On Wed, Apr 22, 2020 at 3:07 AM Marius Buerkle <mbuer...@web.de> wrote:
> I see, but I am still puzzeled, why are the communicators different on > different notes eventhough it is the same object. > This is the output of MPI_Comm_dup() on line 126 of tagm.c. Therefore, dup comms are not guaranteed to have the same id across multiple processes. Thanks, Matt > > > PETSc creates a duplicate of the communicator during object creation. > > https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscCommDuplicate.html > > Jose > > > > El 22 abr 2020, a las 8:40, Marius Buerkle <mbuer...@web.de> escribió: > > > > Hi Dave, > > > > I want to use it in Fortran if possible. But I tried both C and Fortran > just to see if it works in general. I am using MPICH 3.3.2. I attached the > MWE for C and Fortran with the output I get. > > > > Marius > > > > > > > > > > > > Hi, > > > > What is PetscObjectGetComm expected to return? > > > > As Patrick said, it returns the communicator associated with the petsc > object. > > > > I thought it would give the MPI communicator the object lives on. So if > I create A matrix on PETSC_COMM_WORLD a call of PetscObjectGetComm for A it > would return PETSC_COMM_WORLD? But it seems to return something else, and > while most of the nodes return a similar communicator some are giving a > different one. > > > > How are you actually comparing the communicators (send code snippet)? > Which MPI implementation are you using? And when are comparing comms is the > comparison code written in C it FORTRAN? > > > > > > That said, is there a way to get the MPI communicator a matrix lives on? > > > > You are using the correct function. There is a macro as well but it’s > best to use the function. > > > > Thanks, > > Dave > > > > > > > > > > Best, > > Marius > > <test_comm.tar.gz> > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>