[petsc-users] Communication during MatAssemblyEnd

[Ale Foggia]

Hello all!

During the conference I showed you a problem happening during
MatAssemblyEnd in a particular code that I have. Now, I tried the same with
a simple code (a symmetric problem corresponding to the Laplacian operator
in 1D, from the SLEPc Hands-On exercises). As I understand (and please,
correct me if I'm wrong), in this case the elements of the matrix are
computed locally by each process so there should not be any communication
during the assembly. However, in the log I get that there are messages
being passed. Also, the number of messages changes with the number of
processes used and the size of the matrix. Could you please help me
understand this?

I attach the code I used and the log I get for a small problem.

Cheers,
Ale
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