[petsc-users] Boomeramg as a solver

[jibum kim]

Now it is clear.

Thank you for your help.

- Jibum
----- Original Message ----- 
From: "jibum kim" <jzk164 at psu.edu>
To: "PETSc users list" <petsc-users at mcs.anl.gov>
Sent: Monday, November 01, 2010 3:46 PM
Subject: Re: [petsc-users] Boomeramg as a solver


> Are you saying that boomeramg with richardson iterations is same as the 
> multigrid without a preconditioner? and if it the case, how can I set an 
> extra preconditioner like ILU ?
>
> Thanks,
>
> - Jibum
>
> ----- Original Message ----- 
> From: "Barry Smith" <bsmith at mcs.anl.gov>
> To: "PETSc users list" <petsc-users at mcs.anl.gov>
> Sent: Monday, November 01, 2010 2:25 PM
> Subject: Re: [petsc-users] Boomeramg as a solver
>
>
>
> On Nov 1, 2010, at 12:35 PM, jibum kim wrote:
>
>> Hello,
>>
>> I've used  Boomeramg as a preconditioner.
>>
>> Now, I am wondering whether I can use Boomeramg as a solver ? and is it 
>> possible that I use Boomeramg as both a preconditioner and a solver?
>>
>> I saw one slide saying that I can use KSPSetType(ksp, KSPRICHARDSON);
>>
>> But when I try it and use -ksp_view, it shows that my solver is 
>> Richardson not  Boomeramg.
>>
>> Could u clarify this issue ?
>
>  Richardson is our name for the iterative process   u^{n+1} = u^n + B(b - 
> A u^n) for n=1,...max_it where B is the application of the preconditioner 
> (in other words running a linear iterative method without any Krylov 
> acceleration). In BoomerAMG's case B is one application of the V or W 
> cycle (depending on your choice of BoomerAMG options).  So even though it 
> says the "solver" is Richardson it is using BoomerAMG for the entire 
> solution process, that is  algebraic multigrid with multiple V (or W 
> cycles).
>
>   Barry
>
>
>
>
>>
>> Thank you.
>>
>> - Jibum
>
>