[petsc-users] DMMG preconditioner used in KSP

[Barry Smith]

  If you are using DMMGSetKSP() then just have the third argument (func) compute A+B as the first matrix and A as the second matrix. Then the smoothing and coarse grid solve will 
only use the A entries. That is A+B will be preconditioned with geometric multigrid applied to A.

   But, I suspect that you will do just as well using A+B.

   Barry

On Sep 28, 2010, at 8:19 PM, Shao-Ching Huang wrote:

> Hi
> 
> I can trying to solve a linear system
> 
> (A+B)x=b
> 
> where A is the standard finite difference Laplacian matrix and B has
> only a few elements (i.e. B's number of non-zero entries is much much
> smaller than A's).
> Is it possible to precondition by applying DMMG on A (like in ex34.c)
> in a KSP solver? Is there an example that I can follow to set this up?
> 
> Thanks,
> 
> Shao-Ching