Formal Models of Heavy-Tailed Behavior in Combinatorial Search

  • Hubie Chen
  • Carla Gomes
  • Bart Selman
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2239)


Recently, it has been found that the cost distributions of randomized backtrack search in combinatorial domains are often heavytailed. Such heavy-tailed distributions explain the high variability observed when using backtrack-style procedures. A good understanding of this phenomenon can lead to better search techniques. For example, restart strategies provide a good mechanism for eliminating the heavytailed behavior and boosting the overall search performance. Several state-of-the-art SAT solvers now incorporate such restart mechanisms. The study of heavy-tailed phenomena in combinatorial search has so far been been largely based on empirical data. We introduce several abstract tree search models, and show formally how heavy-tailed cost distribution can arise in backtrack search. We also discuss how these insights may facilitate the development of better combinatorial search methods.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • Hubie Chen
    • 1
  • Carla Gomes
    • 1
  • Bart Selman
    • 1
  1. 1.Department of Computer ScienceCornell UniversityIthacaUSA

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