Path-Dependency

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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, 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
 * 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=
 * Graph History Interaction (GHI)
 * Transposition
 * Transposition Table
 * Repetitions
 * Fifty-move Rule

=Forum Posts=

2000 ...

 * "Don't trust draw score" <=Is it true? by Teerapong Tovirat, CCC, August 08, 2001 » Repetitions, Graph History Interaction

2005 ...

 * path dependent evaluation by Daniel Shawul, Winboard Forum, April 20, 2005
 * Re: And a still unsolved test position by Uri Blass, CCC, June 09, 2005 » Movei
 * Semi-Path Dependent Hashing: a semi-useless idea by Zach Wegner, CCC, May 24, 2008 » Transposition Table

2010 ...

 * Repetitions/50 moves and TT by Sergei Markoff, CCC, September 13, 2011
 * Texel recipe to fix TT draws scores by Marco Costalba, CCC, June 23, 2012 » Texel

=External Links=
 * Path dependence from Wikipedia

=References=

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