I was commenting on one of Diego's previous solutions where all non-master processes were using the color set to MPI_COMM_NULL in MPI_COMM_SPLIT.
Overall comparing with MPI_COMM_NULL as you suggested is indeed the cleanest solution. George. On Wed, Aug 2, 2017 at 1:36 PM, Jeff Squyres (jsquyres) <jsquy...@cisco.com> wrote: > George -- > > Just to be clear, I was not suggesting that he split on a color of > MPI_COMM_NULL. His last snippet of code was: > > ----- > 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 > > ... > > IF(MPImaster%rank.GE.0)THEN > CALL MPI_SCATTER(PP, 10, MPI_DOUBLE, PPL, 10,MPI_DOUBLE, 0, > MASTER_COMM, iErr) > ENDIF > ----- > > In particular, the last "IF(MPImaster%rank.GE.0)" -- he's checking to see > if the MPImaster%rank was set to MPI_PROC_NULL. I was just suggesting that > he change that to "IF(MPI_COMM_NULL .NE. MASTER_COMM)" -- i.e., he > shouldn't make any assumptions about the value of MPI_PROC_NULL, etc. > > > > > On Aug 2, 2017, at 12:54 PM, George Bosilca <bosi...@icl.utk.edu> wrote: > > > > Diego, > > > > Setting the color to MPI_COMM_NULL is not good, as it results in some > random value (and not the MPI_UNDEFINED that do not generate a > communicator). Change the color to MPI_UNDEFINED and your application > should work just fine (in the sense that all processes not in the master > communicator will have the master_comm variable set to MPI_COMM_NULL). > > > > George. > > > > > > > > On Wed, Aug 2, 2017 at 10:15 AM, Diego Avesani <diego.aves...@gmail.com> > wrote: > > Dear Jeff, Dear all, > > > > thanks, I will try immediately. > > > > thanks again > > > > > > > > Diego > > > > > > On 2 August 2017 at 14:01, Jeff Squyres (jsquyres) <jsquy...@cisco.com> > wrote: > > Just like in your original code snippet, you can > > > > If (master_comm .ne. Mpi_comm_null) then > > ... > > > > Sent from my phone. No type good. > > > > On Aug 2, 2017, at 7:17 AM, Diego Avesani <diego.aves...@gmail.com> > wrote: > > > >> 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) <jsquy...@cisco.com> > wrote: > >> On Aug 1, 2017, at 5:56 AM, Diego Avesani <diego.aves...@gmail.com> > 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 > >> jsquy...@cisco.com > >> > >> _______________________________________________ > >> users mailing list > >> users@lists.open-mpi.org > >> https://lists.open-mpi.org/mailman/listinfo/users > >> > >> _______________________________________________ > >> users mailing list > >> users@lists.open-mpi.org > >> https://lists.open-mpi.org/mailman/listinfo/users > > > > _______________________________________________ > > users mailing list > > users@lists.open-mpi.org > > https://lists.open-mpi.org/mailman/listinfo/users > > > > > > _______________________________________________ > > users mailing list > > users@lists.open-mpi.org > > https://lists.open-mpi.org/mailman/listinfo/users > > > > _______________________________________________ > > users mailing list > > users@lists.open-mpi.org > > https://lists.open-mpi.org/mailman/listinfo/users > > > -- > Jeff Squyres > jsquy...@cisco.com > > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/users >
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