Efficient manipulation of Boolean functions is an important component of many computer-aided design tasks. This paper describes a package for manipulating Boolean functions based on the reduced, ordered, binary decision diagram (ROBDD) representation. The package is based on an efficient implementation of the if-then-else (ITE) operator. A hash table is used to maintain a strong carwnical form in the ROBDD, and memory use is improved by merging the hash table and the ROBDD into a hybrid data structure. A memory funcfion for the recursive ITE algorithm is implemented using a hash-based cache to decrease memory use. Memory function efficiency is improved by using rules that detect. when equivalent functions are computed. The usefulness of the package is enhanced by an automatic and low-cost scheme for rec:ycling memory. Experimental results are given to demonstrate why various implementation trade-offs were made. These results indicate that the package described here is significantly faster and more memory-efficient than other ROBDD implementations described in the literature.
The COSMOS simulator provides fast and accurate switch-level modeling of MOS digital circuits. It attains high performance by preprocessing the transistor network into a functionally equivalent Boolean representation.This description, produced by the symbolic analyzer ANAMOS, captures all aspects of switch-level networks including bidirectional transistors, stored charge, different signal strengths, and indeterminate (X) logic values. The LGCC program translates the Boolean representation into a set, of machine language evaluation procedures and initialized data structures.These procedures and data structures are compiled along with code implementing the simulation kernel and user interface fo produce the simulation program.The simulation program runs an order of magnitude faster than our previous simulator MOSSIM II. 24th ACM/IEEE Design Automation Conference Paper 2.2 0 I 987 ACM 0738-IOOX/87/0600-0009$00.75 9
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