da_proc_sum_int.inc

1 subroutine da_proc_sum_int (value)
2 
3    !---------------------------------------------------------------------------
4    !  Purpose: Do MPI sum operation across processors to get the global sum of
5    !           an integer value. The sum is returned only on the root processor,
6    !           i.e., processor 0. (In this way, we do not have to do all-to-all 
7    !           communication, unlike wrf_dm_sum_int, which does)
8    !
9    ! The routine generates a MPI barrier
10    !---------------------------------------------------------------------------
11 
12    implicit none
13 
14    integer, intent(inout) :: value     ! Value on processor.
15 
16 #ifdef DM_PARALLEL
17    integer :: sum                   ! Sum across processors.
18 
19    ! Don't trace, as called within trace routines
20    ! if (trace_use_frequent) call da_trace_entry("da_proc_sum_int")
21 
22    sum=0
23    call mpi_reduce(value, sum, 1, mpi_integer, mpi_sum, root, &
24       comm, ierr)
25 
26    if (rootproc) value = sum
27 
28    ! if (trace_use_frequent) call da_trace_exit("da_proc_sum_int")
29 #endif
30 
31 end subroutine da_proc_sum_int
32 
33