A 3D example of KSPSolve?

[Matthew Knepley]

You really have to give us the log summary output. None of the relevant
numbers are in your summary.

 Thanks,

   Matt

On 2/9/07, Shi Jin <jinzishuai at yahoo.com> wrote:
>
> Dear Barry,
>
> Thank you.
> I actually have done the staging already.
> I summarized the timing of the runs in google online
> spreadsheets. I have two runs.
> 1. with 400,000 finite elements:
> http://spreadsheets.google.com/pub?key=pZHoqlL60quZeDZlucTjEIA
> 2. with 1,600,000 finite elements:
> http://spreadsheets.google.com/pub?key=pZHoqlL60quZcCVLAqmzqQQ
>
> If you can take a look at them and give me some
> advice, I will be deeply grateful.
>
> Shi
> --- Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> >
> >   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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