On Fri, Mar 9, 2012 at 05:16, Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>wrote:
> Dear, > > To my earlier querry: > > What if I want to approximate my all coarse matrices with any Krylov > iteration ? > > reply: > The methods on each level are independent, you can set them with > -mg_coarse_ksp_type gmres -mg_levels_1_ksp_type cg -mg_levels_1_ksp_max_it > 100 -mg_levels_2_ksp_type minres ... > > This command line option changes the ksp_type on both ksp_pre and ksp_post > (pre and post smoothing) . > Where as I need to fix the ksp_post_type as RICHARDSON to get my Prec = C > + I - AC ; > Do you want this on every level or still just the finest? > > If adapt pre_smoother as follows : > > ierr = MGGetSmootherDown(pcmg,lev,&ksp_pre); CHKERRQ(ierr); > ierr = KSPSetType(ksp_pre, KSPGMRES);CHKERRQ(ierr); > > Does ONLY setting pre_smoother as GMRES means that GMRES iterates on > coarse matrix at level = lev ? > Yes, this will only affect the pre-smoother (so it will then go to the next coarser grid, come back, and do a post-smoother). You may have to increase the number of iterations. I strongly recommend configuring the solver using the command line and checking that it is the method you intended by reading the output of -ksp_view. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120309/58a61efd/attachment-0001.htm>
