da_proc_sum_real.inc

1 subroutine da_proc_sum_real (value)
2 
3    !---------------------------------------------------------------------------
4    ! Purpose: Do MPI reduction operation across processors to sum a real 
5    ! vector.  
6    ! On return, each of the N components of the vector "value" represents
7    ! the sum of parts from each processor. The result is stored only on 
8    ! the root processor, i.e., processor 0. (In this way, we do not have 
9    ! to do all-to-all communication, unlike wrf_dm_sum_real, which does)
10    !
11    ! The routine generates a MPI barrier
12    !---------------------------------------------------------------------------
13 
14    implicit none
15 
16    real, intent(inout) :: value(:) ! Array to be summed componentwise.
17 
18 #ifdef DM_PARALLEL
19    real              :: apsum(size(value))             ! Sum across processors.
20 
21    ! Don't trace, as called within trace routines
22    !if (trace_use_frequent) call da_trace_entry("da_proc_sum_real")
23 
24    apsum(:)=0
25    call mpi_reduce(value, apsum, SIZE(value), true_mpi_real, mpi_sum, root, &
26       comm, ierr)
27 
28    if (rootproc) value = apsum
29 
30    !if (trace_use_frequent) call da_trace_exit("da_proc_sum_real")
31 #endif
32 
33 end subroutine da_proc_sum_real
34 
35