Symbolic Timing Simulation Using Cluster Scheduling

We recently introduced symbolic timing simulation (STS) using data-dependent delays as a tool for verifying the timing of fullcustom transistor-level circuit designs, and for the functional verification of delay-dependent logic. While STS leverages efficient symbolic encodings to yield huge gains over conventional simulation methodologies, it still suffers from a problem known as

event multiplication

. We discuss this problem and present an event-list management technique based on event-clusters, and a new simulator which utilizes this technique. Finally, we demonstrate substantial speedups on a wide range of test cases, including exponenti alimprovement on a simple logic chain.