[petsc-users] Help with petsc4py and PC Python type

[Justin Chang]

Hi all,

I am attempting to write my own scour preconditioner for a FEniCS/petsc4py.
I managed to attach a DMShell to the KSP so that I can employ command-line
options for field splitting. Suppose I want to solve the Navier-Stokes
equation and have the following command-line options:

-ksp_type fgmres
-pc_type fieldsplit
-pc_fieldsplit_type schur
-pc_fieldsplit_schur_fact_type full
-fieldsplit_0_ksp_type gmres
-fieldsplit_0_pc_type hypre
-fieldsplit_1_ksp_type preonly
-fieldsplit_1_pc_type python
-fieldsplit_1_pc_python_type pfibs.MyPCD

Where MyPCD is part of my pfibs module and looks something like this:

class MyPCD(object):
    def setUp(self, pc):
          # Do something #
             ....
    def apply(self, pc, x, y):
          # Do something #
             ....

The problem is that in my actual python code (mycode.py) I have a dict()
object that I would like to pass into the setUp() call inside MyPCD to read
in, but it is not clear how I can do this if I set the pc python type via
command line options. If I hard-coded this, I would just call
pc.setPythonContext(...) but I was wondering if there's a way to do this,
e.g., attaching an appctx/dict to the pc itself. Does anyone have ideas or
suggestions on how to go about doing this?

Thanks,
Justin
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