dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sun, Oct 07, 2012 at 01:44:19PM +0100, Garth N. Wells wrote:
> Thanks to good work by Chris Richardson, support for the XDMF output
> format with HDF5 data storage is available in the development version
> of DOLFIN. HDF5 must be installed ('apt-get install
> libhdf5-openmpi-dev' or 'apt-get install libhdf5-mpich-dev' for
> Debian/Ubuntu users) to use it. To write to an XDMF file, just do
>
>    file = File("foo.xdmf")
>    file << u
>
> XDMF files can be read by ParaView, and have the following advantages
> over the VTK format:
>
> - All output data is stored in a single file (even in parallel),
> rather than the (#num_time_steps x #num_processes) files for VTK XML
> files
>
> - For Functions, the Mesh is not stored at every time step. At present
> the Mesh data structure is hashed to detect changes, with a new Mesh
> written to file only when a change is detected. This may change in the
> future.
>
> - Output files are much small than uncompressed VTK files
>
> - Writing output files is faster (about 5x for meshes, at present)

Great!

> Please try it out and report any issues. Since HDF5 is an optional
> dependency, no demos have been set to use XDMF yet.

Except for this one?

  demo/undocumented/hdf5

> Some options for
> adding XDMF output to the demos are
>
> 1) Fall-back to VTK/PVD format if XDMF is not available; or
> 2) Add support for writing ASCII data in the XDMF file if HDF5 is not available.

It would be easy to make File.cpp choose VKT (pvd) if XDMF is not
available. I haven't tried the XDMF output yet, but if it works well I
don't see why we shouldn't make it the default output format and
change to XDMF in all the demos, with automatic fallback to VTK.

--
Anders