Planning with abstraction hierarchies can be exponentially less efficient

  • Authors:

  • Christer Backstrom;Peter Jonsson

  • Affiliations:

  • Department of Computer and Information Science, Linkoping University, Linkoping, Sweden;Department of Computer and Information Science, Linkoping University, Linkoping, Sweden

  • Venue:
  • IJCAI'95 Proceedings of the 14th international joint conference on Artificial intelligence - Volume 2
  • Year:
  • 1995

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Abstract

It is well-known that state abstraction can speed up planning exponentially, under ideal condi tions. We add to the knowledge--showing that state abstraction may likewise slow down planning exponentially, and even result in generat ing an exponentially longer solution than necessary. This phenomenon can occur for abstraction hierarchies which are generated automatically by the ALPINE and HIGHPOINT algorithms. We further show that there is little hope of any drastic improvement upon these algorithms--it is computationally difficult to generate abstraction hierarchies which allow finding good approximations of optimal plans.