Lookup tables for post-processing simulation data

[nvaytet]

In #50 , it was suggested to re-introduce an old feature from version 1 which allowed to compute EOS quantities or opacities from primary variables in the simulation (e.g. density and temperature).

The primary aim for this is to save disk space, by not storing the opacities in the outputs, as storing many of those quantities can rapidly grow output size.

The work in #50 is also very specific to ISM physics, but it seems that other areas of applications also need something similar.
For example, a cooling table is used for galaxy formation and evolution.

For this, they usually save a copy of the cooling table in each output, and this is ok as long as the file is small compared to the total size of the snapshot.

What about very large tables? Do they exist?