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Endgame Tablebases

3 bytes added, 12:37, 17 February 2021
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An EGTB is a set of endgames. Each endgame is a set of 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). Theoretically, we can add more information to each record. However, due to large involving positions, any additional information may make the whole EGTB becomes significantly larger. None of the popular EGTBs store any extra information for each item thus 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.
Based on values those integer numbers can answer directly two purposes 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 record. However, due to large involving positions, any additional information may make the whole EGTB becomes significantly larger. None of the popular EGTBs store any extra information for each item thus 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.
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 file or device into more files to be easy to copy or manage. Those files may be in the form of none or compressed. If they are compressed, they are divided and compressed by small blocks thus they don't need to decompress all to extract data of just a few positions.

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