Author: Gian-Carlo Pascutto
Date: 12:06:58 09/18/00
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On September 18, 2000 at 13:50:51, Uri Blass wrote: >I believe that big part of the results without dynamic null move pruning are >different. >The main problem is not zunzwangs but cases when the null move pruning prune >line that has a deep threat. I don't think this is true at ply depths this large. Even with the most aggressive pruning the lines still only go from 16->11 ply. If a threat doesn't show up in those eleven plies it is nearly sure it can be avoided with an extra move. These arent exactly zugzwang situations either, but very active ones. The more active, the less the chance for a nullmove error.(sortof) In short, I think aggressive dynamic nullmove pruning is accetable at these depths in these positions. If I thought it weren't, I wouldn't have used it. >I also believe that extensions are important and 15 plies with the normal >extensions may be better for analysis than 16 plies when you tune down >extensions and razoring. This is true. But reaching 15 ply with the standard search is damn HARD. I didn't tune down razoring btw but re-added it. Bob got rid of it in 16.18 because the gain of 20-30% wasn't significant enough related to the risk. Again, at ply depths this large things are different. >If you want good analysis of the position the best thing to do is to ask the >top programs to use a long time and not to goto big depth. Probably true. However Dan is right about the fact that extensions are gambling. Sometimes they see it, sometimes they don't. Using a large standard search always sees it, save the nullmove/razoring failures, which are really small. As a related note, my modified crafty gets a big fail-high on the Nf6 at ply 8 whereas standard crafty only gets it at ply 9. Search is a weird beast. -- GCP
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