Dear all, Dear Jeff,
I am very sorry, but I do not know how to do this kind of comparison.
this is my peace of code:
CALL MPI_GROUP_INCL(GROUP_WORLD, nPSObranch, MRANKS, MASTER_GROUP,ierr)
CALL MPI_COMM_CREATE_GROUP(MPI_COMM_WORLD,MASTER_GROUP,0,MASTER_COMM,iErr)
!
IF(MPI_COMM_NULL .NE. MASTER_COMM)THEN
CALL MPI_COMM_RANK(MASTER_COMM, MPImaster%rank,MPIlocal%iErr)
CALL MPI_COMM_SIZE(MASTER_COMM, MPImaster%nCPU,MPIlocal%iErr)
ELSE
MPImaster%rank = MPI_PROC_NULL
ENDIF
and then
IF(MPImaster%rank.GE.0)THEN
CALL MPI_SCATTER(PP, 10, MPI_DOUBLE, PPL, 10,MPI_DOUBLE, 0,
MASTER_COMM, iErr)
ENDIF
What I should compare?
Thanks again
Diego
On 1 August 2017 at 16:18, Jeff Squyres (jsquyres) <[email protected]>
wrote:
> On Aug 1, 2017, at 5:56 AM, Diego Avesani <[email protected]> wrote:
> >
> > If I do this:
> >
> > CALL MPI_SCATTER(PP, npart, MPI_DOUBLE, PPL, 10,MPI_DOUBLE, 0,
> MASTER_COMM, iErr)
> >
> > I get an error. This because some CPU does not belong to MATER_COMM. The
> alternative should be:
> >
> > IF(rank.LT.0)THEN
> > CALL MPI_SCATTER(PP, npart, MPI_DOUBLE, PPL, 10,MPI_DOUBLE, 0,
> MASTER_COMM, iErr)
> > ENDIF
>
> MPI_PROC_NULL is a sentinel value; I don't think you can make any
> assumptions about its value (i.e., that it's negative). In practice, it
> probably always is, but if you want to check the rank, you should compare
> it to MPI_PROC_NULL.
>
> That being said, comparing MASTER_COMM to MPI_COMM_NULL is no more
> expensive than comparing an integer. So that might be a bit more expressive
> to read / easier to maintain over time, and it won't cost you any
> performance.
>
> --
> Jeff Squyres
> [email protected]
>
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