.. _op_ai_onnx_Concat:

Concat
======

- **Domain**: ``ai.onnx``
- **Since version**: 13

Concatenate a list of tensors into a single tensor. All input tensors must have the same shape, except for the dimension size of the axis to concatenate on.

**Inputs**

- **inputs** (*T*): List of tensors for concatenation

**Outputs**

- **concat_result** (*T*): Concatenated tensor

**Type Constraints**

- **T**: Constrain output types to any tensor type.
  Allowed types: tensor(bfloat16), tensor(bool), tensor(complex128), tensor(complex64), tensor(double), tensor(float), tensor(float16), tensor(int16), tensor(int32), tensor(int64), tensor(int8), tensor(string), tensor(uint16), tensor(uint32), tensor(uint64), tensor(uint8).

Examples
--------

**test_cc_concat_2d_axis_0**

.. code-block:: text

    Attributes:
      axis = 0

.. code-block:: text

    Inputs:
      x0: shape=(2, 2), dtype=float32
        [[1., 2.],
         [3., 4.]]
      x1: shape=(2, 2), dtype=float32
        [[5., 6.],
         [7., 8.]]

    Outputs:
      y: shape=(4, 2), dtype=float32
        [[1., 2.],
         [3., 4.],
         [5., 6.],
         [7., 8.]]

**test_cc_concat_2d_axis_negative**

.. code-block:: text

    Attributes:
      axis = -1

.. code-block:: text

    Inputs:
      x0: shape=(2, 3), dtype=float32
        [[1., 2., 3.],
         [4., 5., 6.]]
      x1: shape=(2, 3), dtype=float32
        [[10., 20., 30.],
         [40., 50., 60.]]

    Outputs:
      y: shape=(2, 6), dtype=float32
        [[ 1.,  2.,  3., 10., 20., 30.],
         [ 4.,  5.,  6., 40., 50., 60.]]

Differences with previous version (11)
--------------------------------------

**SchemaDiff**: ``Concat`` (domain ``'ai.onnx'``)

* old version: 11
* new version: 13
* breaking: no

**Type constraints:**

* changed 'T': added types: ['tensor(bfloat16)']

Version History
---------------

- :doc:`Version 11 <Concat-11>`
- :doc:`Version 4 <Concat-4>`
- :doc:`Version 1 <Concat-1>`