# Sparse Tensor Representation

TensorFlow supports a SparseTensor representation for data that is sparse in multiple dimensions. Contrast this representation with IndexedSlices, which is efficient for representing tensors that are sparse in their first dimension, and dense along all other dimensions.

### class tf.SparseTensor

Represents a sparse tensor.

TensorFlow represents a sparse tensor as three separate dense tensors: indices, values, and shape. In Python, the three tensors are collected into a SparseTensor class for ease of use. If you have separate indices, values, and shape tensors, wrap them in a SparseTensor object before passing to the ops below.

Concretely, the sparse tensor SparseTensor(indices, values, shape) is

• indices: A 2-D int64 tensor of shape [N, ndims].
• values: A 1-D tensor of any type and shape [N].
• shape: A 1-D int64 tensor of shape [ndims].

where N and ndims are the number of values, and number of dimensions in the SparseTensor respectively.

The corresponding dense tensor satisfies

dense.shape = shape
dense[tuple(indices[i])] = values[i]


By convention, indices should be sorted in row-major order (or equivalently lexicographic order on the tuples indices[i]). This is not enforced when SparseTensor objects are constructed, but most ops assume correct ordering. If the ordering of sparse tensor st is wrong, a fixed version can be obtained by calling tf.sparse_reorder(st).

Example: The sparse tensor

SparseTensor(indices=[[0, 0], [1, 2]], values=[1, 2], shape=[3, 4])


represents the dense tensor

[[1, 0, 0, 0]
[0, 0, 2, 0]
[0, 0, 0, 0]]


#### tf.SparseTensor.__init__(indices, values, shape) {:#SparseTensor.init}

Creates a SparseTensor.

##### Args:
• indices: A 2-D int64 tensor of shape [N, ndims].
• values: A 1-D tensor of any type and shape [N].
• shape: A 1-D int64 tensor of shape [ndims].
##### Returns:

A SparseTensor

#### tf.SparseTensor.indices

The indices of non-zero values in the represented dense tensor.

##### Returns:

A 2-D Tensor of int64 with shape [N, ndims], where N is the number of non-zero values in the tensor, and ndims is the rank.

#### tf.SparseTensor.values

The non-zero values in the represented dense tensor.

##### Returns:

A 1-D Tensor of any data type.

#### tf.SparseTensor.shape

A 1-D Tensor of int64 representing the shape of the dense tensor.

#### tf.SparseTensor.dtype

The DType of elements in this tensor.

#### tf.SparseTensor.op

The Operation that produces values as an output.

#### tf.SparseTensor.graph

The Graph that contains the index, value, and shape tensors.

#### tf.SparseTensor.eval(feed_dict=None, session=None)

Evaluates this sparse tensor in a Session.

Calling this method will execute all preceding operations that produce the inputs needed for the operation that produces this tensor.

N.B. Before invoking SparseTensor.eval(), its graph must have been launched in a session, and either a default session must be available, or session must be specified explicitly.

##### Args:
• feed_dict: A dictionary that maps Tensor objects to feed values. See Session.run() for a description of the valid feed values.
• session: (Optional.) The Session to be used to evaluate this sparse tensor. If none, the default session will be used.
##### Returns:

A SparseTensorValue object.

### class tf.SparseTensorValue

SparseTensorValue(indices, values, shape)

#### tf.SparseTensorValue.indices

Alias for field number 0

#### tf.SparseTensorValue.shape

Alias for field number 2

#### tf.SparseTensorValue.values

Alias for field number 1