.. _op_ai_onnx_NonZero:

NonZero
=======

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

Returns the indices of the elements that are non-zero
(in row-major order - by dimension).
NonZero behaves similar to numpy.nonzero:
https://docs.scipy.org/doc/numpy/reference/generated/numpy.nonzero.html,
but for scalar input, NonZero produces output shape (0, N) instead of (1, N), which is different from Numpy's behavior.

**Inputs**

- **X** (*T*): input

**Outputs**

- **Y** (*tensor(int64)*): output

**Type Constraints**

- **T**: Constrain to all tensor types.
  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_nonzero_1d**

.. code-block:: text

    Node:
      NonZero(X) -> (Y)

.. code-block:: text

    Inputs:
      X: shape=(5,), dtype=float32
        [ 0.,  1.,  0., -1.,  2.]

    Outputs:
      Y: shape=(1, 3), dtype=int64
        [[1, 3, 4]]

**test_cc_nonzero_2d**

.. code-block:: text

    Node:
      NonZero(X) -> (Y)

.. code-block:: text

    Inputs:
      X: shape=(2, 2), dtype=float32
        [[1., 0.],
         [1., 1.]]

    Outputs:
      Y: shape=(2, 3), dtype=int64
        [[0, 1, 1],
         [0, 0, 1]]

**test_cc_nonzero_bool**

.. code-block:: text

    Node:
      NonZero(X) -> (Y)

.. code-block:: text

    Inputs:
      X: shape=(2, 3), dtype=bool
        [[ True, False,  True],
         [False,  True, False]]

    Outputs:
      Y: shape=(2, 3), dtype=int64
        [[0, 0, 1],
         [0, 2, 1]]

**test_cc_nonzero_example**

.. code-block:: text

    Node:
      NonZero(condition) -> (result)

.. code-block:: text

    Inputs:
      condition: shape=(2, 2), dtype=bool
        [[ True, False],
         [ True,  True]]

    Outputs:
      result: shape=(2, 3), dtype=int64
        [[0, 1, 1],
         [0, 0, 1]]

**test_cc_nonzero_int64**

.. code-block:: text

    Node:
      NonZero(X) -> (Y)

.. code-block:: text

    Inputs:
      X: shape=(2, 3), dtype=int64
        [[0, 1, 2],
         [0, 0, 3]]

    Outputs:
      Y: shape=(2, 3), dtype=int64
        [[0, 0, 1],
         [1, 2, 2]]

Differences with previous version (9)
-------------------------------------

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

* old version: 9
* new version: 13
* breaking: no

**Type constraints:**

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

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

- :doc:`Version 9 <NonZero-9>`