On Jun 9, 2012, at 6:51 PM, Jed Brown wrote:
> On Sat, Jun 9, 2012 at 6:43 PM, Mark F. Adams <mark.adams at columbia.edu>
> wrote:
> 1) I need a G-S kernel that takes an IS of indices to process and a flag to
> process them in forward or reverse order. How should I proceed to do this.
> Should I just clone sor?
>
> You are going to have several of these index sets? You could have a
> PCSORSetIS(). Probably need to add a MatOp for MatSORIS(). Barry might have
> other ideas.
PCSORSetIS() would then go down to MatSORSetIS() and then the call to
MatSOR() would using the IS ordering if provided, otherwise use the default
natural ordering?
I don't see a need to add a MatSORIS().
Barry
>
> 2) I don't want to use Richardson iterations for G-S. Should I make a G-S
> KPS method? I don't want to take a residual in the iterator (KSP) and if
> symmetric G-S is requested then it should drive this I think.
>
> Look at PCApplyRichardson_SOR().
>
> SOR does two sweeps in each application; I'm not wild about that because a
> good way to run G-S in a V(1,1) cycle is to do a forward sweep in pre
> smoothing and a backward sweep in post smoothing.
>
> Well, MatSOR() has this flag MatSORType that can specify forward and reverse.
> You have one PC for the down-smoother and another for the up-smoother, then
> configure one to be a forward sweep and the other to be reverse.
