chess:programming:zobrist_hashing
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| chess:programming:zobrist_hashing [2021/10/30 21:27] – peter | chess:programming:zobrist_hashing [2021/10/30 21:41] (current) – [Implementation Consideration] peter | ||
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| ====== Chess - Programming - Zobrist Hashing ====== | ====== Chess - Programming - Zobrist Hashing ====== | ||
| - | **Zobrist Hashing** is a technique to transform a board position of arbitrary size into a number of a set length, with an equal distribution over all possible numbers. | + | **Zobrist Hashing** is a hashing function that is widely used in 2 player |
| * The main purpose of Zobrist hash codes in chess programming is to get an almost unique index number for any chess position, with a very important requirement that two similar positions generate entirely different indices. | * The main purpose of Zobrist hash codes in chess programming is to get an almost unique index number for any chess position, with a very important requirement that two similar positions generate entirely different indices. | ||
| - | * These index numbers are used for faster and more space efficient Hash tables or databases, e.g. transposition tables and opening books. | + | |
| + | * Transposition tables basically store the evaluated values of previous board states, so that if they are encountered again we simply retrieve the stored value from the transposition table. | ||
| + | | ||
| ---- | ---- | ||
| [[Chess: | [[Chess: | ||
| - | |||
| - | ---- | ||
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| - | Zobrist Hashing is a hashing function that is widely used in 2 player board games. | ||
| - | |||
| - | * It is the most common hashing function used in transposition tables. | ||
| - | * Transposition tables basically store the evaluated values of previous board states, so that if they are encountered again we simply retrieve the stored value from the transposition table. | ||
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| <code cpp> | <code cpp> | ||
| - | piece*color*square * 8 + 3*8) bits; | + | (piece*color*square * 8 + 3*8) bits; |
| </ | </ | ||
| * This will reduce array of about 8th in size. | * This will reduce array of about 8th in size. | ||
| - | If a bit boundary is used, the array becomes | + | If a bit boundary is used, the array becomes: |
| <code cpp> | <code cpp> | ||
| - | piece*color*square + 63) bits; | + | (piece*color*square + 63) bits; |
| </ | </ | ||
chess/programming/zobrist_hashing.1635629233.txt.gz · Last modified: 2021/10/30 21:27 by peter