On Thu, Mar 8, 2012 at 13:59, Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>wrote:
> And last one is more appreciated; > -mg_levels_1_ksp_type cg can this be written in routine ? yes, with > KSPSetType() but which ksp-context ? ksp_pre ? > That is the command line option, see PCMGGetSmoother() or PCMGGetSmootherUp() to get the KSP for a level from code. > > My Preconditioner: > I need a preconditioner which read as: Prec = \lambda_max*C + (I - AC) , > [C = CGC] where (I - AC) deflates spectrum to zero, > and this part \lambda_max *C then shifts spectrum to \lambda_max (which > is always 1 in my case) . > You can always multiply preconditioners by a arbitrary constant, so multiply through by S = 1/\lambda_max to get the standard form Prec = C + S(I - AC) > Dont I get my Prec by multiplicative combination of CGC with post smoother > S = Identity using mg_type_multiplicative ? If we put in S = I, we get my Prec = C + I - AC which is not equal to your stated Prec = I - AC unless C = 0 which would make Prec = I. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120308/d513115e/attachment.htm>
