Poor performance with BoomerAMG?

[knutert at stud.ntnu.no]

Hi Ben,

Thank you for answering. With gmres and boomeramg I get a run time of
2s, so that is much better. However, if I increase the grid size to
513x513, I get a run time of one minute. With richardson, it fails to  
converge.
LU gives 6 seconds, CG and ICC gives 7s, and the DMMG solver 3s for  
the 513x513 problem.

When using the DMMG framework, I just used the default solvers.
I use the Galerkin process to generate the coarse matrices for
the multigrid cycle.

Best,
Knut

Siterer Ben Tay <zonexo at gmail.com>:

> Hi Knut,
>
> I'm currently using boomeramg to solve my poisson eqn too. I'm using it
> on my structured C-grid. I found it to be faster than LU, especially as
> the grid size increases. However I use it as a preconditioner with
> GMRES as the solver. Have you tried this option? Although it's faster,
> the speed increase is usually less than double. It seems to be worse if
> there is a lot of stretching in the grid.
>
> Btw, your mention using the DMMG framework and it takes less than a
> sec. What solver or preconditioner did you use? It's 4 times faster
> than GMRES...
>
> thanks!
>
> knutert at stud.ntnu.no wrote:
>> Hello,
>>
>> I am trying to use the hypre multigrid solver to solve a Poisson equation.
>> However, on a test case with grid size 257x257 it takes 40 seconds   
>> to converge
>> on one processor when I run with
>> ./run -ksp_type richardson -pc_type hypre -pc_type_hypre boomeramg
>>
>> Using the DMMG framework, the same problem takes less than a second,
>> and the default gmres solver uses only four seconds.
>>
>> Am I somehow using the solver the wrong way, or is this performance  
>>  expected?
>>
>> Regards
>> Knut Erik Teigen
>>
>>