Hi,
I have a symmetric indefinite matrix to solve,
K = [A, B]
[B^T -S].
Minres with a block diagonal preconditioner
M = [A^{-1} 0]
[0, S^{-1}]
works quite well for this particular system.
Here A is roughly a (h.o.) mass matrix and S is the diffusion operator.
I was wondering if the bddc preconditioner can be separately applied to the sub matrices A and S, instead of directly on the big matrix K by default?
Also, how can I change the coarsetype in bddc to other solvers like the ones in the petsc library?
Best regards,
Guosheng