dolfin team mailing list archive

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

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)

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

Garth