Author: John Scalo
Date: 16:55:51 09/28/98
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On September 28, 1998 at 16:48:57, John Coffey wrote: > >This code I understand, but ..... > >my question is about the following .... > >"A fail low is when you search a position and return a score <= alpha. A fail >high is when you return a score that is >= beta." > >What are the significance of "fail low" and "fail high" and how do they >affect the search? > >John Coffey The term "fail" is a little misleading I think because a "fail high" is usually a good thing - it means that branches of the search tree will (usually) be eliminated. In this sense your search succeeded, not failed :-) A fail low is going to have a different significance depending on your implementation. For example if you are using the PVS algorithm a fail low may mean that you have to re-search with a full alpha-beta window. In other implementations a fail low may rarely or never occur if you always start with alpha = -INF.
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