Since a unary resource can only process one activity at a time, all activities requiring the same unary resource must be totally ordered in a solution. As a result, in any solution to a problem that includes a unary resource, each unary resource defines a directed path through all the activities requiring it.

Between each pair of consecutive activities, some cost may be incurred to switch the resource from processing the first activity to processing the second. These costs may be related to modifications to the resource that require manpower, material, and energy, such as adjusting or purging a machine.

In Scheduler Engine, transition cost is defined as the cost between two immediately successive activities in the sequence constraint of a unary resource. In addition, Scheduler Engine lets you define a setup cost for the activity that starts the usage of the resource and a teardown cost for the activity that ends the usage of the resource.

The transition cost object instance of IlcTransitionCostObject can be added to a unary resource with a sequence constraint using the function IlcUnaryResource::addNextTransitionCost or IlcUnaryResource::addPrevTransitionCost. The transition cost will be taken into account by the propagation.

The transition cost can be variable or constant. By constant we mean that it only depends upon the precedence relationship between two activities. By variable we mean that the evaluation of the transition cost depends upon current knowledge about the other variables and constraints involved. If it is variable, the transition cost object must define its minimal and maximal value given the current knowledge about the sequence.

Scheduler Engine associates an integer transition type to each activity. The accessors are the functions IlcActivity::getTransitionType and IlcActivity::setTransitionType. They allow you to define instances of IlcTransitionCostObject from integer tables where the rows and columns are indexed by the transition types.

See Also

IlcMakeTransitionCost, IlcTransitionCostObject, IlcTransitionTable, IlcUnaryResource, Transition Cost (Setup and Teardown Costs) In Scheduler Engine