Author: Vasik Rajlich
Date: 08:55:44 05/27/04
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On May 27, 2004 at 06:46:50, Uri Blass wrote: >On May 27, 2004 at 06:39:23, Vasik Rajlich wrote: > >>On May 26, 2004 at 13:49:38, Tord Romstad wrote: >> >>>On May 26, 2004 at 13:34:23, Robert Hyatt wrote: >>> >>>>I have used "IID" for years, but in a very restricted way, namely to handle the >>>>case along the PV where I have no hash move. I've never tried it _everywhere_ >>>>before, so have no data. But I intend to try to see if it is something that >>>>could work, or if it is a waste... >>> >>>I am fairly sure you will find that _everywhere_ is a waste. It is probably >>>not worth doing near the leaf, you have a hash table move to search, or when >>>a fail-low is most likely. Perhaps you should also use a somewhat bigger >>>reduction factor than in your "along-the PV IID". >>> >>>Note that it could also be interesting to look for good ways to make use of the >>>return value of the internal search. It gives a reasonably reliable estimate >>>of the value of a full-depth search, and can be useful as an ingredient in >>>pruning tricks. The most obvious (and entirely risk-free) case is when the >>>reduced-depth search returns a mate score. When this happens, it is clearly >>>not necessary to do a full-depth search. >>> >>>Tord >> >>Yes, there is lots of room for playing with IID. >> >>Note that 95% of all nodes fail high in some way, so you can be pretty >>aggressive. > >The % of all nodes that fail high is dependent on the engine but it does not >seem to me logical that 95% of all nodes fail high in some way. > >After every nodes that fail high you may have many nodes that fail low because a >node that fail high means that all the node one ply after it must fail low. > >Uri Here are some sample fail high %s, from Rybka's last run: 93.5 93.6 92.9 93.4 93.0 94.4 My search has three layers, these are from the top layer. I think the #s would be slightly lower for a PVS search instead of MTD (f). As for the "logic" - don't forget that fail-low nodes will spawn more children than fail-high nodes. Vas
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