585
edits
Changes
no edit summary
'''Endgame Tablebases''', (EGTBs or EGTs)<br/>
precalculated [[Endgame|endgame]] [https://en.wikipedia.org/wiki/Table_%28database%29 tables] generated by an exhaustive [[Retrograde Analysis|retrograde analysis]]. During its [[Chess Game|game play]] and/or [[Search|search]], [[Interior Node Recognizer|recognizing]] a specific [[Material|material composition]], a chess program can probe, or in principle compute these tables to determine the outcome of positions definitively and act as an [[Oracle|oracle]] providing the optimal moves. The tables are usually divided into separate [https://en.wikipedia.org/wiki/Computer_file files] for each material configuration and [[Side to move|side to move]]. What all different [[Endgame Tablebases#Formats|formats]] of tablebases have in common is that every possible piece placement has its own, unique index number which represents the position where the information about the position is located in the file. Positions with non-null castling rights could be represented in an EGT EGTB but typically are not.
The term '''Tablebase''' opposed to endgame database was coined by [[Steven Edwards]] by means of a data vector and a single file access for both sides to move, when he introduced his [[Edwards' Tablebases]], addressing several shortcomings of [[Ken Thompson|Ken Thompson's]] earlier [[Thompson's Databases|database]] of positions with the weaker and hence potentially losing side to move only <ref>[[Ernst A. Heinz]] ('''1999'''). ''Endgame Databases and Efficient Index Schemes for Chess.'' [[ICGA Journal#22_1|ICCA Journal, Vol. 22, No. 1]], [http://people.csail.mit.edu/heinz/ps/edb_index.ps.gz ps]</ref> .
=Purpose=
When a playing game goes to the endgame period, it may complete soon by a draw or a win/loss. Both human/chess engines can finish the endgame by searching, applying some endgame rules. The game can finish in this way but it is not in a perfect way: it takes much time to make move, use more moves than necessary. Sometimes the winning side may lose the change since the rule 50 moves.
EGTB can help to solve this period. It is a kind of dictionary of all endgame positions which can answer directly or indirectly for a given position:
* it is a draw or a win/loss
* how far/how many move from matting/being mated
* what is the best move
The main advantages of using EGTBs:
* It does not search but retrieves data thus it can move instantly
* The move is the perfect one, leading the shortest line to win
The main disadvantages of using EGTBs:
* Data too large for downloading and storing
* Require complicated code for probing
=Data=
