Changes

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.

An EGTB is a set of endgames. Each endgame is a set of records about positions’ information. All involving positions of that in an endgame that must have similar the same material. Each position has 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  Based on values those integer numbers can answer directly two questions of the EGTB: for a given position it is a draw or a win/loss position and how far it is from mating/being mated or converting. From those numbers , the best move of an endgame are simply organized a position can be indirectly calculated as an array below part mentions. Theoretically, we can add more information to each position’s record. However, due to large numbers of integersinvolving positions, any additional information may make the whole EGTB becomes significantly larger. In other words, Thus so far none of popular EGTBs store any extra information for each item in and each record actually contains that array is an integer and mapped to a unique positiononly.

The array All records of an endgame can be stored are simply organized as two arrays (one array for one side/color). In other words, each item in one or those arrays is an integer and its index on an array is mapped to a unique position. For a few filesgiven chess position, in none or compressed formatswe will calculate its index then access its data record/integer via that index without searching.

* The number of involving pieces: more pieces , the bigger size

* The largest value: the integer number: should be large enough to cover the largest value. Different endgames will have different largest values. Thus some endgames need only one byte to store a number of a position per item but some need 2 bytes

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. 

* [[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