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.. regarding copyright ownership.  The ASF licenses this file
.. to you under the Apache License, Version 2.0 (the
.. "License"); you may not use this file except in compliance
.. with the License.  You may obtain a copy of the License at

..   http://www.apache.org/licenses/LICENSE-2.0

.. Unless required by applicable law or agreed to in writing,
.. software distributed under the License is distributed on an
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.. KIND, either express or implied.  See the License for the
.. specific language governing permissions and limitations
.. under the License.

Other Data Structures
=====================

Our `Flatbuffers protocol definition files`_ have metadata for some other data
structures defined to allow other kinds of applications to take advantage of
common interprocess communication machinery. These data structures are not
considered to be part of the columnar format.

An Arrow columnar implementation is not required to implement these
types.

Tensor (Multi-dimensional Array)
--------------------------------

The ``Tensor`` message types provides a way to write a
multidimensional array of fixed-size values (such as a NumPy ndarray).

When writing a standalone encapsulated tensor message, we use the
encapsulated IPC format defined in the :ref:`Columnar Specification
<format_columnar>`, but additionally align the starting offset of the
tensor body to be a multiple of 64 bytes: ::

    <metadata prefix and metadata>
    <PADDING>
    <tensor body>

Sparse Tensor
-------------

``SparseTensor`` represents a multidimensional array whose elements
are generally almost all zeros.

When writing a standalone encapsulated sparse tensor message, we use
the encapsulated IPC format defined in the :ref:`Columnar Specification
<format_columnar>`, but additionally align the starting offsets of the
sparse index and the sparse tensor body (if writing to a shared memory
region) to be multiples of 64 bytes: ::

    <metadata prefix and metadata>
    <PADDING>
    <sparse index>
    <PADDING>
    <sparse tensor body>

The contents of the sparse tensor index depends on what kind of sparse
format is used.

.. _Flatbuffers protocol definition files: https://github.com/apache/arrow/tree/main/format
