Resources

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Scheduler provides several classes to represent resources. The class IloResource is the root class for all the resources managed in Scheduler. IloResource has two subclasses, IloStateResource and IloCapResource.

An instance of the class IloStateResource represents a resource of infinite capacity whose state can vary over time. Throughout its execution, each activity may require a state resource to be in a given state (or in any of a given set of states). Consequently, two activities may not overlap if they require incompatible states during their execution.

• IloDiscreteResource: An instance of IloDiscreteResource represents a resource of finite discrete capacity. Discrete means that capacity is defined to be a positive integer number. Capacity varies with time: at any time t, the capacity represents the number of copies or instances of the resource that are available; examples include the number of milling machines available in a manufacturing shop, or the number of bricklayers at work on a construction site.
Each activity may require some amount of the resource capacity, for example, one milling machine or three bricklayers. This requirement is represented by resource constraints. Propagation of resource constraints entails an update of the earliest and latest start and end times of activities.
• IloUnaryResource: An instance of IloUnaryResource represents a resource whose capacity is one. An instance of IloUnaryResource is either occupied or free. No more than one activity can be executed at a given time. The class IloUnaryResource is a subclass of IloDiscreteResource.
• IloDiscreteEnergy: An instance of the class IloDiscreteEnergy is divided into time buckets (for example, minutes, hours, months, years) that contain a certain amount of energy (for example, watt-hours or human-months) that can be made available over those intervals. The available energy is used by the activities defined on the resource, and as a consequence capacity constraints on the discrete energy resource use energy rather than capacity.
• IloReservoir: An instance of IloReservoir represents a resource that can be dynamically replenished by producing activities. The capacity of an instance of IloReservoir can be simultaneously required and provided by activities. This class can be used to model situations in which certain types of activities consume capacity from the reservoir, while others produce capacity.
A reservoir must not overflow its maximal capacity or underflow its minimal capacity.
• IloContinuousReservoir. An instance of IloContinuousReservoir represents a resource which activities can either fill or empty in a continuous and linear process between the start and the end of the activity. If the duration of the activity is null, the filling (or emptying) process is instantaneous (so not continuous). The maximum and minimum levels of a continuous reservoir can vary over time.