Author: Robert Hyatt
Date: 20:53:02 08/23/04
Go up one level in this thread
On August 23, 2004 at 10:14:54, Stuart Cracraft wrote: >On August 21, 2004 at 23:12:34, Robert Hyatt wrote: > >>On August 21, 2004 at 19:24:01, Stuart Cracraft wrote: >> >>>On August 21, 2004 at 17:52:58, Robert Hyatt wrote: >>> >>>>On August 21, 2004 at 17:37:15, Stuart Cracraft wrote: >>>> >>>>>On August 21, 2004 at 17:23:30, Robert Hyatt wrote: >>>>> >>>>>>On August 21, 2004 at 13:20:11, Stuart Cracraft wrote: >>>>>> >>>>>>>All, >>>>>>> >>>>>>>SEE increases my nominal iteration depth by 0.42 pawns >>>>>>>given the same amount of time as a non-SEE search, all else >>>>>>> >>>>>>>SEE decreases my max quiescence depth reached (with a check handoff >>>>>>>to main search) by a little under 8 ply for the same problem set. >>>>>>> >>>>>>>These are the 300 positions from Win-at-Chess run at 1 second per >>>>>>>problem on an old, slow, notebook. I do not have comparative data >>>>>>>due to the subjectivity involved of chess games and the "feel of SEE". >>>>>>> >>>>>>>Legend: >>>>>>>Ave Iterative Depth/Average Max Search depth >>>>>>>% solved >>>>>>>Total solved / Total in test >>>>>>>Total time taken (300 seconds allowed) >>>>>>>Total Nodes searched >>>>>>>Average positions searched per problem / >>>>>>>Average time (rounded) per problem / >>>>>>>Average nodes per second per problem >>>>>>>0/0/Check Extensions from Quiescence back to Main Search/0/0 >>>>>>> >>>>>>>Without SEE >>>>>>> >>>>>>>**** 6.68/27.18 68% 204/300 269.05 54264704 180882/1/201692 0/0/3361112/0/0/0 >>>>>>> >>>>>>>With SEE >>>>>>> >>>>>>>**** 7.10/19.01 64% 193/300 267.44 46135172 153784/1/172505 0/0/1154026/0/0/0 >>>>>>> >>>>>>>Total problem solution rate drops 5.4% and nodes searched drops 14.98% >>>>>>> >>>>>>>(The SEE being used above was tried as (1) see < 0 then don't search >>>>>>>a capture move in quiescence and (2) see < delta where delta is calculated >>>>>>>with its margin off alpha as the maximum positional score so far in the >>>>>>>search for the side on move. The above results are the combination of both and >>>>>>>if only using the #2, assuming for example my SEE is not a great SEE, >>>>>>>the result is only slightly changed.) >>>>>>> >>>>>>>My question is, why should SEE reduce the tactical result so drastically >>>>>>>and is it safe to do so given the depth and nodes results are favorable? >>>>>>> >>>>>>>Thanks ahead, >>>>>>> >>>>>>>Stuart >>>>>> >>>>>> >>>>>>SEE should _help_ in tactics, not hurt. If it is hurting, there is something >>>>>>wrong somewhere... >>>>> >>>>>That's puzzling. I've tested it pretty thoroughly, manually, in a variety >>>>>of positions and think it is working right. It knows nothing of any secondary >>>>>effects, just the exchanging pieces. No x-rays, etc. >>>>> >>>>>Now I'm really nervous. >>>> >>>> >>>>No x-rays is a serious shortcoming. IE two rooks attacking the same square in >>>>battery. If you don't include the second rook I could see how SEE could cause >>>>problems. I handle X-rays pretty easily and always did even back in CB days... >>> >>>Yes -- X-rays have to be added. Finding them isn't a problem. It's what to >>>do with them after. I'll check around. >> >> >>That part is simple. Produce a list of pieces directly attacking the target. >>Each time you make a capture you _always_ use the smallest piece. And once you >>use it, if it is not a knight or king, you look "behind" the piece you just used >>to see if there is a piece that moves in the same direction. If so, add _that_ >>piece to the list of attackers, and the next cycle you still use the smallest >>piece from that list... >> >> >>Repeat until one side runs out of capturng pieces... >> >>Then minimax the result... > >Bob, I understand why one doesn't do it for the knight, but why not the king? >Example, a bishop and king on a diagonal. King captures pawn, some other >recapture, then the knight before the king recaptures the recapturer. > >I thik you have to look "behind" everything except the knight for x-ray >pieces, no? > >Stuart If the king captures on the target and is then captured, it doesn't matter whether there was a piece behind it or not. That capture was illegal.. :)
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