PGI Fortran Reference manual - The Portland Group

OpenMP Directives for Fortrangoal of the WORKSHARE construct is to effect parallel execution of non-iterative but implicitlydata parallel array assignments, FORALL, and WHERE statements and constructs intrinsic tothe Fortran language beginning with Fortran 90. The Fortran structured block contained within aWORKSHARE construct must not contain any user-defined function calls unless the function isELEMENTAL.8.8. Runtime Library RoutinesUser-callable functions are available to the programmer to query and alter the parallel executionenvironment.Unlimited OpenMP thread counts are available in all PGI configurations. The number of threads isunlicensed in the OpenMP runtime libraries - up to the hard limit of 256 threads.The following table summarizes the runtime library calls.Table 35 Runtime Library Routines SummaryRuntime Library Routines with Examplesomp_get_num_threadsReturns the number of threads in the team executing the parallel region from which it is called. When called from a serial region,this function returns 1. A nested parallel region is the same as a single parallel region. By default, the value returned by thisfunction is equal to the value of the environment variable OMP_NUM_THREADS or to the value set by the last previouscall to omp_set_num_threads().Fortraninteger function omp_get_num_threads()omp_set_num_threadsSets the number of threads to use for the next parallel region.This subroutine can only be called from a serial region of code. If it is called from within a parallel region, or from within asubroutine that is called from within a parallel region, the results are undefined. Further, this subroutine has precedence over theOMP_NUM_THREADS environment variable.Fortranomp_get_thread_numsubroutine omp_set_num_threads(scalar_integer_exp)Returns the thread number within the team. The thread number lies between 0 and omp_get_num_threads()-1. Whencalled from a serial region, this function returns 0. A nested parallel region is the same as a single parallel region.Fortraninteger function omp_get_thread_num()omp_get_ancestor_thread_numReturns, for a given nested level of the current thread, the thread number of the ancestor.Fortraninteger function omp_get_ancestor_thread_num(level)integer levelomp_get_active_levelPGI Fortran Reference Guide 180