MAT_KEEP_ZEROED_ROWS && MatZeroRows() on empty rows.

[Lisandro Dalcin]

A co-worker (CC'ed) pointed me this:

$ cat zerorows.py
from petsc4py import PETSc
A = PETSc.Mat().createAIJ(5)
A[0,0] = 1
A[4,4] = 1
A.assemble()
A.setOption(PETSc.Mat.Option.KEEP_ZEROED_ROWS, True)
A.zeroRows([1,2,3])
A.view()


$ python zerorows.py
Traceback (most recent call last):
  File "zerorows.py", line 7, in <module>
    A.zeroRows([2])
  File "Mat.pyx", line 621, in petsc4py.PETSc.Mat.zeroRows
(src/petsc4py.PETSc.c:63679)
petsc4py.PETSc.Error: error code 73
[0] MatZeroRows() line 4822 in src/mat/interface/matrix.c
[0] MatZeroRows_SeqAIJ() line 1367 in src/mat/impls/aij/seq/aij.c
[0] Object is in wrong state
[0] Matrix is missing diagonal entry in row 3

If the setOption() is commented out, all work as expected.

Is this a bug? What do you think?
We could argue this is an abuse of ZeroRows() (I mean, use ZeroRows()
to put something on diagonal when we know in advance that the whole
row is empty).
However, as the call succeed  without the setOption(KEEP_ZEROED_...),
I'm inclined to think this is actually a bug.


-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
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