Programming interface#

All types and functions in this section are declared in the oneapi::dal::spmd::preview namespace and are available via inclusion of the header file from specified backend.


A base implementation of the communicator concept. The communicator type and all of its subtypes are reference-counted:

  1. The instance stores a pointer to the communicator implementation that holds all property values and data.

  2. The reference count indicates how many communicator objects refer to the same implementation.

  3. The communicator increments the reference count for it to be equal to the number of communicator objects sharing the same implementation.

  4. The communicator decrements the reference count when the communicator goes out of the scope. If the reference count is zero, the communicator frees its implementation.

USM and non-USM memory usage#

There are two types of memory access:

  • USM memory access (both USM and non-USM pointers can be used)

  • Host, or non-USM, memory access (only non-USM pointers can be used)

Use one of the following tags to select a memory access type:


Assumes only non-USM pointers are used for a collective operation.


Both USM and non-USM can be used. Pointer type is controlled by the use of sycl::queue object as a first parameter for collective operations. The use of sycl::queue object is obligatory for USM pointers.


Request is an object to control asynchronous communication.

Reducion operations#

The following reduction operations are supported:

  • Max

  • Min

  • Sum