Praveen C <[email protected]> writes: > So I have to create a global vector AND a local vector using > DMCreateLocalVector. > > Then I do DMGlobalToLocalBegin/End. Does this not lead to too much copying > ?
It's typically more efficient -- the solver gets to work with contiguous vectors and doesn't have unused "ghost" storage in every vector of a Krylov space, for example. > I see there is VecCreateGhost but no such thing for DMDA ? That would necessitate non-contiguous indexing which would kill performance. Also note that the ghost points in a VecGhost would exist but be unused in every vector of a Krylov space, every stage of a Runge-Kutta method, etc. Much better to have one or two local vectors that you use while evaluating residuals. > PS: Would be nice if the reply-to was set to mailing list. I frequently > forget to do Reply All. Then make reply-all your default instead of asking to break (individual) reply for everyone else. http://www.unicom.com/pw/reply-to-harmful.html http://woozle.org/~neale/papers/reply-to-still-harmful.html
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