gfortran and mpich2 interaction

[jdelia at intec dot unl dot edu dot ar]

Dear gfortran developers,

From the first distributions of the GFORTRAN compiler (experimental  
or not), I had noticed a little execution problem (of low impact) when  
the attached test program runs in parallel using MPICH2. I ignore if  
it is a problem of GFORTRAN or MPICH2 but it does not happen neither  
with g95 nor with ifort.

In the  simple test, in parallel, the processor 0 must read a variable  
"n" that is entered by
console. During the execution (including the case with a single  
process), it does not
print any message until a value is entered for the required variable.

In the present test I used the current 1.0.7 stable version of MPICH2
(http://www.mcs.anl.gov/research/projects/mpich2/downloads/index.php?s=downloads)

$ which mpif90
/usr/local/mpich2-exp/1.0.7/bin/mpif90

$ mpif90 --version
GNU Fortran (GCC) 4.4.0 20080302 (experimental) [trunk revision 132813]
Copyright (C) 2007 Free Software Foundation, Inc.

GNU Fortran comes with NO WARRANTY, to the extent permitted by law.
You may redistribute copies of GNU Fortran
under the terms of the GNU General Public License.
For more information about these matters, see the file named COPYING

$ mpif90 -Wall -std=f2003 -fPIC -o testinputmpi.exe testinputmpi.f90

$ mpiexec -machinefile ~/machi.dat -np 1 testinputmpi.exe
100
100
100
  matrix rank ; n : ?
  matrix rank ; n =          100
  matrix rank ; n : ?
  matrix rank ; n =          100
  matrix rank ; n : ?
  matrix rank ; n =          100

The nodes of our Beowulf cluster are 32-bit processors (i386, Intel  
Pentium 4).

Perhaps, in case that the problem is in gfortran, is there some compilation
flag for fix this little trouble ?

Thanks in advance,

Regards,
Jorge.

! -----------------------------------------------------------------
! MPICH2
!  which mpif90
!  mpif90 --version
!  mpif90 -Wall -std=f2003 -fPIC -o testinputmpi.exe testinputmpi.f90
!  mpdboot -n 5 -f ~/mpd.hosts
!  mpdtrace
!  mpdringtest
!  mpiexec -machinefile ~/machi.dat -np 2 testinputmpi.exe
!  mpdallexit
!
! -----------------------------------------------------------------
program testinputmpi
  use mpi
  implicit none
  integer :: myid, siza, ierr, master=0, n
  !
  call MPI_Init (ierr)
  call MPI_Comm_size (MPI_COMM_WORLD, siza, ierr) ! number of processes
  call MPI_Comm_rank (MPI_COMM_WORLD, myid, ierr) ! my rank
  !
  if (myid == master) then
    ! alternative 1
    write (*,*)
    write (*,*) " matrix rank ; n : ? "
    read  (*,*) n
    write (*,*) " matrix rank ; n = ", n
    ! alternative 2
    write (6,*)
    write (6,*) " matrix rank ; n : ? "
    read  (5,*) n
    write (6,*) " matrix rank ; n = ", n
    ! alternative 3
    print  *
    print  *,   " matrix rank ; n : ? "
    read  (*,*) n
    print  *,   " matrix rank ; n = ", n
  else
    write (*,*) "hellow from ", myid, " of ", siza, "processes"
  end if
  !
  call MPI_Finalize (ierr)
  !
end program
! -------------------------------------------------------------------

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