dolfin team mailing list archive

[Johan Hake <hake.dev@xxxxxxxxx>]

On 10/07/2012 02:44 PM, 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.

Nice! How did you hash the mesh data? Just num_vertices/num_cells or a
more detailed one. Would be nice with a robust and fast routine for such
a computation.

> - 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.

I also see that there are no File::Type corresponding to HDF5 or xdmf.
Is this intentionally? Even if dolfin has not been compiled with HDF5
support we could include the enum and then issue an error?

Johan

> Garth
> 
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