A Repeated-Update Problem in the DeltaBlue Algorithm

  • Authors:

  • Tetsuya Suzuki;Takehiro Tokuda

  • Affiliations:

  • Department of Computer Science, Tokyo Institute of Technology, Ohokayama, Meguro, Tokyo 152-8552, Japan;Department of Computer Science, Tokyo Institute of Technology, Ohokayama, Meguro, Tokyo 152-8552, Japan

  • Venue:
  • Constraints
  • Year:
  • 1998

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Abstract

We observea repeated-update problem in the process of updating walkaboutstrengths of the DeltaBlue algorithm, which is known as a fastconstraint solving method based on local propagation. Accordingto the basic references on the DeltaBlue algorithm, the timecomplexity of the planning phase is described as O(MN)for a constraint problem such that the number of constraintsis N and the maximum number of methods a constrainthas is M. We, however, point out that the time complexityis not O(MN) using a very simple example. In thisexample, the time complexity is exponential order for N.Then we present a corrected DeltaBlue algorithm whose time complexityis O(EN^2) for a constraint problem such that thenumber of constraints is N and the maximum numberof variables a constraint has is E. Finally we measurethe performance of the corrected DeltaBlue algorithm using twobenchmarks.