Thanks for the input but it still doesn't work for me... Here's the
version without MPI_IN_PLACE that does work:
program test
use mpi
integer :: ierr, myrank, a(2), a_loc(2) = 0
call MPI_Init(ierr)
call MPI_Comm_rank(MPI_COMM_WORLD,myrank,ierr)
if (myrank == 0) then
a_loc(1) = 1
a_loc(2) = 2
else
a_loc(1) = 3
a_loc(2) = 4
endif
call MPI_Allreduce(a_loc,a,2,MPI_INTEGER,MPI_SUM,MPI_COMM_WORLD,ierr)
write(*,*) myrank, a(:)
call MPI_Finalize(ierr)
end program test
$ openmpif90 test.f90
$ openmpirun -np 2 a.out
0 4 6
1 4 6
Now I'd be curious to know why your OpenMPI implementation handles
MPI_IN_PLACE correctly and not mine!
--
Hugo Gagnon
On Fri, Sep 6, 2013, at 22:37, Tom Rosmond wrote:
> Hello,
>
> Your syntax defining 'a' is not correct. This code works correctly.
>
> program test
> use mpi
> integer :: ierr, myrank, a(2) = 0
> call MPI_Init(ierr)
> call MPI_Comm_rank(MPI_COMM_WORLD,myrank,ierr)
> if (myrank == 0) then
> a(1) = 1
> a(2) = 2
> else
> a(1) = 3
> a(2) = 4
> endif
> call
> MPI_Allreduce(MPI_IN_PLACE,a,2,MPI_INTEGER,MPI_SUM,MPI_COMM_WORLD,ierr)
> write(*,*) myrank, a(:)
> call MPI_Finalize(ierr)
> end program test
>
> mpif90 test.f90
> mpirun -np 2 a.out
> 0 4 6
> 1 4 6
>
> T. Rosmond
>
>
>
>
>
> On Fri, 2013-09-06 at 21:27 -0400, Hugo Gagnon wrote:
> > Hello,
> >
> > I'm trying to run this bit of code:
> >
> > program test
> > use mpi
> > integer :: ierr, myrank, a(2) = 0
> > call MPI_Init(ierr)
> > call MPI_Comm_rank(MPI_COMM_WORLD,myrank,ierr)
> > if (myrank == 0) a(1) = 1; a(2) = 2
> > if (myrank == 1) a(1) = 3; a(2) = 4
> > call
> > MPI_Allreduce(MPI_IN_PLACE,a,2,MPI_INTEGER,MPI_SUM,MPI_COMM_WORLD,ierr)
> > write(*,*) myrank, a(:)
> > call MPI_Finalize(ierr)
> > end program test
> >
> > but the output is not what I'd expect:
> >
> > $ openmpif90 test.f90
> > $ openmpirun -np 2 a.out
> > 0 0 0
> > 1 0 0
> >
> > I tried a version without MPI_IN_PLACE and the call to MPI_Allreduce
> > works fine in that case. Am I doing something wrong with MPI_IN_PLACE?
> > I'm using OpenMPI 1.6.5 compiled with gcc 4.8.1 on Mac OS 10.8.
> >
> > Thanks,
>
>
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