The simulation library SIM

The BPSIM library is an extension of the simulation library SIM . SIM adopts the method of Discrete Event Simulation . With this approach, the components of the model consists of events, which are activated at certain points in time and in this way affect the overall state of the system. The simulation library SIM consists of the following C++ classes ([1]):

• simulation, the class simulation  keeps the scheduler, that controls which event should be activated. It employs a calender of events and repeatedly extracts the event, that should execute. A clock  is kept, so it can be determined which event becomes the current. Furthermore, it maintains a conditional list  where events can be put that could not execute but may be executed in the future;
• event, events  represent the dynamic objects in the system. They have a temporary existence and unique characteristics. An event in the simulation should be derived from the abstract class event and be given functionality by overwriting its function operator . The function operator is the member function that is called by the simulation when the event is activated;
• entity, an entity  represents a process  in the system, it combines several related events into one process. As with the event class, the entity class is abstract. A process should be derived from it and be given functionality by overwriting its function operator;
• generator,   a collection functions that permits a variety of random streams and probability distributions for generating random numbers;
• resource, a resource  represents a passive object in the model, that is used by an event;
• queue, a queue  maintains queued events, that are, for example, waiting for a resource to become free;
• histogram, the class histogram  makes it possible to gather and print samples. For example, information about queue sizes and waiting times can be gathered;
• analysis, the class analysis  makes it possible to analyze a histogram. Members for confidence intervals, fitting curves and probility distributions and for analyzing steady state behavior are provided.