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History Tables

The "history heuristic" is a descendant of the "killer move" technique.  A thorough explanation belongs in the article on search; for now, it will be sufficient to say that a history table should be maintained to note which moves have had interesting results in the past (i.e., which ones have cut-off search quickly along a continuation) and should therefore be tried again at a later time.  The history table is a simple 64x64 array of integer counters; when the search algorithm decides that a certain move has proven useful, it will ask the history table to increase its value.  The values stored in the table will then be used to sort moves and make sure that more "historically powerful" ones will be tried first.

Next : Pre-processing move generation