Author: Robert Hyatt
Date: 22:22:57 09/12/02
Go up one level in this thread
On September 12, 2002 at 22:56:12, James Swafford wrote: > >I'm (still) working with my hash tables, and having quite a time >with this one. I'm hoping someone can explain this behavior: > >1. In iteration 1, the search returns a score of 15 for move A. >2. Naturally, the iteration 2 search begins with move A. The search > window is set to +/- 1 pawn ==> -85, 115. (Yes, that's wide, > but that's not the point. :) >3. Move A again gets a score of 15 from the depth 2 search. > The search continues, though, and root move B fails high. > Move B is a move that leads to mate in 3 (half moves), so > an extension was triggered (I don't think this is important). >4. The iteration 2 search is restarted with a wider window of > +/- infinity. >5. Move A immediately gets researched and, after one node, > gets a score of 15 (no problem so far). why do this? Why not just start searching on the move that failed high? you already know the score for the previous best move. And you have already dismissed all the moves between that move and the fail high move as inferior, so why go again??? It will waste a _bunch_ of time. >6. Iteration 2 finished, and move A is the pv move. Move B, > the move that caused the fail high earlier, has a _very_ > negative score of -675. And it's supposed to be mate in 3. >7. Steps 2-5 are repeated for iteration 3. >8. Move B gets a score of CHECKMATE-3 (mate in 3), and replaces > move A in the pv. > >This is a hashing issue. If I clear the hash table after failing >high at the root, move B is found at iteration 2 with the proper >score of mate in 3. > >I'm stumped. Can anybody offer an explanation? Search output >below if it'll help. :) > Do you adjust the hash score for mates? >-- >James > >Problem 1: >r1bq2rk/pp3pbp/2p1p1pQ/7P/3P4/2PB1N2/PP3PPR/2KR4 w - - h6h7; > >parsing: h6h7...done. >correct move(s): h6h7 >FW Dpth Nd Cnt CSecs Score PV Line > 1& -> 15 0 -570 h6g7 g8g7 > 1& -> 216 5 10 h6g5 g6h5 > 1& -> 589 5 15 h6f4 d8e8 >before sort... >Move list: >h6g7(-570) h6g6(-675) h6g5(10) h6f4(15) h6e3(10) h6d2(10) h6h7(-675) h5g6(-580) >d4d5(-880) c3c4(-880) d3c4(-885) d3b5(-885) d3a6(-885) d3e2(-885) d3f1(-885) >d3c2(-885) d3b1(-885) d3e4(-885) d3f5(-885) d3g6(-775) f3e5(-875) f3g5(-885) >f3h4(-895) f3d2(-885) f3e1(-895) f3g1(-900) a2a3(-880) a2a4(-875) b2b3(-880) >b2b4(-875) g2g3(-880) g2g4(-875) h2h1(-885) h2h3(-885) h2h4(-885) c1c2(-770) >c1d2(-885) c1b1(-770) d1e1(-885) d1f1(-885) d1g1(-885) d1h1(-885) d1d2(-885) > > 1 -> 2299 16 15 h6f4 d8e8 > 2& -> 3373 16 15 h6f4 d8f6 f4f6 > 2& -> 6558 27 +++ h6h7 > 2& -> 6559 27 15 h6f4 d8f6 >before sort... >Move list: >h6f4(15) h6g5(5) h6e3(10) h6d2(10) h6g7(-555) h5g6(-85) h6g6(-670) h6h7(-675) >c1c2(-85) c1b1(-85) d3g6(-1100) f3e5(-880) a2a4(-880) b2b4(-880) g2g4(-880) >d4d5(-895) c3c4(-885) a2a3(-885) b2b3(-885) g2g3(-885) d3c4(-890) d3b5(-1195) >d3a6(-1180) d3e2(-890) d3f1(-890) d3c2(-890) d3b1(-890) d3e4(-890) d3f5(-1190) >f3g5(-985) f3d2(-885) h2h1(-885) h2h3(-885) h2h4(-885) c1d2(-890) d1e1(-885) >d1f1(-885) d1g1(-885) d1h1(-885) d1d2(-885) f3h4(-985) f3e1(-900) f3g1(-905) > > 2 -> 26715 60 15 h6f4 d8f6 > 3& -> 31482 66 20 h6f4 g6h5 f4f7 g7h6 > 3& -> 73074 115 +++ h6h7 > 3& -> 73075 115 20 h6f4 g6h5 > 3& -> 97128 148 59997 h6h7 h8h7 h5g6 >before sort... >Move list: >h6f4(20) h6e3(0) h6d2(0) h6g5(5) h5g6(-580) c1c2(-650) c1b1(-650) h6g7(-555) >h6g6(-660) h6h7(59997) f3e5(-880) a2a4(-885) b2b4(-885) g2g4(-885) c3c4(-890) >a2a3(-890) b2b3(-890) g2g3(-890) f3d2(-890) h2h1(-895) h2h3(-895) h2h4(-895) >d1e1(-895) d1f1(-895) d1g1(-895) d1h1(-890) d1d2(-885) d3c4(-895) d3e2(-895) >d3f1(-895) d3c2(-895) d3b1(-895) d3e4(-895) c1d2(-895) d4d5(-895) f3e1(-905) >f3g1(-910) f3g5(-985) f3h4(-995) d3g6(-1100) d3a6(-1180) d3f5(-1185) d3b5(-1195) > > 3 -> 205158 258 59997 h6h7 h8h7 h5g6 > >nodes -> total: 205158; nps: 79518; csecs: 258 > int: 41013; frontier: 75894; quiesce: 164145 >hash -> fh: 1286 (3); fl: 170 (0); ex: 22592 (55) > hash mvs played: 4837 >mv ord -> fh 1st mv: 94(12822 cuts, 12147 1st mv); avg bf: 8.650 >ext. -> one rep: 444; pp: 351; recap: 9114 > >move h6h7 >CORRECT
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