Field serialisation utilities

[awnawab]

To enable testing of standalone components, and to aid debugging, we wish to add basic I/O functionality that allows fields to be easily saved to and loaded from file. Importantly, this functionality is not intended to replace the model I/O, but rather simply to enable model/state serialisation. In terms of the I/O format to be used, my first instinct is to just use HDF5.

[awnawab]

@dareg, @pmarguinaud I would really appreciate your input on this, especially on the choice of I/O format. Many thanks! 🙏

[dareg]

Hello,

Maybe it should belongs to a completely separate "project" or repository inside the ecmwf-ifs github organisation, since it's not a core functionality of field_api. I think it would be better to not grow field_api too much and to try to keep it on point as much as possible.

So we could have repositories like field_api_serialisation_hdf5 or also field_api_serialisation_netcdf if we want to experiment with other formats (but I think HDF5 is a good choice, it's common, works fine, and there's usually tools at hand to read it).

[dareg]

On the other hand, I guess it would be fine if the implementation was self-contained, like in a single file or a set of files and let it be completely optional (so we would still be able to compile field_api without any installation of HDF5).

[awnawab]

Yes I agree, the I/O utils should be both cleanly separated and optional (off by default). Thanks for the feedback! 🙏