std::complex

[ax3l]

Although not part of the openPMD standard yet, handling of types for std::complex< T > with float, double and long double could be investigated.

Keep in mind:

• be compatible with h5py: http://docs.h5py.org/en/latest/faq.html
• ADIOS1 support
• ADIOS2 support
• openPMD-standard issues: Complex Numbers: define touple of two as integral? openPMD-standard#29 Record Components of Struct openPMD-standard#144

[CFGrote]

yep, i need this for wavefront data. any progress here?

[ax3l]

We haven't started working on this yet. I defend in a week from now, little time to look into this right now but maybe you can store it interleaved like we do it for the thetaMode geometry? Of course, thoughts and PRs are welcome as well :)

[CFGrote]

ok, interleaving should work. good luck for next week!

[ax3l]

For the interested reader of this issue that would like to work on this:
the first step is to define new data types in include/openPMD/Datatype.hpp

Then, e.g. starting with HDF5, one defines new types in the backends such as src/IO/HDF5/HDF5IOHandler.cpp. For HDF5 in particular, we want to be compatible with h5py's representation of types [1] [2] (more general info on compound types).

In ADIOS1 (https://github.com/ornladios/ADIOS/search?q=complex&unscoped_q=complex) as well as ADIOS2, complex data types are supported by default: https://adios2.readthedocs.io/en/latest/components/components.html#variables-data-types

In JSON we probably just write a real-imaginary tuple.

[ax3l]

Implementation started in #639

[ax3l]

The implementation is mainly done, just waiting for a new ADIOS2 release to be tagged. We contributed support for complex types in attributes: ornladios/ADIOS2#1908

[ax3l]

Standardization agreed upon and documented here: openPMD/openPMD-standard#29 (comment)

#639 adds the implementation in the API and will be shipped with the next release, openPMD-api 0.12.0.