MueLu: separate setup and solve of regionMG coarse level solver
Created by: mayrmt
Enhancement
@trilinos/muelu
On the coarse level, we need to perform a direct solve on the composite system. Right now, this is done by creating a Amesos2 KLU solver in every visit to the coarsest level.
Steps to do:
- Move the setup phase of the Amesos2 KLU solver to the setup of the hierarchy and store the factorizations
- Only leave the apply phase of the direct solver in the V-Cycle
Overall, this aims at reducing unnecessary (and duplicate) cost.