A 3D example of KSPSolve?

[Shi Jin]

Thank you.
But my code has 10 calls to KSPSolve of three
different linear systems at each time update. Should I
strip it down to a single KSPSolve so that it is
easier to analysis? I might have the code dump the
Matrix and vector and write another code to read them
into and call KSPSolve. I don't know whether this is
worth doing  or should I just send in the messy log
file of the whole run.
Thanks for any advice.

Shi

--- Barry Smith <bsmith at mcs.anl.gov> wrote:

> 
>   Shi,
> 
>    There is never a better test problem then your
> actual problem.
> Send the results from running on 1, 4, and 8
> processes with the options
> -log_summary -ksp_view (use the optimized version of
> PETSc (running 
> config/configure.py --with-debugging=0))
> 
>   Barry
> 
> 
> On Fri, 9 Feb 2007, Shi Jin wrote:
> 
> > Hi there,
> > 
> > I am tuning our 3D FEM CFD code written with
> PETSc.
> > The code doesn't scale very well. For example,
> with 8
> > processes on a linux cluster, the speedup we
> achieve
> > with a fairly large problem size(million of
> elements)
> > is only 3 to 4 using the Congugate gradient
> solver. We
> > can achieve a speed up of a 6.5 using a GMRes
> solver
> > but the wall clock time of a GMRes is longer than
> a CG
> > solver which indicates that CG is the faster
> solver
> > and it scales not as good as GMRes. Is this
> generally
> > true?
> > 
> > I then went to the examples and find a 2D example
> of
> > KSPSolve (ex2.c). I let the code ran with a
> 1000x1000
> > mesh and get a linear scaling of the CG solver and
> a
> > super linear scaling of the GMRes. These are both
> much
> > better than our code. However, I think the 2D
> nature
> > of the sample problem might help the scaling of
> the
> > code. So I would like to try some 3D example using
> the
> > KSPSolve. Unfortunately, I couldn't find such an
> > example either in the
> src/ksp/ksp/examples/tutorials
> > directory or by google search. There are a couple
> of
> > 3D examples in the src/ksp/ksp/examples/tutorials
> but
> > they   are about the SNES not KSPSolve. If anyone
> can
> > provide me with such an example, I would really
> > appreciate it.
> > Thanks a lot.
> > 
> > Shi
> > 
> > 
> >  
> >
>
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> 
> 



 
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