Closed ztdepztdep closed 1 year ago
The graph of the matrix is not enough information to decide what kind of preconditioner to use. What kind of problem is this? It looks like the discretization of a PDE, so that's good. Symmetric positive definite?
The graph of the matrix is not enough information to decide what kind of preconditioner to use. What kind of problem is this? It looks like the discretization of a PDE, so that's good. Symmetric positive definite?
It is generated from spectral element method, it is not a sysmmetric.
Alright. How about its nullspace? And what kind of physics?
Alright. How about its nullspace? And what kind of physics?
it is for incompressible flow solution. and it is a Helmholtz problem.
double-checking: By Helmholtz problem you mean: $$-\Delta u - k^2 u = f$$?
yes, it is Helmholtz problem .
Ok. These guys are difficult to precondition, as they are indefinite. I would suggest you check the literature for approaches. Both multigrid and domain decomposition can be used (and we have both in Trilinos). I believe we had some multigrid example at some point, but I'll need to find it.
yes, it is difficult. I use Amesos to precondition, but the speed is a problem.
Have a look at packages/muelu/test/helmholtz
. That's mutltigrid with a shifted Laplacian approach.
My matrix A has the following structure. I want to find an efficient preconditioner for it. I am using ifpack ilu , but i found it is too slow. could you please give me some advices.