• 2019 Update 4
  • 03/20/2019
  • Public Content

Work-Group Level Parallelism

Since work-groups are independent, they can execute concurrently on different hardware threads. So the number of work-groups should be not less than the number of logical cores. A larger number of work-groups results in more flexibility in scheduling, at the cost of task-switching overhead.
Notice that multiple cores of a CPU as well as multiple CPUs (in a multi-socket machine) constitute a single OpenCL device. Separate cores are compute units. The Device Fission extension enables you to control compute unit utilization within a compute device. You can find more information on the Device Fission in the Intel® Code Builder for OpenCL™ API - User Manual.
For the best performance and parallelism between work-groups, ensure that execution of a work-group takes at least 100,000 clocks. A smaller value increases the proportion of switching overhead compared to actual work.

Product and Performance Information


Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804