Distributed simulation of VLSI systems via lookahead-free self-adaptive optimistic and conservative synchronization

The paper presents a novel protocol for parallel and distributed simulation of VLSI systems. It is novel in two aspects: first, it combines optimistic and conservative synchronization methods, allowing processes to self-adapt for maximal utilization of concurrency. Second, it does not require any application-dependent information like lookahead, which in many cases is unknown, zero, or difficult to automatically obtain from a design in a hardware description language. All these features make it very convenient and practical, extending the class of applications to at least all VHDL circuits, including delta cycle. The proposed protocol has been implemented and used for VHDL simulation. Experimental results on several large VHDL circuits (between 1411 and 14704 processes) have shown promising linear speedups. We also observed that the dynamic synchronization, in which processes automatically adapt to optimistic or conservative behavior, follows closely or finds a very good configuration. This protocol may have a strong impact for mixed-signal circuit simulation, where digital parts may be optimistic and heavy-state analog parts, conservative.