HDF5: Chunking

[ax3l]

Our HDF5 backend does not yet implement proper chunking.

Note: we should stay with fixed size data spaces nonetheless for performance.

References:

• https://support.hdfgroup.org/HDF5/doc/Advanced/Chunking/
• https://support.hdfgroup.org/HDF5/faq/parallel.html

Pitfalls:

• Resizable datasets used always ComputationalRadiationPhysics/libSplash#133
• HDF5: Field "Kinks" with FreeFormula ComputationalRadiationPhysics/picongpu#2841

libSplash implementation:

• https://github.com/ComputationalRadiationPhysics/libSplash/blob/master/src/DCDataSet.cpp#L169-L170
• https://github.com/ComputationalRadiationPhysics/libSplash/blob/master/src/include/splash/core/DCHelper.hpp#L87-L104