A Solution to the GHI Problem for Best-First Search

DM Breuker*, HJ van den Herik, JWHM Uiterwijk, LV Allis

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterAcademic


In a search graph a node's value may be dependent on the path leading to it. Different paths may lead to different values. Hence, it is difficult to determine the value of any node unambiguously. The problem is known as the graph-history-interaction (GHI) problem. This paper provides a solution for best-first search. First, we give a precise formulation of the problem. Then, for best-first search and for other searches, we review earlier proposals to overcome the problem. Next, our solution is given in detail. Here we introduce the notion of twin nodes, enabling a distinction of nodes according to their history. The implementation, called BTA (Base-Twin Algorithm), is performed for pn search, a best-first search algorithm. It is generally applicable to other best-first search algorithms. Experimental results in the field of computer chess confirm the claim that the GHI problem has been solved for best-first search.
Original languageEnglish
Title of host publicationComputers and Games
Publication statusPublished - 1999

Publication series

SeriesLecture Notes in Computer Science


  • graph-history interaction (GHI) problem
  • best-first search
  • base-twin algorithm (BTA)


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