Introduction#
What is Intel® SHMEM?#
Intel® SHMEM is a C++ software library interface that enables OpenSHMEM communication for applications using Intel® Data Center GPU Max Series devices with device kernels implemented in SYCL. Intel® SHMEM includes both host-initiated operations as in OpenSHMEM, and new device-initiated operations callable directly from GPU kernels. When available, Intel® SHMEM optimizes performance for GPUs connected by Intel® \(\text{X}^e\) Link fabric. For multi-node communication, Intel® SHMEM enables GPU-initiated operations by passing requests to the host CPU, which transfers the data through the network fabric to another GPU’s memory.
The original OpenSHMEM specification, described in the “What is OpenSHMEM?” section, establishes a programming and memory model that is most suitable for host-driven (CPU) communication. The Intel® SHMEM APIs are based on the original OpenSHMEM interfaces, but are augmented to support device-driven communication across a network of compute accelerators, as exposed by the SYCL programming model. Supporting OpenSHMEM communication between SYCL host and device memories requires subtle modifications to the original OpenSHMEM interfaces, memory model, and execution model. The Intel® SHMEM APIs are defined in the context of this adjusted memory and execution model, which is described in sections Memory Model and Execution Model.
What is OpenSHMEM?#
OpenSHMEM is a Partitioned Global Address Space (PGAS) library interface specification. OpenSHMEM aims to provide a standard API for SHMEM libraries to aid portability and facilitate uniform predictable results of OpenSHMEM programs by explicitly stating the behavior and semantics of the OpenSHMEM library calls. Through the different versions, OpenSHMEM will continue to address the requirements of the PGAS community. As of this specification, many existing vendors support OpenSHMEM-compliant implementations and new vendors are developing OpenSHMEM library implementations to help the users write portable OpenSHMEM code. This ensures that programs can run on multiple platforms without having to deal with subtle vendor-specific implementation differences.
The OpenSHMEM [1] effort is driven by the OpenSHMEM specification committee with continuous input from the OpenSHMEM user community. To see all of the contributors and participants for the OpenSHMEM API, please see: http://www.openshmem.org/site/Contributors. In addition to the specification, the effort includes a reference OpenSHMEM implementation, validation and verification suites, tools, a mailing list and website infrastructure to support specification activities. For more information please refer to: http://www.openshmem.org.