Difference between revisions of "Hash Move"

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The '''Hash Move''' is a move probed from the [[Transposition Table|transposition table]], either a [[Best Move|best move]] of a stored [[Node Types#PV|PV-node]] - a [[PV-Move|PV-move]], or a good enough [[Refutation Move|refutation move]] to cause a [[Beta-Cutoff|cutoff]]. This move should most importantly searched first <ref>but usually after trying the [[Null Move]] of the [[Null Move Pruning|Null Move Heuristic]]</ref> <ref> [http://www.talkchess.com/forum/viewtopic.php?t=64093 tt move vs null move] by [[Erin Dame]], [[CCC]], May 27, 2017</ref>. One may save the [[Move Generation|move generation]] at all, if the hash move actually [[Fail-High|fails high]]. To guard against rare  [[Transposition Table#KeyCollisions|TT key collisions]], one may apply a [[Legal Move|legality test]] of the hash move <ref>[[Robert Hyatt]], [[Anthony Cozzie]] ('''2005'''). ''[http://www.cis.uab.edu/hyatt/collisions.html The Effect of Hash Signature Collisions in a Chess Program]''. [[ICGA Journal|ICGA Journal, Vol. 28., No. 3]]</ref>.
 
The '''Hash Move''' is a move probed from the [[Transposition Table|transposition table]], either a [[Best Move|best move]] of a stored [[Node Types#PV|PV-node]] - a [[PV-Move|PV-move]], or a good enough [[Refutation Move|refutation move]] to cause a [[Beta-Cutoff|cutoff]]. This move should most importantly searched first <ref>but usually after trying the [[Null Move]] of the [[Null Move Pruning|Null Move Heuristic]]</ref> <ref> [http://www.talkchess.com/forum/viewtopic.php?t=64093 tt move vs null move] by [[Erin Dame]], [[CCC]], May 27, 2017</ref>. One may save the [[Move Generation|move generation]] at all, if the hash move actually [[Fail-High|fails high]]. To guard against rare  [[Transposition Table#KeyCollisions|TT key collisions]], one may apply a [[Legal Move|legality test]] of the hash move <ref>[[Robert Hyatt]], [[Anthony Cozzie]] ('''2005'''). ''[http://www.cis.uab.edu/hyatt/collisions.html The Effect of Hash Signature Collisions in a Chess Program]''. [[ICGA Journal|ICGA Journal, Vol. 28., No. 3]]</ref>.
 
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=See also=
 
=See also=
 
* [[Best Move]]
 
* [[Best Move]]
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* [http://www.talkchess.com/forum/viewtopic.php?t=64093 tt move vs null move] by [[Erin Dame]], [[CCC]], May 27, 2017 » [[Null Move]], [[Null Move Pruning]]
 
* [http://www.talkchess.com/forum/viewtopic.php?t=64093 tt move vs null move] by [[Erin Dame]], [[CCC]], May 27, 2017 » [[Null Move]], [[Null Move Pruning]]
 
* [http://www.talkchess.com/forum/viewtopic.php?t=65189 Marginal hash move] by [[Harm Geert Muller]], [[CCC]], September 16, 2017
 
* [http://www.talkchess.com/forum/viewtopic.php?t=65189 Marginal hash move] by [[Harm Geert Muller]], [[CCC]], September 16, 2017
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* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=76887 Hash move ordering vs. Hash cuts: savings in number of nodes visited] by [[Marcel Vanthoor]], [[CCC]], March 16, 2021
 
* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=76888 Best move from previous iteration first: still needed with TT?] by [[Marcel Vanthoor]], [[CCC]], March 16, 2021 » [[PV-Move]]
 
* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=76888 Best move from previous iteration first: still needed with TT?] by [[Marcel Vanthoor]], [[CCC]], March 16, 2021 » [[PV-Move]]
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* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=77593 PV-move ordering necessary if you have TT-move ordering?] by [[Marcel Vanthoor]], [[CCC]], July 01, 2021
  
 
=References=
 
=References=

Latest revision as of 08:17, 4 July 2021

Home * Chess * Moves * Hash Move

The Hash Move is a Move Ordering related issue.

The Hash Move is a move probed from the transposition table, either a best move of a stored PV-node - a PV-move, or a good enough refutation move to cause a cutoff. This move should most importantly searched first [1] [2]. One may save the move generation at all, if the hash move actually fails high. To guard against rare TT key collisions, one may apply a legality test of the hash move [3].

See also

Collisions

Forum Posts

References

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