I see, but I am still puzzeled, why are the communicators different on different notes eventhough it is the same object.
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 <[email protected]> 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>
https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscCommDuplicate.html
Jose
> El 22 abr 2020, a las 8:40, Marius Buerkle <[email protected]> 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>
