An Analysis of Bitstate Hashing

  • Authors:
  • Gerard J. Holzmann

  • Affiliations:
  • Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974, USA

  • Venue:
  • Formal Methods in System Design
  • Year:
  • 1998

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Abstract

The bitstate hashing, or supertrace, technique wasintroduced in 1987 as a method to increase the qualityof verification by reachability analyses for applicationsthat defeat analysis by traditional means because of their size.Since then, the technique has been included in many researchverification tools, and was adopted in tools thatare marketed commercially.It is therefore important that we understand well how andwhy the method works, what its limitations are, and how itcompares with alternative methods over a broad range ofproblem sizes.The original motivation for the bitstate hashing techniquewas based on empirical evidence of its effectiveness.In this paper we provide an analytical argument.We compare the technique with two alternatives thathave been proposed in the recent literature.We also describe a sequential bitstate hashing techniquethat can be of value when confronted with very largeproblem sizes.