Author: Vasik Rajlich
Date: 08:57:33 05/27/04
Go up one level in this thread
On May 27, 2004 at 11:22:40, Vincent Diepeveen 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. > >that sounds very high. Ok - just checked - it's more like 93-94%, and I'm doing MTD (f). > >>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. I meant an IID where the move that already failed low is thrown out. You want the second-best move at the reduced depth. Usually, you will waste a few nodes this way of course. The idea is to avoid-the worst case scenario - of doing a full search through a bunch of other moves, before finding the fail-high move. > >>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. Well that's the million dollar question, isn't it? Vas
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.