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