On Jan 7, 2013, at 8:05 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> It's sort of awkward to deal with PCREDUNDANT for coarse grids, and I have > yet to see any evidence that it's better than gathering to rank 0, solving > sequentially, and scattering the result. What about implementing LU for > MPIAIJ to do the latter algorithm? Then we could trivially make it smart > enough to skip the gather when Mark uses it on the coarse grid of GAMG (where > the entire system is already on rank 0). In additon to being simpler for the > user to interact with, this would fix a lot of fighting between the PCMG and > its children. I thought PCREDUNDANT had this ability? What about adding it? Have an option that cause PCREDUNDANT to only collect a single copy of the matrix from rank 0 to r-1 and in your case r is 1. I hate the idea of having another separate place with similar stuff to PCREDUNDANT. You could then implement LU for MPIAIJ using this variant of PCREDUNDANT, that is a call to PCREDUNDANT stuff with the right options. Barry
