Re: [Libmesh-users] Read/write solution vectors

[Roy S. <roy...@ic...>]

On Mon, 6 Nov 2017, Manav Bhatia wrote:

> I see that this is all done using XDR. Is there a particular reason
> to prefer XDR as opposed to .exo?

Support for adaptive refinement hierarchies (IIRC we still have to
"flatten" a mesh to output Exodus), higher p (I believe Exodus only
supports up to second order elements), and more element types
(anything we output to Exodus ends up getting interpolated onto a
Lagrange basis, basically).

Oh, and support for parallel output, though we instead can do that in
an Exodus-friendly way via Nemesis.

> Can XDR be used for data visualization? 

Not directly.  I usually save XDR from simulations to use for restarts
and/or postprocessing, then run a "meshplot" utility to convert into
another format when I want to visualize.

> Do you know if someone has implemented a read function from .exo
> files?

Yes; see "copy_nodal_solution()" and "copy_elemental_solution()".

> Given that I am already using it for post processing
> (visualization in Paraview), it would be good to use the same data
> for other computations, as opposed to writing XDR files in
> addition. 

I definitely wouldn't write XDR in addition unless you have to; disk
is slow.  Writing it instead might be worthwhile though.
---
Roy