πDD: a new decision diagram for efficient problem solving in permutation space

  • Authors:
  • Shin-ichi Minato

  • Affiliations:
  • Hokkaido University, Sapporo, Japan

  • Venue:
  • SAT'11 Proceedings of the 14th international conference on Theory and application of satisfiability testing
  • Year:
  • 2011

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Abstract

Permutations and combinations are two basic concepts in elementary combinatorics. Permutations appear in various problems such as sorting, ordering, matching, coding and many other real-life situations. While conventional SAT problems are discussed in combinatorial space, "permutatorial" SAT and CSPs also constitute an interesting and practical research topic. In this paper, we propose a new type of decision diagram named "pDD," for compact and canonical representation of a set of permutations. Similarly to an ordinary BDD or ZDD, pDD has efficient algebraic set operations such as union, intersection, etc. In addition, pDDs hava a special Cartesian product operation which generates all possible composite permutations for two given sets of permutations. This is a beautiful and powerful property of pDDs. We present two examples of pDD applications, namely, designing permutation networks and analysis of Rubik's Cube. The experimental results show that a pDD-based method can explore billions of permutations within feasible time and space limits by using simple algebraic operations.