.. _op_ai_onnx_If:

If
==

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

If conditional

**Inputs**

- **cond** (*B*): Condition for the if. The tensor must contain a single element.

**Outputs**

- **outputs** (*V*): Values that are live-out to the enclosing scope. The return values in the ``then_branch`` and ``else_branch`` must be of the same data type. The ``then_branch`` and ``else_branch`` may produce tensors with the same element type and different shapes. If corresponding outputs from the then-branch and the else-branch have static shapes S1 and S2, then the shape of the corresponding output variable of the if-node (if present) must be compatible with both S1 and S2 as it represents the union of both possible shapes.For example, if in a model file, the first output of ``then_branch`` is typed float tensor with shape [2] and the first output of ``else_branch`` is another float tensor with shape [3], If's first output should have (a) no shape set, or (b) a shape of rank 1 with neither ``dim_value`` nor ``dim_param`` set, or (c) a shape of rank 1 with a unique ``dim_param``. In contrast, the first output cannot have the shape [2] since [2] and [3] are not compatible.

**Type Constraints**

- **V**: All Tensor and Sequence types
  Allowed types: seq(tensor(bool)), seq(tensor(complex128)), seq(tensor(complex64)), seq(tensor(double)), seq(tensor(float)), seq(tensor(float16)), seq(tensor(int16)), seq(tensor(int32)), seq(tensor(int64)), seq(tensor(int8)), seq(tensor(string)), seq(tensor(uint16)), seq(tensor(uint32)), seq(tensor(uint64)), seq(tensor(uint8)), 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).
- **B**: Only bool
  Allowed types: tensor(bool).

Examples
--------

**test_cc_if**

.. code-block:: text

    Attributes:
      then_branch = <subgraph>
      else_branch = <subgraph>

.. code-block:: text

    Inputs:
      cond: shape=(), dtype=bool
        True

    Outputs:
      res: shape=(2,), dtype=float32
        [1., 2.]

**test_cc_if_else**

.. code-block:: text

    Attributes:
      then_branch = <subgraph>
      else_branch = <subgraph>

.. code-block:: text

    Inputs:
      cond: shape=(), dtype=bool
        False

    Outputs:
      res: shape=(2,), dtype=float32
        [3., 4.]

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

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

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

**Type constraints:**

* changed 'V': added types: ['seq(tensor(bool))', 'seq(tensor(complex128))', 'seq(tensor(complex64))', 'seq(tensor(double))', 'seq(tensor(float))', 'seq(tensor(float16))', 'seq(tensor(int16))', 'seq(tensor(int32))', 'seq(tensor(int64))', 'seq(tensor(int8))', 'seq(tensor(string))', 'seq(tensor(uint16))', 'seq(tensor(uint32))', 'seq(tensor(uint64))', 'seq(tensor(uint8))']

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

- :doc:`Version 11 <If-11>`
- :doc:`Version 1 <If-1>`