Fortran and MPI

[dcs4]

Hi boys.

I'm trying to call a barrier in a MPI program with Fortran, but I don't know how do it.

I don't have any problem with the main program, but i have a lot of problems with the comunicator when I have tried to do it in a Fortran Routine. I don't know how I can do it. Can you give me an example?

Thanks in advande

 

[xwb]

The barrier basically stops execution until all the processes call it.

program main
include 'mpif.h'
integer ierr
integer rank, sleepsec
character(10):: now

! Initialize the MPI environment
call MPI_Init(ierr)

! Find the node
call MPI_Comm_rank(MPI_COMM_WORLD, rank, ierr)

sleepsec = 5 * rank
call date_and_time(time=now)
print *, rank, ' sleeping for ', sleepsec, ' from ', now
call SLEEP(sleepsec)
call MPI_BARRIER(MPI_COMM_WORLD, ierr)
call date_and_time(time=now)
print *, rank, ' awake ', now
call MPI_FINALIZE(ierr)
end

mpif90 -o barrier barrier.f90

mpirun -n 4 barrier

What you will see is that the different processes sleep for differing numbers of seconds but they all only awake when the longest sleeping process callse MPI_BARRIER.

 

[xwb]

The example uses gfortran and the open MPI package that comes with Linux. You didn't specify which compiler/operating system you were using with MPI.