Author: Scott Gasch
Date: 11:59:48 08/03/99
Recently I have been trying to limit the number of qeval positions my program deals with in order to have it spend its time more wisely looking at relevant positions. In a previous thread Bob Hyatt had a really good suggestion about how to limit seemingly irrelivant positions -- to recap, if score is way below alpha in the qeval routine and the value of a capture does + your greatest possible positional bonus does not bring it over alpha, no sense in considering the position caused by this capture. I am also limiting hte max depth of the qeval search to depth + 12 ply (6 captures on each side). This causes moderate improvement in very "busy" positions. I chose 12 because it is even (each side gets to capture the same number of times) and I have rarely seen a chess game where the best course of action is a string of 6 captures per side in a row. However, I am returning the static "eval" of the position at this depth and I am worried that this may lead to inaccuracy...? But I can't think of another score to assign this depth qnode. I am still seeing poor performance, in qeval. In a typical "busy" middlegame I am seeing about 4 million qeval calls with about 2 million "cuts" due to the alpha rule (above) and about 200,000 cuts due to max depth exceeded. In these types of positions it takes about 45 sec just to finish searching at 4 ply depth! Does anyone have comments on these techniques for pruning qeval paths and/or have any better ideas? Scott
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