.. SPDX-FileCopyrightText: 2019-2020 Intel Corporation .. .. SPDX-License-Identifier: CC-BY-4.0 .. default-domain:: cpp .. include:: ../replacements.inc.rst ###### Concat ###### A primitive to concatenate data by arbitrary dimension. .. TODO this is confusing. Document what ou and in are. Why do we need C at all? The concat primitive concatenates :math:`N` tensors over ``concat_dimension`` (here denoted as :math:`C`), and is defined as .. math:: \dst(\overline{ou}, c, \overline{in}) = \src_i(\overline{ou}, c', \overline{in}), where - :math:`c = C_1 + \ldots + C_{i-1} + c'`, - :math:`\overline{ou}` is the outermost indices (to the left from concat axis), - :math:`\overline{in}` is the innermost indices (to the right from concat axis), and Variable names follow the standard :ref:`conventions-label`. ******************** Forward and Backward ******************** The concat primitive does not have a notion of forward or backward propagations. The backward propagation for the concatenation operation is simply an identity operation. ******************* Execution Arguments ******************* When executed, the inputs and outputs should be mapped to an execution argument index as specified by the following table. ====================== ======================== Primitive input/output Execution argument index ====================== ======================== :math:`\src` |DNNL_ARG_MULTIPLE_SRC| :math:`\dst` |DNNL_ARG_DST| ====================== ======================== ***************** Operation Details ***************** 1. The :math:`\dst` memory format can be either specified by a user or derived by the primitive. The recommended way is to allow the primitive to choose the most appropriate format. 2. The concat primitive requires all source and destination tensors to have the same shape except for the ``concat_dimension``. The destination dimension for the ``concat_dimension`` must be equal to the sum of the ``concat_dimension`` dimensions of the sources (i.e. :math:`C = \sum_i C_i`). Implicit broadcasting is not supported. ****************** Data Types Support ****************** The concat primitive supports arbitrary data types for source and destination tensors. However, it is required that all source tensors are of the same data type (but not necessarily matching the data type of the destination tensor). ******************* Data Representation ******************* The concat primitive does not assign any special meaning associated with any logical dimensions. *********************** Post-ops and Attributes *********************** The concat primitive does not support any post-ops or attributes. *** API *** .. doxygenstruct:: dnnl::concat :project: oneDNN :members: .. vim: ts=3 sw=3 et spell spelllang=en