Re: [Libmesh-devel] Read in GMV files

[Derek G. <fri...@gm...>]

Sigh... that's what I was afraid of.

Damn... what a huge pain.

For some reason I can't get the same large solutions to solve on my
big Solaris machine here... they all segfault at some point.

Damn, Damn, Damn, Damn, Damn.

Thanks for the quick response...

Derek

On 7/9/07, John Peterson <pet...@cf...> wrote:
> Derek Gaston writes:
>  > John,
>  >
>  > Sorry to dredge up an old email... but I'm wondering if you have any
>  > idea how much error there is in this process?  Are the full double
>  > precision numbers being output to the GMV file and read back in?
>
> AFAIK all our GMV files are written single precision.  So, you only
> read in GMVs if it's your last resort ;-( I was able to get semi-good
> postprocessed flux and volume integrals (say within 5-10% of true
> value) but you can't use it for anything like convergence plots,
> unfortunately.
>
>  > I'm trying to re-use some runs I made last year... I have xda's for
>  > the mesh, and xdr's for the solutions... but for whatever reason those
>  > xdr's are corrupt (I remember that they were corrupt when they first
>  > came out too...).  I also have gmv's and plt's of the same junk.  I
>  > would _love_ to re-use these solutions as they are on millions of
>  > elements (took a long time to get, even on lonestar).  But I'm going
>  > to be using them to drive error and indicator calculations so I need
>  > them to be precise.
>  >
>  > Thanks,
>  > Derek
>  >
>  > On 6/5/07, John Peterson <pet...@cf...> wrote:
>  > > Hi,
>  > >
>  > > It's possible to read in a GMV file and solutions.
>  > > Sample code:
>  > >
>  > > {
>  > >   Mesh mesh(dim);
>  > >   GMVIO gmvio(mesh);
>  > >   gmvio.read("meshfile.gmv");
>  > > }
>  > >
>  > > If there were solution fields in the GMV file they
>  > > were read in as well and are now stored in the GMV
>  > > object.  Suppose you later created an EquationSystems
>  > > object based on this mesh:
>  > >
>  > > {
>  > >   EquationSystems es(mesh);
>  > >
>  > >   TransientLinearImplicitSystem & heat_system =
>  > >    es.add_system<TransientLinearImplicitSystem> ("HeatSystem");
>  > >
>  > >   heat_system.add_variable ("T", FIRST);
>  > >
>  > >   es.init();
>  > > }
>  > >
>  > > Then, you can copy the solution you read in
>  > > from the GMV file to the EquationSystems object:
>  > >
>  > > {
>  > >   gmvio.copy_nodal_solution(es);
>  > > }
>  > >
>  > > I did it in stages like this because you can't initialize the
>  > > EquationSystems without the mesh, and you can't easily put the
>  > > solution data into the EquationSystems object before it has been
>  > > initialized.
>  > >
>  > > Note that there isn't much information stored in a GMV file: only
>  > > nodal (or cell, which I didn't support yet) data values, so this
>  > > feature is limited to reading in linear, Lagrange elements (sorry
>  > > Roy!).
>  > >
>  > > If you wrote out a quadratic solution to a GMV file, it was probably
>  > > written out as linear sub-elements, so this is what will be read back
>  > > in, not your nice original quadratic solution.  It will also probably
>  > > completely break on non-conforming (AMR) GMV files, I haven't even
>  > > tested that yet.
>  > >
>  > > I mainly wrote this was to be able to post-process uniform GMV files
>  > > for which I forgot to also write out the xda files.  I hope it will
>  > > be useful for that, and maybe other stuff.
>  > >
>  > > -John
>  > >
>  > >
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