Run generator in serial on manager

[shuds13]

This is proof-of-principle for running the generator in-place on the manager.

• The generator can be provided as a function or a class (see generators/base.py)
• Giving resources to the generator has not yet been implemented.
• Tested with test_ax_generators.py

This represents one possible approach (pros/cons)

• Allows pass by reference
• Reduces communications
• Easier to debug generator issues (compared to using a thread)
• Easy to support using a gen directory (compared to using a thread)
• Works naturally with a class generator.
• Use of finalize routine seems intuitive in place of final_gen_send.
• con: Requires moving from current persistent style generator
• con: Will block on long running gen.

[AngelFP]

Hi @shuds13, nice progress, this looks really promising. I have a couple of questions:

• With this implementation, it looks like the Optgen is really the object in charge of carrying out the whole optimization (asking the generator for trials and launching them for evaluation). Within optimas, this is basically what the Exploration is supposed to do. So, I was wondering, could the run method of Optgen be moved to the Exploration (with another name such as _libe_run, as run is already taken), and then we set gen_specs['gen_f']=exploration._libe_run? This could also be done in a separate PR. Just wondering if passing a class method as gen_f is possible (I think @jlnav mentioned this last meeting). I got this wrong, nevermind.
• Regarding the resources, the main thing we need is to be able to dedicate a GPU to the generator (or the manager, now). Is that something that can be done with this new approach?

[shuds13]

• Regarding the resources, the main thing we need is to be able to dedicate a GPU to the generator (or the manager, now). Is that something that can be done with this new approach?

My intention is that it will work just as it does now (as you say the manager will be assigned resources). I just haven't yet got around to ensuring the resources part works.