensors along one dimension.

Concatenates the list of tensors values along dimension concat_dim. If values[i].shape = [D0, D1, ... Dconcat_dim(i), ...Dn], the concatenated result has shape

[D0, D1, ... Rconcat_dim, ...Dn]

where

Rconcat_dim = sum(Dconcat_dim(i))

That is, the data from the input tensors is joined along the concat_dim dimension.

The number of dimensions of the input tensors must match, and all dimensions except concat_dim must be equal.

For example:

t1 = [[1, 2, 3], [4, 5, 6]]
t2 = [[7, 8, 9], [10, 11, 12]]
tf.concat(0, [t1, t2]) ==> [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]]
tf.concat(1, [t1, t2]) ==> [[1, 2, 3, 7, 8, 9], [4, 5, 6, 10, 11, 12]]

# tensor t3 with shape [2, 3]
# tensor t4 with shape [2, 3]
tf.shape(tf.concat(0, [t3, t4])) ==> [4, 3]
tf.shape(tf.concat(1, [t3, t4])) ==> [2, 6]

Args:

concat_dim: 0-D int32 Tensor. Dimension along which to concatenate.
values: A list of Tensor objects or a single Tensor.
name: A name for the operation (optional).

Returns:

A Tensor resulting from concatenation of the input tensors.

`tf.pack(values, name='pack')`

Packs a list of rank-R tensors into one rank-(R+1) tensor.

Packs tensors in values into a tensor with rank one higher than each tensor in values and shape [len(values)] + values[0].shape. The output satisfies output[i, ...] = values[i][...].

This is the opposite of unpack. The numpy equivalent is

tf.pack([x, y, z]) = np.asarray([x, y, z])

Args:

values: A list of Tensor objects with the same shape and type.
name: A name for this operation (optional).

Returns:

output: A packed Tensor with the same type as values.

`tf.unpack(value, num=None, name='unpack')`

Unpacks the outer dimension of a rank-R tensor into rank-(R-1) tensors.

Unpacks num tensors from value along the first dimension. If num is not specified (the default), it is inferred from value's shape. If value.shape[0] is not known, ValueError is raised.

The ith tensor in output is the slice value[i, ...]. Each tensor in output has shape value.shape[1:].

This is the opposite of pack. The numpy equivalent is

tf.unpack(x, n) = list(x)

Args:

value: A rank R > 0 Tensor to be unpacked.
num: An int. The first dimension of value. Automatically inferred if None (the default).
name: A name for the operation (optional).

Returns:

The list of Tensor objects unpacked from value.

Raises:

ValueError: If num is unspecified and cannot be inferred.

`tf.reverse_sequence(input, seq_lengths, seq_dim, batch_dim=None, name=None)`

Reverses variable length slices.

This op first slices input along the dimension batch_dim, and for each slice i, reverses the first seq_lengths[i] elements along the dimension seq_dim.

The elements of seq_lengths must obey seq_lengths[i] < input.dims[seq_dim], and seq_lengths must be a vector of length input.dims[batch_dim].

The output slice i along dimension batch_dim is then given by input slice i, with the first seq_lengths[i] slices along dimension seq_dim reversed.

For example:

# Given this:
batch_dim = 0
seq_dim = 1
input.dims = (4, 8, ...)
seq_lengths = [7, 2, 3, 5]

# then slices of input are reversed on seq_dim, but only up to seq_lengths:
output[0, 0:7, :, ...] = input[0, 7:0:-1, :, ...]
output[1, 0:2, :, ...] = input[1, 2:0:-1, :, ...]
output[2, 0:3, :, ...] = input[2, 3:0:-1, :, ...]
output[3, 0:5, :, ...] = input[3, 5:0:-1, :, ...]

# while entries past seq_lens are copied through:
output[0, 7:, :, ...] = input[0, 7:, :, ...]
output[1, 2:, :, ...] = input[1, 2:, :, ...]
output[2, 3:, :, ...] = input[2, 3:, :, ...]
output[3, 2:, :, ...] = input[3, 2:, :, ...]

In contrast, if:

# Given this:
batch_dim = 2
seq_dim = 0
input.dims = (8, ?, 4, ...)
seq_lengths = [7, 2, 3, 5]

# then slices of input are reversed on seq_dim, but only up to seq_lengths:
output[0:7, :, 0, :, ...] = input[7:0:-1, :, 0, :, ...]
output[0:2, :, 1, :, ...] = input[2:0:-1, :, 1, :, ...]
output[0:3, :, 2, :, ...] = input[3:0:-1, :, 2, :, ...]
output[0:5, :, 3, :, ...] = input[5:0:-1, :, 3, :, ...]

# while entries past seq_lens are copied through:
output[7:, :, 0, :, ...] = input[7:, :, 0, :, ...]
output[2:, :, 1, :, ...] = input[2:, :, 1, :, ...]
output[3:, :, 2, :, ...] = input[3:, :, 2, :, ...]
output[2:, :, 3, :, ...] = input[2:, :, 3, :, ...]

Args:

input: A Tensor. The input to reverse.
seq_lengths: A Tensor of type int64. 1-D with length input.dims(batch_dim) and max(seq_lengths) < input.dims(seq_dim)
seq_dim: An int. The dimension which is partially reversed.
batch_dim: An optional int. Defaults to 0. The dimension along which reversal is performed.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input. The partially reversed input. It has the same shape as input.

`tf.reverse(tensor, dims, name=None)`

Reverses specific dimensions of a tensor.

Given a tensor, and a bool tensor dims representing the dimensions of tensor, this operation reverses each dimension i of tensor where dims[i] is True.

tensor can have up to 8 dimensions. The number of dimensions of tensor must equal the number of elements in dims. In other words:

rank(tensor) = size(dims)

For example:

# tensor 't' is [[[[ 0,  1,  2,  3],
#                  [ 4,  5,  6,  7],
#                  [ 8,  9, 10, 11]],
#                 [[12, 13, 14, 15],
#                  [16, 17, 18, 19],
#                  [20, 21, 22, 23]]]]
# tensor 't' shape is [1, 2, 3, 4]

# 'dims' is [False, False, False, True]
reverse(t, dims) ==> [[[[ 3,  2,  1,  0],
                        [ 7,  6,  5,  4],
                        [ 11, 10, 9, 8]],
                       [[15, 14, 13, 12],
                        [19, 18, 17, 16],
                        [23, 22, 21, 20]]]]

# 'dims' is [False, True, False, False]
reverse(t, dims) ==> [[[[12, 13, 14, 15],
                        [16, 17, 18, 19],
                        [20, 21, 22, 23]
                       [[ 0,  1,  2,  3],
                        [ 4,  5,  6,  7],
                        [ 8,  9, 10, 11]]]]

# 'dims' is [False, False, True, False]
reverse(t, dims) ==> [[[[8, 9, 10, 11],
                        [4, 5, 6, 7],
                        [0, 1, 2, 3]]
                       [[20, 21, 22, 23],
                        [16, 17, 18, 19],
                        [12, 13, 14, 15]]]]

Args:

tensor: A Tensor. Must be one of the following types: uint8, int8, int32, bool, half, float32, float64. Up to 8-D.
dims: A Tensor of type bool. 1-D. The dimensions to reverse.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as tensor. The same shape as tensor.

`tf.transpose(a, perm=None, name='transpose')`

Transposes a. Permutes the dimensions according to perm.

The returned tensor's dimension i will correspond to the input dimension perm[i]. If perm is not given, it is set to (n-1...0), where n is the rank of the input tensor. Hence by default, this operation performs a regular matrix transpose on 2-D input Tensors.

For example:

# 'x' is [[1 2 3]
#         [4 5 6]]
tf.transpose(x) ==> [[1 4]
                     [2 5]
                     [3 6]]

# Equivalently
tf.transpose(x, perm=[1, 0]) ==> [[1 4]
                                  [2 5]
                                  [3 6]]

# 'perm' is more useful for n-dimensional tensors, for n > 2
# 'x' is   [[[1  2  3]
#            [4  5  6]]
#           [[7  8  9]
#            [10 11 12]]]
# Take the transpose of the matrices in dimension-0
tf.transpose(x, perm=[0, 2, 1]) ==> [[[1  4]
                                      [2  5]
                                      [3  6]]

                                     [[7 10]
                                      [8 11]
                                      [9 12]]]

Args:

a: A Tensor.
perm: A permutation of the dimensions of a.
name: A name for the operation (optional).

Returns:

A transposed Tensor.

`tf.extract_image_patches(images, padding, ksizes=None, strides=None, rates=None, name=None)`

Extract patches from images and puth them in the "depth" output dimension.

Args:

images: A Tensor. Must be one of the following types: float32, float64, int32, int64, uint8, int16, int8, uint16, half. 4-D Tensor with shape [batch, in_rows, in_cols, depth].

padding: A string from: "SAME", "VALID". The type of padding algorithm to use.

We specify the size-related attributes as:

   ksizes = [1, ksize_rows, ksize_cols, 1]
   strides = [1, strides_rows, strides_cols, 1]
   rates = [1, rates_rows, rates_cols, 1]

ksizes: An optional list of ints. Defaults to []. The size of the sliding window for each dimension of images.
strides: An optional list of ints. Defaults to []. 1-D of length 4. How far the centers of two consecutive patches are in the images. Must be: [1, stride_rows, stride_cols, 1].
rates: An optional list of ints. Defaults to []. 1-D of length 4. Must be: [1, rate_rows, rate_cols, 1]. This is the input stride, specifying how far two consecutive patch samples are in the input. Equivalent to extracting patches with patch_sizes_eff = patch_sizes + (patch_sizes - 1) * (rates - 1), followed by subsampling them spatially by a factor ofrates`.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as images. 4-D Tensor with shape [batch, out_rows, out_cols, ksize_rows * ksize_cols * depth] containing image patches with size ksize_rows x ksize_cols x depth vectorized in the "depth" dimension.

`tf.space_to_batch(input, paddings, block_size, name=None)`

SpaceToBatch for 4-D tensors of type T.

Zero-pads and then rearranges (permutes) blocks of spatial data into batch. More specifically, this op outputs a copy of the input tensor where values from the height and width dimensions are moved to the batch dimension. After the zero-padding, both height and width of the input must be divisible by the block size.

Args:

input: A Tensor. 4-D with shape [batch, height, width, depth].
paddings: A Tensor of type int32. 2-D tensor of non-negative integers with shape [2, 2]. It specifies the padding of the input with zeros across the spatial dimensions as follows:
```
   paddings = [[pad_top, pad_bottom], [pad_left, pad_right]]
```
The effective spatial dimensions of the zero-padded input tensor will be:
```
   height_pad = pad_top + height + pad_bottom
   width_pad = pad_left + width + pad_right
```
The attr block_size must be greater than one. It indicates the block size.
- Non-overlapping blocks of size block_size x block size in the height and width dimensions are rearranged into the batch dimension at each location.
- The batch of the output tensor is batch * block_size * block_size.
- Both height_pad and width_pad must be divisible by block_size.
  
  The shape of the output will be:
  
  [batchblock_sizeblock_size, height_pad/block_size, width_pad/block_size, depth]
block_size: An int.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input.

`tf.batch_to_space(input, crops, block_size, name=None)`

BatchToSpace for 4-D tensors of type T.

Rearranges (permutes) data from batch into blocks of spatial data, followed by cropping. This is the reverse transformation of SpaceToBatch. More specifically, this op outputs a copy of the input tensor where values from the batch dimension are moved in spatial blocks to the height and width dimensions, followed by cropping along the height and width dimensions.

Args:

input: A Tensor. 4-D tensor with shape [batch*block_size*block_size, height_pad/block_size, width_pad/block_size, depth]. Note that the batch size of the input tensor must be divisible by block_size * block_size.
crops: A Tensor of type int32. 2-D tensor of non-negative integers with shape [2, 2]. It specifies how many elements to crop from the intermediate result across the spatial dimensions as follows:
```
 crops = [[crop_top, crop_bottom], [crop_left, crop_right]]
```
block_size: An int.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input. 4-D with shape [batch, height, width, depth], where:

    height = height_pad - crop_top - crop_bottom
    width = width_pad - crop_left - crop_right

The attr block_size must be greater than one. It indicates the block size.

`tf.space_to_depth(input, block_size, name=None)`

SpaceToDepth for tensors of type T.

Rearranges blocks of spatial data, into depth. More specifically, this op outputs a copy of the input tensor where values from the height and width dimensions are moved to the depth dimension. The attr block_size indicates the input block size and how the data is moved.

Non-overlapping blocks of size block_size x block size are rearranged into depth at each location.
The depth of the output tensor is input_depth * block_size * block_size.
The input tensor's height and width must be divisible by block_size.

That is, assuming the input is in the shape: [batch, height, width, depth], the shape of the output will be: [batch, height/block_size, width/block_size, depth*block_size*block_size]

This operation requires that the input tensor be of rank 4, and that block_size be >=1 and a divisor of both the input height and width.

This operation is useful for resizing the activations between convolutions (but keeping all data), e.g. instead of pooling. It is also useful for training purely convolutional models.

For example, given this input of shape [1, 2, 2, 1], and block_size of 2:

x = [[[[1], [2]],
      [[3], [4]]]]

This operation will output a tensor of shape [1, 1, 1, 4]:

[[[[1, 2, 3, 4]]]]

Here, the input has a batch of 1 and each batch element has shape [2, 2, 1], the corresponding output will have a single element (i.e. width and height are both 1) and will have a depth of 4 channels (1 block_size block_size). The output element shape is [1, 1, 4].

For an input tensor with larger depth, here of shape [1, 2, 2, 3], e.g.

x = [[[[1, 2, 3], [4, 5, 6]],
      [[7, 8, 9], [10, 11, 12]]]]

This operation, for block_size of 2, will return the following tensor of shape [1, 1, 1, 12]

[[[[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]]]]

Similarly, for the following input of shape [1 4 4 1], and a block size of 2:

x = [[[[1],   [2],  [5],  [6]],
      [[3],   [4],  [7],  [8]],
      [[9],  [10], [13],  [14]],
      [[11], [12], [15],  [16]]]]

the operator will return the following tensor of shape [1 2 2 4]:

x = [[[[1, 2, 3, 4],
       [5, 6, 7, 8]],
      [[9, 10, 11, 12],
       [13, 14, 15, 16]]]]

Args:

input: A Tensor.
block_size: An int. The size of the spatial block.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input.

`tf.depth_to_space(input, block_size, name=None)`

DepthToSpace for tensors of type T.

Rearranges data from depth into blocks of spatial data. This is the reverse transformation of SpaceToDepth. More specifically, this op outputs a copy of the input tensor where values from the depth dimension are moved in spatial blocks to the height and width dimensions. The attr block_size indicates the input block size and how the data is moved.

Chunks of data of size block_size * block_size from depth are rearranged into non-overlapping blocks of size block_size x block_size
The width the output tensor is input_depth * block_size, whereas the height is input_height * block_size.
The depth of the input tensor must be divisible by block_size * block_size.

That is, assuming the input is in the shape: [batch, height, width, depth], the shape of the output will be: [batch, height*block_size, width*block_size, depth/(block_size*block_size)]

This operation requires that the input tensor be of rank 4, and that block_size be >=1 and that block_size * block_size be a divisor of the input depth.

This operation is useful for resizing the activations between convolutions (but keeping all data), e.g. instead of pooling. It is also useful for training purely convolutional models.

For example, given this input of shape [1, 1, 1, 4], and a block size of 2:

x = [[[[1, 2, 3, 4]]]]

This operation will output a tensor of shape [1, 2, 2, 1]:

   [[[[1], [2]],
     [[3], [4]]]]

Here, the input has a batch of 1 and each batch element has shape [1, 1, 4], the corresponding output will have 2x2 elements and will have a depth of 1 channel (1 = 4 / (block_size * block_size)). The output element shape is [2, 2, 1].

For an input tensor with larger depth, here of shape [1, 1, 1, 12], e.g.

x = [[[[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]]]]

This operation, for block size of 2, will return the following tensor of shape [1, 2, 2, 3]

   [[[[1, 2, 3], [4, 5, 6]],
     [[7, 8, 9], [10, 11, 12]]]]

Similarly, for the following input of shape [1 2 2 4], and a block size of 2:

x =  [[[[1, 2, 3, 4],
       [5, 6, 7, 8]],
      [[9, 10, 11, 12],
       [13, 14, 15, 16]]]]

the operator will return the following tensor of shape [1 4 4 1]:

x = [[ [1],   [2],  [5],  [6]],
     [ [3],   [4],  [7],  [8]],
     [ [9],  [10], [13],  [14]],
     [ [11], [12], [15],  [16]]]

Args:

input: A Tensor.
block_size: An int. The size of the spatial block, same as in Space2Depth.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as input.

`tf.gather(params, indices, validate_indices=None, name=None)`

Gather slices from params according to indices.

indices must be an integer tensor of any dimension (usually 0-D or 1-D). Produces an output tensor with shape indices.shape + params.shape[1:] where:

# Scalar indices
output[:, ..., :] = params[indices, :, ... :]

# Vector indices
output[i, :, ..., :] = params[indices[i], :, ... :]

# Higher rank indices
output[i, ..., j, :, ... :] = params[indices[i, ..., j], :, ..., :]

If indices is a permutation and len(indices) == params.shape[0] then this operation will permute params accordingly.

Args:

params: A Tensor.
indices: A Tensor. Must be one of the following types: int32, int64.
validate_indices: An optional bool. Defaults to True.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as params.

`tf.gather_nd(params, indices, name=None)`

Gather values from params according to indices.

indices must be integer tensor, containing indices into params. It must be shape [d_0, ..., d_N, R] where R is the rank of params. The innermost dimension of indices (with length R) corresponds to the indices of params.

Produces an output tensor with shape [d_0, ..., d_{n-1}] where:

output[i, j, k, ...] = params[indices[i, j, k, ..., :]]

e.g. for indices a matrix:

output[i] = params[indices[i, :]]

Args:

params: A Tensor. R-D. The tensor from which to gather values.
indices: A Tensor. Must be one of the following types: int32, int64. (N+1)-D. Index tensor having shape [d_0, ..., d_N, R].
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as params. N-D. Values from params gathered from indices given by indices.

`tf.dynamic_partition(data, partitions, num_partitions, name=None)`

Partitions data into num_partitions tensors using indices from partitions.

For each index tuple js of size partitions.ndim, the slice data[js, ...] becomes part of outputs[partitions[js]]. The slices with partitions[js] = i are placed in outputs[i] in lexicographic order of js, and the first dimension of outputs[i] is the number of entries in partitions equal to i. In detail,

outputs[i].shape = [sum(partitions == i)] + data.shape[partitions.ndim:]

outputs[i] = pack([data[js, ...] for js if partitions[js] == i])

data.shape must start with partitions.shape.

For example:

# Scalar partitions
partitions = 1
num_partitions = 2
data = [10, 20]
outputs[0] = []  # Empty with shape [0, 2]
outputs[1] = [[10, 20]]

# Vector partitions
partitions = [0, 0, 1, 1, 0]
num_partitions = 2
data = [10, 20, 30, 40, 50]
outputs[0] = [10, 20, 50]
outputs[1] = [30, 40]

Args:

data: A Tensor.
partitions: A Tensor of type int32. Any shape. Indices in the range [0, num_partitions).
num_partitions: An int that is >= 1. The number of partitions to output.
name: A name for the operation (optional).

Returns:

A list of num_partitions Tensor objects of the same type as data.

`tf.dynamic_stitch(indices, data, name=None)`

Interleave the values from the data tensors into a single tensor.

Builds a merged tensor such that

merged[indices[m][i, ..., j], ...] = data[m][i, ..., j, ...]

For example, if each indices[m] is scalar or vector, we have

# Scalar indices
merged[indices[m], ...] = data[m][...]

# Vector indices
merged[indices[m][i], ...] = data[m][i, ...]

Each data[i].shape must start with the corresponding indices[i].shape, and the rest of data[i].shape must be constant w.r.t. i. That is, we must have data[i].shape = indices[i].shape + constant. In terms of this constant, the output shape is

merged.shape = [max(indices)] + constant

Values are merged in order, so if an index appears in both indices[m][i] and indices[n][j] for (m,i) < (n,j) the slice data[n][j] will appear in the merged result.

For example:

indices[0] = 6
indices[1] = [4, 1]
indices[2] = [[5, 2], [0, 3]]
data[0] = [61, 62]
data[1] = [[41, 42], [11, 12]]
data[2] = [[[51, 52], [21, 22]], [[1, 2], [31, 32]]]
merged = [[1, 2], [11, 12], [21, 22], [31, 32], [41, 42],
          [51, 52], [61, 62]]

Args:

indices: A list of at least 2 Tensor objects of type int32.
data: A list with the same number of Tensor objects as indices of Tensor objects of the same type.
name: A name for the operation (optional).

Returns:

A Tensor. Has the same type as data.

`tf.boolean_mask(tensor, mask, name='boolean_mask')`

Apply boolean mask to tensor. Numpy equivalent is tensor[mask].

# 1-D example
tensor = [0, 1, 2, 3]
mask = [True, False, True, False]
boolean_mask(tensor, mask) ==> [0, 2]

In general, 0 < dim(mask) = K <= dim(tensor), and mask's shape must match the first K dimensions of tensor's shape. We then have: boolean_mask(tensor, mask)[i, j1,...,jd] = tensor[i1,...,iK,j1,...,jd] where (i1,...,iK) is the ith True entry of mask (row-major order).

Args:

tensor: N-D tensor.
mask: K-D boolean tensor, K <= N and K must be known statically.
name: A name for this operation (optional).

Returns:

Tensor populated by entries in tensor corresponding to True values in mask.

Raises:

ValueError: If shapes do not conform.

Examples:

# 2-D example
tensor = [[1, 2], [3, 4], [5, 6]]
mask = [True, False, True]
boolean_mask(tensor, mask) ==> [[1, 2], [5, 6]]

`tf.one_hot(indices, depth, on_value=None, off_value=None, axis=None, dtype=None, name=None)`

Returns a one-hot tensor.

The locations represented by indices in indices take value on_value, while all other locations take value off_value.

on_value and off_value must have matching data types. If dtype is also provided, they must be the same data type as specified by dtype.

If on_value is not provided, it will default to the value 1 with type dtype

If off_value is not provided, it will default to the value 0 with type dtype

If the input indices is rank N, the output will have rank N+1. The new axis is created at dimension axis (default: the new axis is appended at the end).

If indices is a scalar the output shape will be a vector of length depth

If indices is a vector of length features, the output shape will be:

  features x depth if axis == -1
  depth x features if axis == 0

If indices is a matrix (batch) with shape [batch, features], the output shape will be:

  batch x features x depth if axis == -1
  batch x depth x features if axis == 1
  depth x batch x features if axis == 0

If dtype is not provided, it will attempt to assume the data type of on_value or off_value, if one or both are passed in. If none of on_value, off_value, or dtype are provided, dtype will default to the value tf.float32

Note: If a non-numeric data type output is desired (tf.string, tf.bool, etc.), both on_value and off_value must be provided to one_hot

Examples

Suppose that

  indices = [0, 2, -1, 1]
  depth = 3
  on_value = 5.0
  off_value = 0.0
  axis = -1

Then output is [4 x 3]:

  output =
  [5.0 0.0 0.0]  // one_hot(0)
  [0.0 0.0 5.0]  // one_hot(2)
  [0.0 0.0 0.0]  // one_hot(-1)
  [0.0 5.0 0.0]  // one_hot(1)

Suppose that

  indices = [[0, 2], [1, -1]]
  depth = 3
  on_value = 1.0
  off_value = 0.0
  axis = -1

Then output is [2 x 2 x 3]:

  output =
  [
    [1.0, 0.0, 0.0]  // one_hot(0)
    [0.0, 0.0, 1.0]  // one_hot(2)
  ][
    [0.0, 1.0, 0.0]  // one_hot(1)
    [0.0, 0.0, 0.0]  // one_hot(-1)
  ]

Using default values for on_value and off_value:

  indices = [0, 1, 2]
  depth = 3

The output will be

  output =
  [[1., 0., 0.],
   [0., 1., 0.],
   [0., 0., 1.]]

Args:

indices: A Tensor of indices.
depth: A scalar defining the depth of the one hot dimension.
on_value: A scalar defining the value to fill in output when indices[j] = i. (default: 1)
off_value: A scalar defining the value to fill in output when indices[j] != i. (default: 0)
axis: The axis to fill (default: -1, a new inner-most axis).
dtype: The data type of the output tensor.

Returns:

output: The one-hot tensor.

Raises:

TypeError: If dtype of either on_value or off_value don't match dtype
TypeError: If dtype of on_value and off_value don't match one another

Other Functions and Classes

`tf.bitcast(input, type, name=None)`

Bitcasts a tensor from one type to another without copying data.

Given a tensor input, this operation returns a tensor that has the same buffer data as input with datatype type.

If the input datatype T is larger than the output datatype type then the shape changes from [...] to [..., sizeof(T)/sizeof(type)].

If T is smaller than type, the operator requires that the rightmost dimension be equal to sizeof(type)/sizeof(T). The shape then goes from [..., sizeof(type)/sizeof(T)] to [...].

Args:

input: A Tensor. Must be one of the following types: float32, float64, int64, int32, uint8, uint16, int16, int8, complex64, complex128, qint8, quint8, qint32, half.
type: A tf.DType from: tf.float32, tf.float64, tf.int64, tf.int32, tf.uint8, tf.uint16, tf.int16, tf.int8, tf.complex64, tf.complex128, tf.qint8, tf.quint8, tf.qint32, tf.half.
name: A name for the operation (optional).

Returns:

A Tensor of type type.

`tf.shape_n(input, name=None)`

Returns shape of tensors.

This operation returns N 1-D integer tensors representing shape of input[i]s.

Args:

input: A list of at least 1 Tensor objects of the same type.
name: A name for the operation (optional).

Returns:

A list with the same number of Tensor objects as input of Tensor objects of type int32.

`tf.unique_with_counts(x, name=None)`

Finds unique elements in a 1-D tensor.

This operation returns a tensor y containing all of the unique elements of x sorted in the same order that they occur in x. This operation also returns a tensor idx the same size as x that contains the index of each value of x in the unique output y. Finally, it returns a third tensor count that contains the count of each element of y in x. In other words:

y[idx[i]] = x[i] for i in [0, 1,...,rank(x) - 1]

For example:

# tensor 'x' is [1, 1, 2, 4, 4, 4, 7, 8, 8]
y, idx, count = unique_with_counts(x)
y ==> [1, 2, 4, 7, 8]
idx ==> [0, 0, 1, 2, 2, 2, 3, 4, 4]
count ==> [2, 1, 3, 1, 2]

Args:

x: A Tensor. 1-D.
name: A name for the operation (optional).

Returns:

A tuple of Tensor objects (y, idx, count).

y: A Tensor. Has the same type as x. 1-D.
idx: A Tensor of type int32. 1-D.
count: A Tensor of type int32. 1-D.