1 Introduction As the size and complexity of digital circuits grows, so does need for logic simulation. Recent research has focused on compiled simulation because it provides substantially better performance than interpretive methods. In compiled simulation, a program is generated from the circuit to be simulated. Running this program, called a compiled simulator, then simulates the circuit. Compiled simulation executes much more rapidly than interpreted simulation because the overhead of tranversing and interpreting the data structure that describes the circuit is done only once, when the compiled simulator is created.

Two new techniques for compiled multi-delay simulation are presented, one which is event-driven and another which is based on the concept of levelized compiled simulation. Experimental results are presented which show a significant performance improvement for compiled event-driven simulation over interpreted event-driven simulation, although this improvement is somewhat less than would normally be expected. An analysis of both the compiled and interpretive simulators is presented that supports the experimental data. The effects of caching and locality of reference are presented for the compiled event-driven simulator. The performance enhancements for the non-event-driven technique are substantial, but this technique has the disadvantage of generating an enormous amount of code for some circuits. Suggestions for future research are also presented.

Object-oriented simulations in an object-oriented environment are easier to construct and maintain than conventionally programmed simulations. Unfortunately, they are also slower because of message passing and other runtime overhead. We have developed an automatic program transformer that solves the efficiency problem for a large class of simulation programs. It automatically constructs an efficient program from the inefficient simulation program and the objects it will receive as input. Depending on the object-oriented language used, and the application, the new program can be more than an order of magnitude faster than the original program. In this paper we describe the benefits of object-oriented simulation, our transformer, and how such dramatic speedups are possible. This research has been supported in part by NSF Contract No. MIP-8902764, and in part by Advanced Research Projects Agency, Department of Defense, Contract No. N0039-91-K-0138. Key Words and Phrases: Object-Oriented S...

LECSIM is a highly efficient logic simulator which integrates the advantages of event driven interpretive simulation and levelized compiled simulation. Two techniques contribute to the high efficiency. First it employs the zero-delay simulation model with levelized event scheduling to eliminate most unnecessary evaluations. Second, it compiles the central event scheduler into simple local scheduling segments which reduces the overhead of event scheduling. Experimental results show that LECSIM runs about 8-77 time faster than traditional unit-delay event-driven interpretive simulator. LECSIM also provides the option of scheduling with respect to individual gates or with respect to fan-out free blocks. When the circuit is partitioned into fan-out free blocks, the speed increases by a factor of 2-3. With partitioning, the speed of LECSIM is only about 1.5-3.4 times slower than a levelized compiled simulation.