Hey All,

I was wondering if anyone had used MatNest with petsc4py. I am having
issues trying to create a MatNest where some of the submatrices are
empty. In PETSc, I can just pass NULL in the array that I give to
MatCreateNest and it works fine. However, the following code

nest_list = [[None,None],[None,None]]
nest_list[0][0] = some matrix
nest_list[0][1] = some matrix
nest_list[1][0] = some matrix
A = PETSc.Mat().createNest(nest_list,comm=PETSc.COMM_WORLD)

fails with:
  File "Mat.pyx", line 445, in petsc4py.PETSc.Mat.createNest
(src/petsc4py.PETSc.c:103202)
TypeError: Cannot convert NoneType to petsc4py.PETSc.Mat

Is there an equivalent to NULL in petsc4py (there doesn't appear to be one)?

If all of the entries in nest_list are filled, everything works fine.

Any help would be appreciated!

Thanks,
Chris

-- 
Chris Eldred
Postdoctoral Fellow, LAGA, University of Paris 13
PhD, Atmospheric Science, Colorado State University, 2015
DOE Computational Science Graduate Fellow (Alumni)
B.S. Applied Computational Physics, Carnegie Mellon University, 2009
[email protected]

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