Author: Gerd Isenberg
Date: 09:57:47 05/22/03
Go up one level in this thread
On May 22, 2003 at 11:42:45, Ulrich Tuerke wrote: >On May 22, 2003 at 11:16:18, David H. McClain wrote: > >>On May 22, 2003 at 08:41:56, Ulrich Tuerke wrote: >> >>>On May 22, 2003 at 06:08:47, José Carlos wrote: >>> >>>>On May 22, 2003 at 01:01:38, Robin Smith wrote: >>>> >>>>>Often programs will underpromote a pawn in situations where they think capturing >>>>>the (under)promoted piece is still the best reply. Can anyone give an example >>>>>from an actual game where this underspromotion cost the computer a 1/2 point? >>>>> >>>>>Robin >>>> >>>> I can't recall any game with this problem, but it's really easy to fix. I >>>>simply order the promotions so that promoting to queen gets searched first. >>> >>>Isn't everybody doing this anyway ? >>>Uli >>> >>>> The >>>>all the other underpromotions will return alpha and thus ignored. >>>> >>>> José C. >> >>Jose, >> >>No, everyone is not doing this. At least I am not. Admittedly I have played >>only one game where an underpromotion was an absolute necessity to regain tempo >>and obtain a "check" to prevent a checkmate to the other side. This was to a >>knight promotion rather than a Queen. And the game was eventually won with the >>knight promotion. I'm sure others have witnessed this on occasion also. >> >>Don't ask me to find and post this game. I don't know where or if I have it but >>I simply regarded it as "the program knows best" and let it go at that. The >>program was correct.......... > >I don't think that we are talking about omitting under-promotions but about >move-ordering solely. > >When generating moves in full search, I sort promotions like > >1. queen >2. knight >3. rook >4. bishop > >That's because rook or bishop promotions will only very rarely generate a cut in >a case where the queen doesn't. Usually, the queen will do anyway. > >However, the knight may be a serious alternative to a queen promotion. >Therefore, I prefer it to rook and bishop. > >This way, you can't miss a win by knight promotion. > >In quies search, I omit (3) and (4). > >Uli Hi Uli, i do some kind of conditional delayed minor promotion move generation. Depending on the outcome of the queen promotion, assuming the queen promotion don't cuts, i omit all minor promotions or at least rook and bishop promotions. If the best reply of the opponent after doing the queen promotion is a capture of this queen, i see no need to even generate any minor promotion, except at the root and except knight promotion checks (maybe a rare double check). I also omit rook and bishop promotions, if the queen promotion returns no draw (stalemate) score. Gerd
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