Author: Vincent Diepeveen
Date: 08:22:40 05/27/04
Go up one level in this thread
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. that sounds very high. >The IID principle can also apply to some additional situations: >1) You have a hash move, but it's at depth-2 rather than depth-1. You can do >another IID layer in this case. In that case hashmoves works better of course. >2) Your fail-high hash move (for some engines the only possible kind of hash >move) fails low. Here you can do IID to get an alternative move. This is highly unlikely as your IID is at depth-i where i > 0. So most likely that hashmove is already from a position j >= depth - i, which makes IID a complete waste of your time. >And - as Tord mentioned - an IID search can be turned into the final >reduced-depth search, based on its result. >Vas Depth reducing the current search? Sounds like a rather bad idea to me.
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