GMRES performance

[jarunan at ascomp.ch]

Hello,

I followed the suggestion in PETSc previous threads by adding options

-pc_type asm -sub_pc_type lu

Now the solver is really fast!!!!!

Thanks you
Jarunan




Quoting Barry Smith <bsmith at mcs.anl.gov>:

>
> On Oct 20, 2009, at 9:52 AM, jarunan at ascomp.ch wrote:
>
>> Hello,
>>
>> I would like to know some information about GMRES performance in   
>> PETSc if you have any experience.
>>
>> I am running a parallel test case(9300 cells) comparing cpu time   
>> using by solvers in Petsc. While BICGSTAB was doing 0.9 sec, GMRES   
>> 15 sec with the same preconditioner(Additive Schwarz). I did not   
>> expect that GMRES would be that much slower. Everything is default.
>
>    You need much more information than runtimes of the two cases to
> understand why one is faster than the other.
>>
>> Please share your experiences, how the performance of solvers are   
>> in your test cases. Which option I should set to improve GMRES   
>> performance? Is there the best combination of Preconditioner and   
>> solver?
>
>    Run both (with debugging turned off, hence optimized) using the
> option -log_summary and look at where each is code is spending its
> time. You can also see how many iterations (MatMult) each solver is
> requiring. Feel free to send the -log_summary output to
> petsc-maint at mcs.anl.gov if you do not understand it.
>
>    Barry
>
>>
>> Thank you very much
>> Jarunan
>>
>> -- 
>> Jarunan Panyasantisuk
>> Development Engineer
>> ASCOMP GmbH, Technoparkstr. 1
>> CH-8005 Zurich, Switzerland
>> Phone : +41 44 445 4072
>> Fax   : +41 44 445 4075
>> E-mail: jarunan at ascomp.ch
>> www.ascomp.ch



-- 
Jarunan Panyasantisuk
Development Engineer
ASCOMP GmbH, Technoparkstr. 1
CH-8005 Zurich, Switzerland
Phone : +41 44 445 4072
Fax   : +41 44 445 4075
E-mail: jarunan at ascomp.ch
www.ascomp.ch