[CIG-SHORT] Change in dt means new Jacobian

[Matthew Knepley]

On Fri, Sep 14, 2012 at 1:53 AM, Birendra jha <bjha7333 at yahoo.com> wrote:

> Dear developers
>
> I simplified my problem setup to see if no. of KSP iterations goes down.
> There are 46552 nodes, 42525 hex elements in a box.  In this very simple
> setup, both ASM and ML preconditioner takes ~90 iterations for convergence.
> Attached are the cfg files and stdout from LU and ML preconditioners. ASM
> stdout is not attached.
>

Something in your setup is causing the problem to be nearly or actually
singular. Its either bad elements in
the mesh, or an inconsistent boundary condition I think.


> Why does the run with LU crash? I just used following 2 lines to use LU:
> [pylithapp.petsc]
> pc_type = lu
> Is it incorrect?
>

This is interesting. Can you run in the debugger --petsc.start_in_debugger
and get a stack trace?

  Thanks,

     Matt


> For both ASM and ML, the solution looks correct in Paraview. It's just the
> time taken in integrating residual that I would like to reduce.
>
> Another question: when Pylith is running on a single multicore machine,
> can it use OpenMPI instead of MPI (I am assuming it's using MPI by default)?
>
> Thanks and regards
> Birendra
>
> --- On Tue, 9/4/12, Brad Aagaard <baagaard at usgs.gov> wrote:
>
> > From: Brad Aagaard <baagaard at usgs.gov>
> > Subject: Re: Change in dt means new Jacobian
> > To: "Birendra jha" <bjha7333 at yahoo.com>
> > Cc: cig-short at geodynamics.org
> > Date: Tuesday, September 4, 2012, 7:59 PM
> > On 09/03/2012 08:54 PM, Birendra jha
> > wrote:
> > > 3. How do I utilize multiple cores on a single machine?
> > Sorry if this
> > > question is already answered somewhere. I found
> > instructions on
> > > running parallel using a batch system but don't know
> > how to run on 1
> > > node and use multiple cores. Does this require
> > re-building Pylith?
> >
> > To run in parallel all you have to do is add the command
> > line argument --nodes=NUM_CORES. You do not need to
> > rebuild.
> >
> > > 4. For HDF5 output, is it correct that the I have to
> > wait until
> > > finish to get the xmf file which is needed to load h5
> > files in
> > > Paraview? Manual says "This file is written when PyLith
> > closes the
> > > HDF5 file at the end of the simulation".
> >
> > The Xdmf file is written when PyLith closes the HDF5 file at
> > the end of a simulation. There is a python script included
> > with PyLith called pylith_genxdmf that will generate the
> > Xdmf file given an HDF5 file. This is handy if a simulation
> > did not finish or you add additional fields to an existing
> > HDF5 file. Generating the Xdmf file in the middle of a
> > simulation can work but it is risky because the HDF5 file
> > can get corrupted if multiple processes try to access the
> > file simultaneously.
> >
> >   pylith_genxdmf --file=HDF5_FILE
> >
> > Brad
> >
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>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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