Enriching Non-Parametric Bidirectional Search Algorithms

  • Shahaf S. Shperberg Ben-Gurion University
  • Ariel Felner Ben-Gurion University
  • Nathan R. Sturtevant University of Alberta
  • Solomon E. Shimony Ben-Gurion University
  • Avi Hayoun Ben-Gurion University


NBS is a non-parametric bidirectional search algorithm proven to expand at most twice the number of node expansions required to verify the optimality of a solution. We introduce new variants of NBS that are aimed at finding all optimal solutions. We then introduce an algorithmic framework that includes NBS as a special case. Finally, we introduce DVCBS, a new algorithm in this framework that aims to further reduce the number of expansions. Unlike NBS, DVCBS does not have any worst-case bound guarantees, but in practice it outperforms NBS in verifying the optimality of solutions.

AAAI Technical Track: Heuristic Search and Optimization