[petsc-users] DMMG preconditioner used in KSP

[Shao-Ching Huang]

Thanks Barry. I will look into DMMGSetKSP and your suggestions.

Shao-Ching

On Tue, Sep 28, 2010 at 7:13 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>  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
>
>