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Oh we do know, but what we don't know is the structure of your program, the way you want the engine to communicate with the GUI, etc., etc.

MUI vs intuition speed difference is negligible in your case - you are going to waste most CPU time passing and parsing information in text format from your cli command. This is where you are going the wrong way - having the engine in a separate cli application is a mistake. The GUI and the engine should be integrated into one application.