On Thu, Nov 21, 2013 at 3:43 PM, Dave May <[email protected]> wrote:
> Is using the "big communicator" really the right way to go? What happens > when I call VecNorm() when the local size on most ranks =0.. the global > reduction still has to be performed and all ranks in the original > communicator associated with the fine get participate. > > I thought the primary advantage/reason to use less ranks with small > distributed systems was to avoid seeing the network latency when there is > little computational work. I don't see how using the big communicator > avoids this. > Its not just this. You do not want to get to the point where you have 1 or < 1 point per process, so you rebalance to put a reasonable number of unknowns per process and leave others empty. You could create a subcomm with only the nonzero procs to use in the solve. Not sure if this is worth it. Matt > Am I missing something? > > Cheers, > Dave > > On Thursday, 21 November 2013, Jed Brown wrote: > >> John Mousel <[email protected]> writes: >> >> > Thanks Jed. How does this represent itself in the KSPView output? >> >> I'm afraid it's not there, though you can extract the ownership ranges >> From code. >> > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
