Unsynchronized iteratively deepening parallel alpha-beta search

A parallel alpha-beta search algorithm called unsynchronized iteratively deepening parallel alpha-beta search is described. The algorithm's simple control strategy and strong performance in complicated positions make it a viable alternative to the principal variation splitting algorithm (PVSA). Processors independently carry out iteratively deepening searches on separate subsets of moves. The iterative deepening is unsynchronized, e.g. one processor may be in the middle of the fifth iteration while another is in the middle of the sixth. Narrow windows diminish the importance of backing-up a score to the root of the tree as quickly as possible (one of the principal objectives of the PVSA). Speedups measured on one, two, four, and eight chess-playing computers are reported.<
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