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Path-Dependency describes a situation when the same position gets a different value depending on a sequence of moves by which it has been reached. Whilst a few programs do this by design [1], within the standard alpha-beta framework path-dependency is considered undesirable, if impossible to avoid.

Typical Cases

  • The position can be treated differently if there is a chance of repetition or hitting into a fifty-move rule.
  • Different move ordering can cause different result (different moves causing a cutoff), when it comes from the hash table [2]
  • Hf a program uses search extensions, search depth may be different (i.e. 1. d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Nf3 vs 1.d4 Nf6 2.c4 e6 3.Nf3 Bb4+ 4.Nc3, where only the latter triggers a check extension)
  • History-dependent heuristics, like some versions of LMR may prune different sub-trees.

See also

Forum Posts

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External Links


  1. Re: Methods to stably evaluate nodes? by Uri Blass, CCC, May 05, 2007
  2. Tony Warnock, Burton Wendroff (1988). Search Tables in Computer Chess. ICCA Journal, Vol. 11, No. 1, pp. 10-13.

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