Hi
there, My name is Pedro Ricardo and I'm currently a researcher at a Fluid Dynamics Laboratory in Brazil.
We
have a CFD software with 12 continuous years of development mostly in Fortran, and we've been using Mpich and Openmpi since the very beginning.
Recently we started to refactor the code and write it using Fortran2008 standard and this includes the usage of the the newest MPI module for Fortran "mpi_f08".
So far no errors were present in Openmpi implementations and everything worked like a charm, but when we started compiling with Mpich lots of errors happened during execution.
I was able so isolate and reproduce the error in a simpler code. Whenever "use mpi_f08"
is present, the arrays passed to a MPI subroutine return with C-like indexes. If I allocate an standard array in Fortran (that starts with index 1),
after the call of some MPI routine this array come back starting with index 0.
And you can imagine that all access to this array will be wrong after that.
It is a funny behavior because if you put "use mpi"
instead of "use mpi_f08", the indexes do not change.
The test is simple, allocate and array, print it's bound indexes, calls a MPI_Reduce routine and print the array bounds
again. I've also tested other routines like MPI_ISend and the error
also happens.
program check_bounds
!Check Works
! use mpi
!Check Fails
use mpi_f08
implicit none
integer:: mpi_ierr, proc_id, n_proc
real, allocatable, dimension(:):: t1, t1_0
call MPI_Init(mpi_ierr)
call MPI_Comm_rank(MPI_COMM_WORLD, proc_id, mpi_ierr)
call MPI_Comm_size(MPI_COMM_WORLD, n_proc, mpi_ierr)
allocate(t1(5), t1_0(5))
t1 = 1.0; t1_0 = 1.0
if (proc_id==0) then
write(*,*)'Array Configuration Before:'
write(*,'(a6,2(1x,i2))')'Low:',lbound(t1),lbound(t1_0)
write(*,'(a6,2(1x,i2))')'Upper:',ubound(t1),ubound(t1_0)
end if
CALL MPI_REDUCE(t1, t1_0, 5, MPI_REAL, MPI_SUM, 0, MPI_COMM_WORLD, mpi_ierr)
if (proc_id==0) then
write(*,*)'Array Configuration After:'
write(*,'(a6,2(1x,i2))')'Low:',lbound(t1),lbound(t1_0)
write(*,'(a6,2(1x,i2))')'Upper:',ubound(t1),ubound(t1_0)
end if
deallocate(t1, t1_0)
call MPI_Finalize(mpi_ierr)
end program check_bounds
Thanks
for the attention,