<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>Hi Dave,</div>
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<div>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.</div>
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Marius </div>
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<blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex;border-left: 1.0px rgb(204,204,204) solid;padding-left: 1.0ex;">Hi,<br/>
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What is PetscObjectGetComm expected to return?</blockquote>
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<div>As Patrick said, it returns the communicator associated with the petsc object.</div>
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<blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex;border-left: 1.0px rgb(204,204,204) solid;padding-left: 1.0ex;">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.</blockquote>
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<div>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?</div>
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<blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex;border-left: 1.0px rgb(204,204,204) solid;padding-left: 1.0ex;">That said, is there a way to get the MPI communicator a matrix lives on?</blockquote>
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<div>You are using the correct function. There is a macro as well but it’s best to use the function.</div>
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<div>Thanks,</div>
<div>Dave</div>
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Best,<br/>
Marius</blockquote>
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