Barry Smith schrieb: > > When properly running nn-cg (are you sure everything is symmetric?) > should require 10-30 iterations (certainly for model problems)
ok, this was the number I expected. > >> nn-cg on 2 nodes 229 iterations, condition 6285 >> nn-cg on 4 nodes 331 iterations, condition 13312 > > Are you sure that your operator has the null space of only constants? no, I didn't touch anything regarding the null space since I thought it would be done inside the NN-preconditioner. Does this mean I have to set up a null space of the size of the Schur complement system, i.e. the number of interface DOF's? cheers, ando > > Barry > > > On Jun 3, 2009, at 5:29 AM, Andreas Grassl wrote: > >> Barry Smith schrieb: >>> Hmm, it sounds like the difference between local "ghosted" vectors >>> and the global parallel vectors. But I do not understand why any of the >>> local vector entries would be zero. >>> Doesn't the vector X that is passed into KSP (or SNES) have the global >>> entries and uniquely define the solution? Why is viewing that not right? >>> >> >> I still don't understand fully the underlying processes of the whole PCNN >> solution procedure, but trying around I substituted >> >> MatCreateIS(commw, ind_length, ind_length, PETSC_DECIDE, PETSC_DECIDE, >> gridmapping, &A); >> >> by >> >> MatCreateIS(commw, PETSC_DECIDE, PETSC_DECIDE, actdof, actdof, >> gridmapping, &A); >> >> and received the needed results. >> >> Furthermore it seems, that the load balance is now better, although I >> still >> don't reach the expected values, e.g. >> ilu-cg 320 iterations, condition 4601 >> cg only 1662 iterations, condition 84919 >> >> nn-cg on 2 nodes 229 iterations, condition 6285 >> nn-cg on 4 nodes 331 iterations, condition 13312 >> >> or is it not to expect, that nn-cg is faster than ilu-cg? >> >> cheers, >> >> ando >> >> -- >> /"\ Grassl Andreas >> \ / ASCII Ribbon Campaign Uni Innsbruck Institut f. Mathematik >> X against HTML email Technikerstr. 13 Zi 709 >> / \ +43 (0)512 507 6091 > -- /"\ \ / ASCII Ribbon X against HTML email / \ -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 315 bytes Desc: OpenPGP digital signature URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090604/a2b62ef8/attachment.pgp>
