Gateways: a technique for adding event-driven behavior to compiled simulations

The gateway technique is a method for switching segments of code into and out of the instruction stream. When added to the straight-line code generated by a compiled simulator, gateways can be used to enhance the performance of the generated code by switching only those segments of code that actually need to be executed into the instruction stream. The convergence algorithm is an oblivious compiled code algorithm that can be used with many different types of circuits, including cyclic asynchronous circuits. In its oblivious form, the convergence algorithm provides only modest gains in performance over interpreted event-driven simulation, but with the addition of gateways, the performance of the algorithm increases significantly. Experimental data shows that with gateways, the convergence algorithm runs in about 1/5th the time required for an interpreted event-driven simulation. Additional work has been done to reduce the amount of code generated by the convergence algorithm, and to enhance the locality of the code to improve its performance on machines with caches. When used with a multi-delay algorithm, gateways allow simulations to be performed in 1/3 the time required by interpreted simulations. Gateways also allow zero-delay simulations to be more responsive to the activity rate of the circuit, and allow event driven simulations to outperform levelized compiled code when the activity rate of the circuit falls below 13%.<
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