Scheduler - Operation Theater Module

The module uses a library named Optaplanner for scheduling theater activities. It’s an open source constraint satisfaction solver written in Java. We can model the theater planning activity as a constraint satisfaction problem (CSP) and use Optaplanner to get a somewhat optimal solution in a given amount of time. As you might know, CSPs are  considered to be either NP-complete or harder.

Let’s start with a few definitions.

Constraint satisfaction problem – a problem with a limited set of resources, and constraints on possible paths to a solution. A solution needs to satisfy the given constraints and employ available resources.
NP-completeness – the abbreviation NP means Nondeterministic Polynomial time. We’ll need to go way out of our topic to describe what each of those terms mean exactly, so let’s get a high-level idea. Simply put, NP-complete means the following;

• It’s easy to verify a given solution of such a problem, in a reasonable amount of time.
• We don’t know an efficient method to get such a solution.

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.

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.