Author: Scott Gasch
Date: 12:45:44 08/25/99
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This is one area of my chess program that I have trouble with too. First, we are doing this since scores of +/-mate are adjusted to reflect the ply at which they were found. Using these scores later when the ply can be totally different leads to inaccuracy. Let me see if I have the right idea about how to implement this: If you have converted ~ +/-mate scores into bounds, the lookup at the top of Search does not change at all... right? When storing a hash position, do it like this: If you have an EXACT score near +mate: convert to a LOWER_BOUND of mate - 200. This tells us later that this position is worth *at least* mate - 200. If you have an EXACT score near -mate: convert to an UPPER_BOUND of -mate + 200. This tells us later that this position is worth *at most* -mate + 200. If you have an UPPER_BOUND near mate do not hash it at all. Storing it is saying "this position is worth at most something very near +infinity" which is useless information. Even if you convert it to +mate - 200 it is still silly... "this position is worth at most +mate - 200... duh." Likewise if you have a LOWER_BOUND near -mate ignore it. "this position is worth at least something very near -infinity"... If you have a LOWER_BOUND near +mate convert it into a LOWER_BOUND of +mate - 200. If you have an UPPER_BOUND near -mate convert it into an UPPER_BOUND of -mate + 300. Thanks, Scott
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