Author: José Carlos
Date: 09:11:33 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 I recently implemented ignoring underpomotions in quies, because I read it in Ed's page (haven't figured it out myself before) and though about, as you do, try knight promotions (Ed doesn't). The problem is finding positions to test it. I think (haven't tested) that the need of underpromotions to knight in quies must be so rare in real life that Ed's approach should be better. Have you tested with and without? José C.
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