Author: Robert Hyatt
Date: 06:37:09 03/25/01
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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 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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