I have recently added the capability to have a separate preconditioning matrix in the petsc interface for the code I am working with. I have two types of preconditioning matrices that I have questions about. One is tridiagonal and the other is 7 diagonals. In both cases, the the diagonals are all lexically adjacent. Or phrased differently, the tridiagonal matrix has a bandwidth of 3 and the 7 diagonal matrix has a bandwidth of 7 and so they are compact or dense band systems.
I was wondering what petsc ilu will do for preconditioning matrices like these. Will it produce an exact lu factorization or a nearly exact factorization? I'm interested in the answer to this question because I am thinking I might be able to run this preconditioner on the gpu using the txpetscgpu package. Thanks, Dave
