On Thu, Dec 29, 2011 at 11:01, Dave Nystrom <dnystrom1 at comcast.net> wrote:
> 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? > Yes > 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. > Likely pointless because this solve is probably not a big part of run-time. The bigger concern is the convergence rate that you lose by using this approximation. Matt and I mentioned this the last time you brought it up, but I recommend getting familiar with the literature. Then, get the math straight before looking for ways to transform into problems that you can run fast on a GPU or whatever. If you just optimize kernels, you're likely to optimize something that takes a small part of run-time and isn't really helping you anyway. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20111229/4cac74de/attachment.html>
