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The best-known characteristic of NP-complete problems is that we don’t have a fast way to solve them. All current methods grow exponentially more complex as the size of the problem grows.
You already know that theater scheduling is a CSP. What else are CSPs? Well, think Think about creating timetables in a university. Or scheduling nurses in a hospital. Planning car assembly lines. Investment portfolio optimization. Cutting steel sheets in an optimal manner. All of these are constraint satisfaction problems. And planning problems. They have goals that they wish to optimize and limited resources under constraints. You can refer the documentation of Optaplanner for a good description of them.
The module considers the theater's open hours, duration of each surgery and current availability of theater locations when coming up with a schedule. One particular point to remember is that unless a surgery is marked as finished, it will be rescheduled when the scheduler is run.