zobrist hashing

Zobrist hashing is a technique used in computer science to efficiently hash multi-dimensional arrays or data structures. It was first introduced by Albert Zobrist in 1970 for use in board game programs.

The basic idea behind Zobrist hashing is to assign a unique hash value to each possible state of the data structure being hashed. This is done by generating a large number of random 64-bit integers (called "hash keys") and using them to represent the possible values of the data structure's elements.

To compute the hash value of a particular state of the data structure, the hash keys corresponding to the elements of the structure are XORed together. This results in a single 64-bit integer that serves as a unique identifier for the state.

The advantage of Zobrist hashing is that it allows for efficient comparison of two states of a data structure. Instead of comparing all the elements of the data structure one-by-one, the hash values can be compared, which is much faster.

Zobrist hashing is commonly used in algorithms for board games such as chess, where the state of the game can be represented as a multi-dimensional array. It is also used in other applications such as database indexing and data compression.