An open-source framework for solving shop scheduling problems in manufacturing environments

Scheduling problems refer to the decision-making process of allocating tasks to resources, usually scarce and in high demand, to optimize different performance measures. We consider the class of shop scheduling problems arising in the context of manufacturing systems, which are often NP-hard and challenging to solve. Exact methods have limitations in finding optimal solutions in reasonable computation times, even for instances of moderate size. Therefore, in real-life production environments, finding high-quality solutions is often satisfactory, even if they are not optimal. We contribute to the solution of shop scheduling problems with the design and implementation of the SSP-3M framework, oriented by three main guidelines: versatility, extensibility, and independence of the optimization method. These characteristics reduce the gap between scheduling theory and practice in real-life environments and improve the integration of the scheduling framework with other process planning or functions such as Computer-aided Process Planning, Advanced Planning and Scheduling, Integrated Process Planning and Scheduling, and Computer Integrated Manufacturing. The problem and solution representations adopted in our framework design make it possible to handle six shop scheduling problem variants, illustrating its versatility: job shop, flow shop, permutation flow shop, generalized flow shop, flexible flow shop, and flexible job shop. SSP-3M is open-source and can be used by any interested party. Our experimental evaluation shows that it can successfully be integrated with external optimization methods. We claim that SSP-3M is a good choice for companies that need free and quick-to-develop solutions to shop scheduling problems.