[petsc-users] PetscObjectGetComm

[Jose E. Roman]

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 <mbuerkle at web.de> escribió:
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> Hi Dave,
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> 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.
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> Marius 
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> Hi,
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> What is PetscObjectGetComm expected to return?
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> As Patrick said, it returns the communicator associated with the petsc object.
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> 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.
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> 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?
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> That said, is there a way to get the MPI communicator a matrix lives on?
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> You are using the correct function. There is a macro as well but it’s best to use the function.
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> Thanks,
> Dave
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> Best,
> Marius
> <test_comm.tar.gz>