.. index:: pair: page; Accumulation Mode
.. _doxid-dev_guide_attributes_accumulation_mode:

Accumulation Mode
=================

Some applications can benefit from using lower precision accumulators to speed up computations without causing noticeable impacts on accuracy.

The default numerical behavior of oneDNN (described in :ref:`Data Types <doxid-dev_guide_data_types>`) can be altered to allow the use of low precision accumulators. When passed to a primitive creation, the :ref:`dnnl::accumulation_mode <doxid-group__dnnl__api__accumulation__mode_1gad6b8b3ca2e61b8a9703227f4d58ac215>` primitive attribute specifies which datatype can be used for accumulation purposes for that given primitive.

The :ref:`dnnl::accumulation_mode <doxid-group__dnnl__api__accumulation__mode_1gad6b8b3ca2e61b8a9703227f4d58ac215>` primitive attribute accepts:

* ``strict`` (default): For floating-point primitives (as defined in :ref:`Data Types <doxid-dev_guide_data_types>`), the default accumulation datatype is ``f32`` (or ``f64`` for ``f64`` primitives). For integral primitives (as defined in :ref:`Data Types <doxid-dev_guide_data_types>`), the default accumulation datatype is ``s32``.

* ``relaxed`` : Same as strict except some partial accumulators can be rounded to the src/dst datatype in memory.

* ``any`` : Uses the fastest implementation available with one of the src/dst datatypes or a higher precision accumulation datatype.

* ``f32``, ``f16`` and ``s32`` : Uses the specified accumulation datatype.