[petsc-users] no decrease in iteration counts of KSPCG during time stepping

[Mark Adams]

On Sat, Dec 27, 2014 at 5:00 AM, Alp Kalpalp <alpkalpalp at gmail.com> wrote:

> Hi,
>
> I implemented a newmark time stepping algorithm without using TS
> structure. I am following ex59 about PCBDDC.
>
>
use TS


> ComputeMatrix
> ComputeKSPBDDC
>
> for // a time loop
> {
> Compute RHS
> KSPSolve
> GatherResults
> MoveToNextTS
> }
>
>
> However, when I watch the iteration counts of KSPSolve they do not
> decrease signicantly..Decrease was around 5%.
>
> So I have some problems;
>
> 1-) I guess currently, factorization is not taking place for each time
> step in my code. Ok this is expected. But I wonder whether Kspsolve stores
> the Krylov subspace vectors and reuse them for the next time step.
>
>
No.  Certainly not by default.


> 2-) PCBDDC uses KSPCG and AFAIK petsc doesnot have preconditioned
> conjugate projected gradient (PCPG). Is it possible to simulate PCPG
> iteration in some way?
>
>
KSP has a PC object and all methods use it AFAIK.


> Thanks,
>
>
>
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