Ernst G. Ulrich
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Event manipulation for discrete simulations requiring large numbers of events
The event-manipulation system presented here consists of two major parts. The first part addresses the familiar problem of event scheduling efficiency when the number of scheduled events grows large. The second part deals with the less apparent problem of providing efficiency and flexibility as scheduled events are accessed to be executed. Additional features and problems dealt with include the proper handling of simultaneous events; that certain events must be created, scheduled, and executed at the same points in simulated time; that infinite loops caused by the concatenation of such “zero-time” events are possible and must be diagnosed; that maintaining various event counts is practical and economical; and that a capability for handling “time-displaceable” events is desirable and possible.
Exclusive simulation of activity in digital networks
A technique for simulating the detailed logic networks of large and active digital systems is described. Essential objectives sought are improved ease and economy in model generation, economy in execution time and space, and a facility for handling simultaneous activities. The main results obtained are a clear and useful separation of structural and behavioral model description, a reduction of manual tasks in converting Boolean logic into a structural model, the elimination of manual processes in achieving exclusive simulation of activity, an event-scheduling technique which does not deteriorate in economy as the event queue grows in length, and a simulation procedure which deals effectively with any mixture of serial and simultaneous activities. The passage of time is simulated in a precise, quantitative fashion, and systems to be simulated may be combinations of synchronous and asynchronous logic. Certain aspects of the techniques described may be used for the simulation of network structures other than digital networks.
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