Author: Tord Romstad
Date: 04:12:08 08/12/04
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On August 12, 2004 at 06:40:48, Ross Boyd wrote: >Be careful with R=3. It has the potential to make your engine go blind. I lost >~50 (!!) elo when using pure R=3 in TRACE. I ran the experiment again two days >ago and it confirmed my previous findings. Currently, pure R=2 works best for >me... fewer OTB blunders. Like virtually everything else in computer chess, this is something which varies a lot between different engines. In my engine pure R=3 works *much* better than R=2, and slighly bettter than the classic adaptive null move pruning technique. Verified null move pruning also didn't work for me. The only improvement I have found over pure R=3 is a scheme were I occasionally use R=2 in positions where horizon effect problems are likely to be a problem (I use the eval to make the decision). Part of the reason that R=3 is best for me could be that my engine doesn't use null moves as much as most other engines. I only do a null move search when I am reasonably sure of a fail-high, but not quite sure enough to prune the whole subtree without search. Null move at all nodes more than doubles my node count, and does not increase the accuracy of my search noticably. Tord
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