Author: Robert Hyatt
Date: 20:12:34 08/21/04
Go up one level in this thread
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...
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