Right now, at least in the EM code, a lot of things are being created on the startup of the Fields object. Really, the biggest thing is that the model be saved with the fields. All other operators can be lazily created when they are called, not everything need be done on the startup. The creation of a fields object can be quite slow if a mesh is large simply because all of these operators are being created (even if we aren't going to use them). This is a bit related to the refactoring happening in #672, but might be addressed in a follow up pr.
Right now, at least in the EM code, a lot of things are being created on the startup of the Fields object. Really, the biggest thing is that the model be saved with the fields. All other operators can be lazily created when they are called, not everything need be done on the startup. The creation of a fields object can be quite slow if a mesh is large simply because all of these operators are being created (even if we aren't going to use them). This is a bit related to the refactoring happening in #672, but might be addressed in a follow up pr.