Author: Vincent Diepeveen
Date: 09:21:56 03/25/01
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On March 25, 2001 at 09:37:09, Robert Hyatt wrote: >On March 25, 2001 at 03:51:02, Pham Minh Tri wrote: > >>Hi, >>I am wondering why we do not search checking moves (moves check opponent king >>but do not capture) in qsearch function. I think they are not ?quiescence? and >>should be searched as capture moves. Does anyone try them? >>Thank very much for any explanation. >>Pham > > >I have two answers: > >1. I did q-search checks in Cray Blitz. I also did them in early versions >of crafty as you can see in the comments in main.c... > >2. I removed them a _long_ while back in Crafty. > >Here is my analysis: If you do q-search checks, you will find some tactical >lines significantly quicker, obviously. But since you are searching much >deeper along lines with lots of checks, overall you have to search less deeply >along non-checking lines, since you can only search a fixed number of nodes in >a fixed unit of time. >You have to make the following choice: either (a) find tactical shots that >depends on checks quicker, but give up some positional skills as positional As doing checks in qsearch finds tactics 4 ply sooner for me, sometimes even zillions of plies as i try unlimited number of checks in many cases in qsearch, for me it's quite easy to go for a here without ever considering b. Idem for many commercial programs. >moves will be searched less deeply; (b) find tactical shots slower, but then >search deeper in positional cases and find positional threats your opponent >won't be able to see because the checks prevent him from getting deep enough >to see it. > >I like the non-check approach because (1) I can search deeper overall, and in >non-tactical positions this pays off well; (2) the q-search code is much >simpler, which makes it even faster since so much of the total time is spent >there; > >Of course, everyone should try it themselves to make sure they get the same >results I get. I do know of several programs that use this approach with >great success. Note that I don't particularly think much of the idea of >searching checks very deeply but overlooking all of the _other_ kinds of >tactical moves you might include in the q-search. Pins. Attacking overloaded >pieces. etc... > >By keeping the q-search simple, the normal search handles more of the nodes, >and since that part of the search includes _everything_ you might be tactically >stronger by not overlooking something.
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