====== Chess - Programming - Hash Functions ======

Hash functions convert chess positions into an almost unique, scalar signature, allowing fast index calculation as well as space saving verification of stored positions.

Common Hash Functions are:

  * [[Chess:Programming:Zobrist Hashing|Zobrist Hashing]]
  * [[Chess:Programming:BCH Hashing|BCH Hashing]]

<WRAP info>
**NOTE:**  They use fast hash functions, to provide hash keys or signatures as a kind of Gödel number of chess positions, today typically 64-bit wide. 

  * They are updated incrementally during make and unmake move by either own-inverse exclusive or or by addition versus subtraction.

</WRAP>

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===== References =====

https://www.ics.uci.edu/~eppstein/180a/970424.html