Sum

API Reference

General

The sum primitive sums \(N\) tensors (the variable names follow the standard Naming Conventions):

\[ \dst(\overline{x}) = \sum\limits_{i = 1}^{N} scales(i) \cdot \src_i(\overline{x}) \]

The sum primitive does not have a notion of forward or backward propagations. The backward propagation for the sum 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
\(\src\)	DNNL_ARG_MULTIPLE_SRC
\(\dst\)	DNNL_ARG_DST

Implementation Details

General Notes

• The \(\dst\) memory format can be either specified by a user or derived the most appropriate one by the primitive. The recommended way is to allow the primitive to choose the appropriate format.
• The sum primitive requires all source and destination tensors to have the same shape. Implicit broadcasting is not supported.

Post-ops and Attributes

The sum primitive does not support any post-ops or attributes.

Data Types Support

The sum primitive supports arbitrary data types for source and destination tensors according to the Data Types page.

Data Representation

Sources, Destination

The sum primitive works with arbitrary data tensors. There is no special meaning associated with any logical dimensions.

Implementation Limitations

1. No primitive specific limitations. Refer to Data Types for limitations related to data types support.

Performance Tips

• Whenever possible do not specify the destination memory format so that the primitive is able to choose the most appropriate one.
• The sum primitive is highly optimized for the cases when all source tensors have same memory format and data type matches the destination tensor data type. For other cases more general but slower code is working. Consider reordering sources to the same data format before the sum primitive.

Examples

Engine	Name	Com
CPU/GPU	Sum Primitive Example	This C++ API example demonstrates how to create and execute a Sum primitive. Key optimizations included in this example: Identical memory formats for source (src) and destination (dst) tensors.