On Fri, Mar 1, 2013 at 10:40 PM, Jie Chen <jiechen at mcs.anl.gov> wrote:
> I think the number of deflation vectors should not be large. So the K_c > here is a small matrix, and whether Y is dense or sparse does not make a > big difference. In this regard, deflation is not exactly the same as one > V-cycle. For multigrid, you coarsen a grid of size 1,000,000 to 500,000. > But for deflation, you reduce 1,000,000 to 10 or 50. Make sense? An alternative description for the method in the paper is "two-level unsmoothed aggregation applied to the ASM-preconditioned operator". When there are many processes/subdomains, the dimension of the coarse space can be huge. Extreme eigenvectors would be more useful, but you would still need a very large number to scale to many subdomains. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20130302/64d0cdd5/attachment.html>
