Pass the param dict directly to the backend?

[leofang]

Currently we maintain, effectively, 4 distinct dicts:

1. https://github.com/leofang/ptycho_gui/blob/b64326d7d0db5f05bda684a55f295bf1fdeb57e2/nsls2ptycho/core/ptycho_param.py#L23
2. An instance of the above Param() class here: https://github.com/leofang/ptycho_gui/blob/b64326d7d0db5f05bda684a55f295bf1fdeb57e2/nsls2ptycho/ptycho_gui.py#L104-L108
3. configparser: https://github.com/leofang/ptycho/blob/b0b39bd849ad65842659e29dc446f9629fa1433e/utils.py#L8
4. The backend ptycho_trans class https://github.com/leofang/ptycho/blob/b0b39bd849ad65842659e29dc446f9629fa1433e/ptycho_trans_ml.py#L79

This has caused a significant headache every time we want to pass new attributes from the fronted to the backend: We have to update all the four files above plus https://github.com/leofang/ptycho/blob/master/recon_ptycho_gui.py to get it work, which is too tedious from the maintenance point of view.

The goal is to maintain a single dictionary across both frontend and backend. Steps to resolve this are:

• Instantiate the backend ptycho_trans class directly in the frontend, and dump its attributes to disk as before
• Eliminate the intermediate Param class
• Investigate the possibility of making the instance in-memory for the backend to reuse
• Eliminate the usage of configparser

[leofang]

Instantiate the backend ptycho_trans class directly in the frontend, and dump its attributes to disk as before

This will do:

from nsls2ptycho.core.ptycho.ptycho_trans_ml import ptycho_trans
pty = ptycho_trans(None)

[leofang]

We needed to dump the dict as a text file for the backend to read because otherwise the backend had no way to tell the working directory (and shm_name):
https://github.com/leofang/ptycho_gui/blob/b64326d7d0db5f05bda684a55f295bf1fdeb57e2/nsls2ptycho/ptycho_gui.py#L504-L505
But, if we let the Qt thread to define a few environmental variables at the start time of the backend, this need will be eliminated. Then, we can consider passing around a ptycho_trans instance in-memory.

[leofang]

Problems:

1. some bugs due to conflicting attributes showed up
2. when the reconstruction is done, has to instantiate a new param in the GUI (now = ptycho_trans) to avoid potential conflicts -> more complicated than I thought
3. with shared memory, how to address the problem above? close the existing segment and open a new one?

This effort is currently in this branch: https://github.com/leofang/ptycho_gui/tree/refactor