[petsc-users] Using BDDC preconditioner for assembled matrices

[Abdullah Ali Sivas]

Dear all,

I have a series of linear systems coming from a PDE for which BDDC is an
optimal preconditioner. These linear systems are assembled and I read them
from a file, then convert into MATIS as required (as in
https://www.mcs.anl.gov/petsc/petsc-current/src/ksp/ksp/examples/tutorials/ex72.c.html
). I expect each of the systems converge to the solution in almost same
number of iterations but I don't observe it. I think it is because I do not
provide enough information to the preconditioner. I can get a list of inner
dofs and interface dofs. However, I do not know how to use them. Has anyone
have any insights about it or done something similar?

Best wishes,
Abdullah Ali Sivas
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