Incremental Methods for FSM Traversal
15 Pages Posted: 17 Nov 2020
Date Written: 1995
Computing the set of reachable states of a finite state machine, is an important component of many problems in the synthesis, and formal verification of digital systems. Computing the reachable states is computationally expensive due to the "explosion" in the number of states in real designs. However, the process of design is usually iterative, and the designer may modify and recompute information many times. Unfortunately, the reachability computation is called each time the designer modifies the system, because current methods for reachability analysis are not incremental.
The representation of the reachable states that is currently used  in synthesis and verification, is inherently non-updatable; in addition it tends to have a large representation, even when the
finite state machine itself has a compact representation. We solve all these problems by presenting alternate ways to represent the reachable set, and incremental algorithms that can update the new representation each time the designer changes the system. The incremental algorithms use the reachable set computed at a previous iteration, and information about the changes to the system to update it, rather than compute the reachable set from the beginning. This results in considerable savings in time, as demonstrated by the results
Keywords: incremental algorithms, iterative design, computer aided design, finite state machine traversal, state space exploration
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