Is there an inherent size limit for plain text .xdmf files (ASCII encoding) containing both the metadata and heavy data? I noticed that in this case the Xdmf3ReaderT crashes even for simplistic meshes if the number of elements is larger than about 500k. The files are most likely valid, they have been created by established software and show no abnormalities during inspection. Files with a smaller number of elements can be opened without any problems.