petsc-3.13.6 2020-09-29
PetscOmpCtrlBarrier
Do barrier on MPI ranks in omp_comm contained by the PETSc OMP controller (to let slave ranks free their CPU)
Synopsis
#include "petscsys.h"
PetscErrorCode PetscOmpCtrlBarrier(PetscOmpCtrl ctrl)
Input Parameter
ctrl -a PETSc OMP controller
Notes
this is a pthread barrier on MPI processes. Using MPI_Barrier instead is conceptually correct. But MPI standard does not
require processes blocked by MPI_Barrier free their CPUs to let other processes progress. In practice, to minilize latency,
MPI processes stuck in MPI_Barrier keep polling and do not free CPUs. In contrast, pthread_barrier has this requirement.
A code using PetscOmpCtrlBarrier() would be like this,
if (is_omp_master) {
PetscOmpCtrlOmpRegionOnMasterBegin(ctrl);
Call the library using OpenMP
PetscOmpCtrlOmpRegionOnMasterEnd(ctrl);
}
PetscOmpCtrlBarrier(ctrl);
See Also
PetscOmpCtrlOmpRegionOnMasterBegin(), PetscOmpCtrlOmpRegionOnMasterEnd()
Level
developer
Location
src/sys/utils/mpishm.c
Index of all Sys routines
Table of Contents for all manual pages
Index of all manual pages