[Gmsh] Optimising binary .msh format

[Michael Lange]

Hi,

I am trying to optimise the performance of the current file reader for 
binary .msh files in PETSc by utilising the element grouping described 
in the binary format (see 
http://www.geuz.org/gmsh/doc/texinfo/#MSH-binary-file-format). However, 
using a recent version of Gmsh (version 2.9.3, with options: -3 -bin), 
the generated .msh files contain a header + binary entry pair for each 
element in the mesh, instead of two groups of same-type elements (volume 
and surface). This unfortunately prevents me from using efficient bulk 
reads to speed up file I/O and hinders performance when reading large 
meshes on certain HPC architectures.

Is there any way to enable this type of element grouping in the binary 
mesh file generation? Am I missing an option by any chance, or does this 
require significant code changes?

Thanks,

Michael Lange