Improved file handling for discrete-event models with event cancellation

Discrete-event models written in general-purpose simulation languages often run slowly because of the ways in which these languages file and search for events. For example, files may regularly be searched starting from the wrong end, newly created events may be assumed to occur later than events already filed, next events for particular entities may not be directly accessible, and events that must be cancelled may re quire extensive searches. Improved filing procedures include automatic selection of backward or forward searching, main tenance of a matrix of next events for particular entities, and saving of events in a FIFO file until their occurrence times near. In the case of a GASP IV model of electrical power generating systems, improving file handling reduced its run time by an order of magnitude. This model involves frequent creation and cancellation of events as units are turned on and off. Furthermore, the operator must select the particular units to be started or removed from operation on the basis of cost and other factors.