Author: Reinhold Gellner
Date: 23:43:12 10/22/97
Doing a zero-window search, fail high moves have to be re-searched. Usually I do it with actual_value = -re_search( -beta, -actual_value ); However, as extensions or just move ordering changes, the re_search is not neccessarily the same and may result in a fail low! That is, actual_value is now below the former actual_value but >= alpha. I think this is a common problem. I have three solutions: 1. ignore this fail low at all 2. do another re_search: actual_value = -re_search( -actual_value, -alpha) 3. do the initial re_search an open window: actual_value = - re_search( -beta, -alpha ); ad 1) this version may be dangerous in blitz games and of no importance in tournament games, resulting in a speed up. ad 2) the second search may now fail high again, or even oscillate, resulting in an eternal loop. ad 3) this safe approach seems to significantly increase the effective branching factor. How do you solve this problem? Reinhold
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