Hi Lawrence,

I don’t use any preconditioning in either of the two sets of code.

Anna.


On 7 Oct 2016, at 14:33, Lawrence Mitchell <lawrence.mitchell@imperial.ac.uk> wrote:

> Hi Anna,
>
>> On 6 Oct 2016, at 18:42, Anna Kalogirou <A.Kalogirou@leeds.ac.uk> wrote:
>>
>> Sorry for the delay, I was away from my desk all day today. I attach the two log files.
>>
>> Best, Anna.
>>
>> <log_file_mixed.txt><log_file.txt>
>
> OK great.  We can see that both options have quite a large room for improvement in the linear solver.
>
> The original code does ~6000 KSPSolve calls, but calls PCApply ~395000 times.  This tells me you're taking around 65 iterations per solve.  Which is probably quite a lot unless your problem is very stiff.
>
> The new code (mixed system) is worse, you do only ~2000 KSPSolve calls, but call PCApply almost ~3000000 times, or around ~1500 iterations per solve.  This is terrible :).
>
> What preconditioning, if any, are you using for these solves (in both cases?).  As Colin says, we need to figure out what the linear system looks like to choose an appropriate preconditioner.
>
> Cheers,
>
> Lawrence
>
>

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