[petsc-dev] boomerAmg scalability

[Mark F. Adams]

On Dec 15, 2011, at 1:56 PM, Matthew Knepley wrote:

> On Thu, Dec 15, 2011 at 10:23 AM, Ravi Kannan <rxk at cfdrc.com> wrote:
> Dear All,
> 
>  
> 
> This is Ravi Kannan from CFD Research Corporation. Recently, we are experimenting with the BoomerAMG preconditioner for some “stiff” CFD problems. In that regard, all the other standard solver-preconditioner combinations failed for the current CFD problem. The boomer is the only one which is able to provide with “converged” solutions.
> 
>  
> 
> We noticed that the scalability of this boomer preconditioner is really poor. For instance, even with a cell size of 2 million, we cannot scale to even 16 partitions (in contrast, the other solver-preconditioner combinations like the BI-CGS/BJacobi gave good enough scalability).
> 
>  
> 
> Are we missing something? Do we need to use a more latest version of boomer?
> 
> 
> Have you tried -pc_type gamg in petsc-dev?

For gamg you also want to use MPIAIJ matrices and set the block size MatSetBlockSize(mat,3), for a 3D velocity field, for instance.  You can also try '-pc_gamg_type pa' or '-pc_gamg_type sa'.  "pa", for plain aggregation might be better for CFD problems.

Mark

> 
>   Matt
>   
> Thanks,
> 
> Ravi.
> 
> 
> 
> 
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener

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