Changes

When a [[Chess Game|chess game]] goes to the [[Endgame|endgame]] phase, it may complete soon with the result as a draw or a win/loss. Both human/chess engines can finish the endgame by continuing searching, applying some endgame rules. The Even the game can finish in this way but it is not in a perfect way: it takes much time to make movecompute moves, may use more moves than necessary. Sometimes the winning side may lose the change since the rule 50 movesand/or making blunders. Both human and chess engines may miss badly the chances if they don’t know or not good enough about the endgame they are playing.

An EGTB can help to solve this period. It is a kind of a dictionary of all endgame positions which can answer directly or indirectly immediately for a given position:* If it is a draw or a win/loss* how How far/how many move from matting/being mated* what What is the best move

* It does not Engines don’t have to search but retrieves data thus it they can move instantly* The move is Moves are the perfect oneones, leading the shortest line to win* Engines don’t need to have the knowledge and code about those endgames

* Data Their data typically are too large for downloading and storing* If use when searching, it They may slow down the search* Require a complicated code codes for probing

An EGTB is a set of endgames. Each endgame is a set of records about positions’ information. All involving positions (they in an endgame must have the same material). Each Typically each position 's record associates with an integer number which informs how far that position is from mating/being mated or converting (depends on the type of its metrics). All numbers of an endgame are simply organized as two arrays of integers (one array for one side/color). In other words, each item in those arrays is an integer and its index on an array is mapped to a unique position.

Those arrays Based on values of an endgame those integer numbers it can be stored in files. Popularly each array answer directly two questions of the EGTB: 1) for a given position it is a draw or a win/loss position and 2) how far it is stored in one filefrom mating/being mated or converting. But sometimes they To answer the 3rd question, the best move of a position can be combined into one file. Those files may be in the form of none or compressed. If they are compressedindirectly calculated: generate all legal moves, make them, they are divided and compressed by small blocks thus they don't need to decompress probe all to extract data of few new positions, compare probing scores for the highest one and the associated move is the best one.

When a chess program (e.g., a chess engine or a chess GUI) works with an EGTB, it needs to retrieve data (integer numbers) for some given chess positions. The process named probe. It is not a search but retrieve data which and has below steps:

* access data (typically organized organised as an integer arrayarrays of integers) using the index to retrieve the integer of that chess position

* From data index calculate to the block index

* Uncompress the block data (if it is compressed)* Convert the endgame index into block index and retrieve the right needed data

Typically the probe process requires some computing and it may access storage and decompress which is usually so slow, compared with one stored in memory. All may make it be a slow one. An engine that probes EGTB when searching may make the whole search be slower. Sometimes the benefit from probing EGTBs maybe not enough to cover the loss of slower search. That’s why the probing should be planned and implemented carefully. EGTB files may have to store in fast storage and/or using some huge systems’ caches. The good point is that the engine can stop searching on the branch probed the EGTB. 

* [[Christoph Wirth]], [[Jürg Nievergelt]] ('''1999'''). ''Exhaustive and Heuristic Retrograde Analysis of the KPPKP Endgame.'' [[ICGA Journal#22_2|ICCA Journal, Vol. 22, No. 2]]<ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?f=6&t=2923 Chris Wirth's endgame tablebases] by [[Denis Mendoza|Denis P. Mendoza]], [[Computer Chess Forums|CCRL Endgame Tablebases]], December 13, 2007 » [[Chessterfield]]</ref>

* [[Ulrich Thiemonds]] ('''1999'''). ''Ein regelbasiertes Spielprogramm für Schachendspiele''. [https://en.wikipedia.org/wiki/University_of_Bonn University of Bonn], Diploma Diplom thesis, [httphttps://www.iaiidb.uni-bonn.de/~idbpublications/diplomarbeitenda/thiemonds99.psda_thiemonds_1999.gz zipped pspdf pdf] (German)

* [https://www.chessdb.cn/queryc_en/ Chess Cloud Database Query Interface] by [[Bojun Guo|noobpwnftw]] [[Syzygy Bases|Syzygy]] DTZ50 probing