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.. _op_ai_onnx_GatherElements-11:

GatherElements - version 11
===========================

This page documents version **11** of operator **GatherElements**. See :doc:`GatherElements` for the latest version (since version 13).

- **Domain**: ``ai.onnx``
- **Since version**: 11

GatherElements takes two inputs ``data`` and ``indices`` of the same rank r >= 1
and an optional attribute ``axis`` that identifies an axis of ``data``
(by default, the outer-most axis, that is axis 0). It is an indexing operation
that produces its output by indexing into the input data tensor at index
positions determined by elements of the ``indices`` tensor.
Its output shape is the same as the shape of ``indices`` and consists of one value
(gathered from the ``data``) for each element in ``indices``.

For instance, in the 3-D case (r = 3), the output produced is determined
by the following equations:

.. code-block::

      out[i][j][k] = input[index[i][j][k]][j][k] if axis = 0,
      out[i][j][k] = input[i][index[i][j][k]][k] if axis = 1,
      out[i][j][k] = input[i][j][index[i][j][k]] if axis = 2,


This operator is also the inverse of ScatterElements. It is similar to Torch's gather operation.

Example 1:

.. code-block::

      data = [
          [1, 2],
          [3, 4],
      ]
      indices = [
          [0, 0],
          [1, 0],
      ]
      axis = 1
      output = [
          [
            [1, 1],
            [4, 3],
          ],
      ]

Example 2:

.. code-block::

      data = [
          [1, 2, 3],
          [4, 5, 6],
          [7, 8, 9],
      ]
      indices = [
          [1, 2, 0],
          [2, 0, 0],
      ]
      axis = 0
      output = [
          [
            [4, 8, 3],
            [7, 2, 3],
          ],
      ]


**Inputs**

- **data** (*T*): Tensor of rank r >= 1.
- **indices** (*Tind*): Tensor of int32/int64 indices, with the same rank r as the input. All index values are expected to be within bounds [-s, s-1] along axis of size s. It is an error if any of the index values are out of bounds.

**Outputs**

- **output** (*T*): Tensor of the same shape as indices.

**Attributes**

- **axis** (*int*): Which axis to gather on. Negative value means counting dimensions from the back. Accepted range is [-r, r-1] where r = rank(data).

**Type Constraints**

- **T**: Constrain input and output types to any tensor type.
  Allowed types: 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).
- **Tind**: Constrain indices to integer types
  Allowed types: tensor(int32), tensor(int64).