Terry Wilmarth d8e4cb9121 [OpenMP] libomp: Add new experimental barrier: two-level distributed barrier ... Two-level distributed barrier is a new experimental barrier designed for Intel hardware that has better performance in some cases than the default hyper barrier. This barrier is designed to handle fine granularity parallelism where barriers are used frequently with little compute and memory access between barriers. There is no need to use it for codes with few barriers and large granularity compute, or memory intensive applications, as little difference will be seen between this barrier and the default hyper barrier. This barrier is designed to work optimally with a fixed number of threads, and has a significant setup time, so should NOT be used in situations where the number of threads in a team is varied frequently. The two-level distributed barrier is off by default -- hyper barrier is used by default. To use this barrier, you must set all barrier patterns to use this type, because it will not work with other barrier patterns. Thus, to turn it on, the following settings are required: KMP_FORKJOIN_BARRIER_PATTERN=dist,dist KMP_PLAIN_BARRIER_PATTERN=dist,dist KMP_REDUCTION_BARRIER_PATTERN=dist,dist Branching factors (set with KMP_FORKJOIN_BARRIER, KMP_PLAIN_BARRIER, and KMP_REDUCTION_BARRIER) are ignored by the two-level distributed barrier. Patch fixed for ITTNotify disabled builds and non-x86 builds Co-authored-by: Jonathan Peyton <jonathan.l.peyton@intel.com> Co-authored-by: Vladislav Vinogradov <vlad.vinogradov@intel.com> Differential Revision: https://reviews.llvm.org/D103121		2021-07-29 14:09:26 -05:00
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omp_barrier.c	[OpenMP] libomp: Add new experimental barrier: two-level distributed barrier	2021-07-29 14:09:26 -05:00