[petsc-users] Elliptic operator with Neumann conditions

[Marco Cisternino]

Hi everybody,
I would like to ask what solution is computed if I try to solve the linear system relative to the problem in subject without creating the null space.
I tried with and without the call to
MatNullSpaceCreate(m_communicator, PETSC_TRUE, 0, NULL, &nullspace);
and I get zero averaged solution with and the same solution plus a constant without.
How does PETSc  work in the second case?
Does it check the matrix singularity? And is it able to create the null space with the constant automatically?
Thanks.


Marco Cisternino, PhD
marco.cisternino at optimad.it
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