Changes

An EGTB is a set of endgames. Each endgame is a set of records about positions’ information record. All involving positions in an endgame must have the same material. Each position 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).

Based on values those integer numbers can answer directly two purposes 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 a position can be indirectly calculated as below part mentions.

Theoretically, we can add more information to each position’s record. However, due to large numbers of involving positions, any additional information may make the whole EGTB becomes significantly larger. None Thus so far none of the popular EGTBs store any extra information for each item thus and each record actually contains that integer only.

All records of an endgame are simply organized as two arrays (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. For a given chess position, we will calculate its index then access its data record/integer via that index without searching.

==Endgame files==Those arrays of an endgame can be stored in files. Typically each array is stored in one file. However, sometimes they can be combined into one larger file or device splitted into more files to be easy to easier copy or manage. Those files may be in the form of none or compressed. If they are compressed, they are typically divided and compressed by small blocks thus they don't need to load and decompress all data to extract data of just a few positionsposition.

* 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. 

* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=76089 Asynchronous tablebase lookups] by [[Steinar H. Gunderson|Sesse]], [[CCC]], December 17, 2020 <ref>[https://kernel.dk/io_uring.pdf?source=techstories.org io_uring.pdf]</ref>'''2021'''* [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=76089 Asynchronous tablebase lookups76659 Stalemate Tablebases] by [[Steinar H. Gunderson|Sesse]]Dries De Clercq, [[CCC]], December 17February 21, 2020 <ref>2021 » [[https://kernel.dk/io_uring.pdf?source=techstories.org io_uring.pdfStalemate]]</ref>