NAME

       shmem_barrier - Performs a barrier operation on a subset of processing elements (PEs).

SYNOPSIS

       C or C++:
       #include <mpp/shmem.h>

       void shmem_barrier(int PE_start, int logPE_stride, int PE_size,
         long *pSync);

       Fortran:
       INCLUDE "mpp/shmem.fh"

       INTEGER PE_start, logPE_stride, PE_size
       INTEGER pSync(SHMEM_BARRIER_SYNC_SIZE)

       CALL SHMEM_BARRIER(PE_start, logPE_stride, PE_size, pSync)

DESCRIPTION

       The  shmem_barrier  routine does not return until the subset of PEs specified by PE_start,
       logPE_stride and PE_size, has entered this routine at the  same  point  of  the  execution
       path.

       As with all SHMEM collective routines, each of these routines assumes that only PEs in the
       active set call the routine. If a PE not in  the  active  set  calls  a  SHMEM  collective
       routine, undefined behavior results.

       The arguments are as follows:

       PE_start
              The  lowest  virtual  PE  number of the active set of PEs. PE_start must be of type
              integer. If you are using Fortran, it must be a default integer value.

       logPE_stride
              The log (base 2) of the stride between consecutive virtual PE numbers in the active
              set.  logPE_stride  must be of type integer. If you are using Fortran, it must be a
              default integer value.

       PE_size
              The number of PEs in the active set. PE_size must be of type integer.  If  you  are
              using Fortran, it must be a default integer value.

       pSync  A   symmetric   work  array.  In  C/C++,  pSync  must  be  of  type  int  and  size
              _SHMEM_BARRIER_SYNC_SIZE. In Fortran, pSync  must  be  of  type  integer  and  size
              SHMEM_BARRIER_SYNC_SIZE.  If  you  are  using Fortran, it must be a default integer
              type.  Every element of this array must be initialized to 0 before any of  the  PEs
              in the active set enter shmem_barrier the first time.

       The  values  of  arguments PE_start, logPE_stride, and PE_size must be equal on all PEs in
       the active set. The same work array must be passed in pSync to all PEs in the active set.

       shmem_barrier ensures that all previously issued local stores and previously issued remote
       memory updates done by any of the PEs in the active set (by using SHMEM calls, for example
       shmem_put(3)) are complete before returning.

       The same pSync array may be reused on consecutive  calls  to  shmem_barrier  if  the  same
       active PE set is used.

NOTES

       The term symmetric is defined in intro_shmem(3).

       If   the  pSync  array  is  initialized  at  run  time,  be  sure  to  use  some  type  of
       synchronization, for example, a call to shmem_barrier_all(3), before calling shmem_barrier
       for the first time.

       If  the  active  set does not change, shmem_barrier can be called repeatedly with the same
       pSync array. No additional synchronization beyond that implied by shmem_barrier itself  is
       necessary in this case.

EXAMPLES

       C/C++ example:
       shmem_barrier(PE_start, logPE_stride, size, pSync);

       Fortran example:
       INTEGER PSYNC(SHMEM_BARRIER_SYNC_SIZE)
       INTEGER PE_START, LOGPE_STRIDE, PE_SIZE, PSYNC
       DATA PSYNC /SHMEM_BARRIER_SYNC_SIZE*0/

       CALL SHMEM_BARRIER(PE_START, LOGPE_STRIDE, PE_SIZE, PSYNC)

SEE ALSO

       intro_shmem(3), shmem_barrier_all(3)