Author: James Robertson
Date: 02:15:26 08/20/99
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On August 20, 1999 at 05:01:55, Bruce Moreland wrote: > >On August 20, 1999 at 04:34:49, James Robertson wrote: > >>My program played a game in which this position arose: >> >>r3r1k1/3b1p1p/2p4q/p2p4/3P2p1/1PNPPpP1/P1RQ1P1P/5RK1 w - - >> >>It then played, after an 8 ply search, 1. e4?? which loses immediately to Qh3 >>and the loss of the queen after 1. e4?? Qh3 2. Qg5+ 3. Qf8 Qh6+ 4. Qxh6, an >>incredibly simple tactical sequence. I later ran my program on this position and >>it switched to the much much better move Kh1 after 6 plies. >> >>The only differece I can think of between the two searches would be the hash >>table? During the game it had entries from previous searches, and afterwards I >>ran it as a testsuite position with a clean table. I cannot fathom why else my >>program would miss such a thing in an actual game. Is there any reason why a >>hash table would do this? Is there some depth/draft thing I am messing up with >>my table? Is my null move causing problems? Any help anyone can provide is >>greatly appreciated. >> >>James >> >>P.S. Here are the two searches: >> >>a) during the game. >> >>Depth Score Time Nodes PV >> 1 216 0 35 Rfc1 >> 2 200 0 250 e4 Qxd2 Rxd2 >> 3 202 60 1263 Rfc1 Qh3 e4 >> 4 203 170 9783 e4 Qg7 Qe3 Rab8 >> 5 207 220 12885 e4 Qxd2 Rxd2 Be6 Rc1 >> 6 202 330 20163 e4 Qxd2 Rxd2 Be6 Rc1 Rab8 Rdc2 >> 7 199 550 40726 e4 Qxd2 Rxd2 Be6 Rc1 Rab8 Rdc2 Rb7 >> 8 199 1050 89464 e4 Qxd2 Rxd2 Be6 Rc1 Rab8 Nb1 Rb6 Nc3 >> >>b) after the game with a fresh hash: >> >>Depth Score Time Nodes PV >> 1 216 0 32 Rfc1 >> 2 200 0 255 e4 Qxd2 Rxd2 >> 3 202 270 1457 Rfc1 Qh3 e4 >> 4 203 380 10068 e4 Qg7 Qe3 Rab8 >> 5 199 440 14046 e4 Qxd2 Rxd2 Be6 Rc1 Rab8 >> 6> -160 660 38006 Ne2 fxe2 Qxe2 a4 Rb1 Qh3 e4 axb3 Rxb3 >> 6> -159 770 46432 b4 axb4 Nxd5 cxd5 Qxb4 Qh3 >> 6> 50 770 47608 h4 gxh3 Kh2 >> 6> 176 820 51711 Kh1 Qh3 Rg1 f5 Rcc1 Rab8 >> 6 176 820 51949 Kh1 Qh3 Rg1 f5 Rcc1 Rab8 >> 7 178 1100 76625 Kh1 Qh3 Rg1 f5 Rcc1 Rab8 Rge1 >> 8 184 2250 191340 Kh1 Qh3 Rg1 f5 Qd1 Rab8 Qf1 Qxf1 Rxf1 >> 9 184 5110 452120 Kh1 Qh3 Rg1 f5 Qd1 Rab8 Qf1 Qxf1 Rxf1 >> 10 176 9060 845582 Kh1 Qh3 Rg1 f5 Rcc1 Rab8 Na4 Rb4 Nc5 Be6 > >I think you are flailing a bit. > >There can be any number of things going on differently in the real game case. >You can have some problems involving transition from one position to the next, >for instance you could be leaving things in a bogus state when you terminate a >search. > >Also, when you start the program and immediately start a search, there are a lot >of memory locations that are zeroed, which might not be zeroed the second time >you start a search, and perhaps this is causing problems. > >A pure hash table problem, which would mean that you are totally off the hook >and have to do nothing, is probably not what is causing this. > >This is an important bug for you to understand. > >bruce Ok, I will go through carefully and see if there is any data not reset before a new search. James
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