dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

On 24/08/11 08:07, Anders Logg wrote:
> On Wed, Aug 24, 2011 at 07:22:53AM -0400, Garth N. Wells wrote:
>>
>>
>> On 24/08/11 03:50, Anders Logg wrote:
>>> What is the plan for XMLLocalMeshData (using the DOM interface) vs
>>> XMLLocalMeshDataDistributed (using the SAX interface)?
>>>
>>
>> Both for the time being.
>>
>>> Reading boundary indicators is currently failing with
>>>
>>> RuntimeError: *** Error: Inconsistent state in XML reader: 6.
>>>
>>> Should this be fixed in XMLLocalMeshDataDistributed or is the plan to
>>> replace it with XMLLocalMeshData?
>>>
>>
>> In XMLLocalMeshDataDistributed.
> 
> Could you elaborate? The functionality for reading and distributing
> boundary markers (in parallel) is currently broken and we want to fix
> it. But we need to know more about the design. I don't want to fix
> something if you decide to break it 5 min later.
> 

It never 'properly' worked in parallel. There were some messy ad hoc
changes made on top of functions that were planned for overhaul. I made
clear before this that parallel functionality was being sorted out (it's
not just in io, but also partitioning, etc), so the fact that it's not
working now should not be a surprise.

There is a lot of missing functionality is parallel, so patience is
required to get things done properly.

> Should we continue to use libxml2? Why not use the DOM parsing all the
> way?
> 

Because I'm inclined to keep SAX parsing for meshes since meshes are the
most likely to be created externally, and need to be scalable for
reading. Other objects (e.g., vectors) are likely to be created and
written by DOLFIN, so will eventually use parallel HDF5 for scalable
parallel io.

> What is the difference between XMLLocalMeshData and
> XMLLocalMeshDataDistributed etc.
> 

Initially I planned to use DOM for all, but as outlined above decided
after some testing to retain SAX for meshes (but update to SAX2, since
the libxml2 SAX parser is deprecated and has memory leaks). Hence,
XMLLocalMeshData uses DOM and XMLLocalMeshDataDistributed uses SAX. So
far I've kept the DOM version since it's easy to code and could be
useful when reading non-distributed meshes on each process (which may
differ on different processes).

Garth

> --
> Anders
>