A 3D example of KSPSolve?

[Barry Smith]

  NO, NO, don't spend time stripping your code! Unproductive

  See the manul pages for PetscLogStageRegister(), PetscLogStagePush() and 
PetscLogStagePop(). All you need to do is maintain a seperate stage for each
of your KSPSolves; in your case you'll create 3 stages.

   Barry

On Fri, 9 Feb 2007, Shi Jin wrote:

> 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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