Mixing Forward and Backward Traversals in Guided-Prioritized BDD-Based Verification

Abstract

Over the last decade BDD-based symbolic manipulations have been among the most widely used core technologies in the verification domain. To improve their efficiency within the framework of Unbounded Model Checking, we follow some of the most successful trends proposed in this field. We present a very promising approach based on: Mixing forward and backward traversals, dovetailing approximate and exact methods, adopting guided and partitioned searches, efficiently using conjunctive decompositions and generalized cofactor based BDD simplifications. One of the main contributions of this paper is a backward verification procedure based on a prioritized traversal. We call the method "inboundpath-search". Initially, an approximate forward traversal produces overapproximate onion-ring frontier sets. After that, these rings are used as distance estimators and guides to partition state sets in terms of the estimated distance from the "target" set of states. Finally, while the subsequent search is performed, the higher priority is given to the subset with the smallest estimated distance. We experimentally compare our methodology with a state-of-the-art technique (approximate-reachability don't cares model checking) implemented in the freely available VIS tool. Results show interesting improvements in terms of both efficiency and power.

Intertwined Forward-Backward Reachability Analysis Using Interpolants

“…For simplicity of the presentation, we use iterative local strengthening both forward and backward instead of using an interpolation-sequence for the backward update. 3 An EDA company: http://www.jasper-da.com Table 1. Parameters of the experiments.…”

“…Traditionally, BDD-based verification methods [6] use both forward and backward analyses [3,13], while SAT-based methods mainly implement the forward one. Recently, a few works considered backward analysis in the context of SAT as well (e.g.…”

Benchmarking a model checker for algorithmic improvements and tuning for performance

“…-BDD-based representations and traversals, including forward, backward, combined (approximate)forward/(exact)backward algorithms [26,27], partitioned BDDs and/or image computation procedures [28,29]. -Interpolant-based verification, with ad-hoc abstraction and tightening techniques [18,19], integrated SAT-based approaches [20,21].…”

Interleaved Invariant Checking with Dynamic Abstraction

“…The second body of work that this paper draws upon, is the combination of forward and backward state space traversals to perform symbolic invariant checking. Several works such as [3,4,10,12] use a combination of forward and backward traversal whereby one sweep of traversal is used to approximate or prune the search space and subsequently the other sweep is used to perform the actual verification. This process may potentially be iterated.…”