Author: John Merlino
Date: 15:17:52 08/04/04
Go up one level in this thread
On August 04, 2004 at 15:27:46, José Carlos wrote: > In a test game, this position happened: > >[D]3r4/6k1/P5p1/1PP2p2/2Qnrb1q/1B5P/5PP1/R2R3K w - - 3 40 > > White, an old version of Shredder, was seing a7 here for some moves before, >with a plus score. At this point, at depth 11, it fails low on a7 (Qxf2 is very >strong then) and looks for another move. It chooses c6 with a plus score. Time >runs out and... c6?? > My impression is that Shredder was extending a7 (pawn to 7th), so it was >searching it a ply deeper than c6. But the refutation is the same! > A possible solution for this is not allowing extensions for the moves in the >root position. Another solution: to force another iteration after the fail low >in the root (or the idea of Sune, IIRC, of doing a depth+1 null window search >for the new root move, but only after a fail low in the root). Or even forcing >the extensions for the non PV moves at the root if the PV move was extended and >failed low. > Any experiences on the matter? > > José C. CM9_SKR on an AMD 2500 also has a tough time, waffling between a7, Qf7+ and Rf1, until it finally gives up on all of them and switches to Qd3 -- and then finally Qc3 with a score somewhat favoring White: Time Depth Score Positions Moves 0:00 1/3 2.26 4691 40.Qf7+ Kh6 41.Bd5 Qxf2 42.Bxe4 fxe4 0:00 1/4 2.02 12688 40.Qf7+ Kh6 41.a7 Qxf2 42.Rf1 Qb2 43.a8=Q Rxa8 44.Rxa8 Nxb3 0:00 1/4 2.40 17196 40.a7 Nxb3 41.Qxb3 Ree8 42.Rxd8 Qxd8 0:00 1/5 2.02 39768 40.a7 Qxf2 41.Qf7+ Kh6 42.Rf1 Qb2 43.a8=Q Rxa8 44.Rxa8 Nxb3 0:01 1/6 0.23 134683 40.a7 Qxf2 41.Qf7+ Kh6 42.a8=Q Rxa8 43.Bc4 Qg3 0:02 1/6 0.80 260771 40.Qf7+ Kh6 41.Bd5 Re7 42.Qxe7 Qxe7 43.Rxd4 Qxc5 0:03 1/6 1.10 503677 40.Rf1 Nxb3 41.Qxb3 Be5 42.Rad1 Bd4 43.a7 Qe7 0:04 1/7 0.47 764625 40.Rf1 Ne6 41.Qxe4 fxe4 42.Bxe6 Qe7 43.a7 Ra8 44.Bd5 Rxa7 45.Rxa7 Qxa7 0:08 1/8 0.47 1741606 40.Rf1 Ne6 41.Qxe4 fxe4 42.Bxe6 Qe7 43.a7 Ra8 44.Bd5 Rxa7 45.Rxa7 Qxa7 0:12 1/8 1.02 2787044 40.a7 Qxf2 41.Rf1 Qg3 42.Rxf4 Qxf4 43.Qf7+ Kh6 44.Bd5 Nf3 45.gxf3 Qxf3+ 46.Kg1 0:17 1/9 1.02 3919923 40.a7 Qxf2 41.Rf1 Qg3 42.Rxf4 Qxf4 43.Qf7+ Kh6 44.Bd5 Nf3 45.gxf3 Qxf3+ 46.Kg1 0:32 1/10 -0.32 7702479 40.a7 Qxf2 41.Rf1 Qg3 42.Rxf4 Qxf4 43.Rf1 Qc7 44.b6 Qe7 45.c6 3:01 1/10 0.27 46377979 40.Qd3 Qxf2 41.Rf1 Qh4 42.Bd5 Ne2 43.Rf3 Re5 44.a7 Bc1 45.Rf1 Ng3+ 46.Kg1 Nxf1 47.a8=Q Rxa8 48.Bxa8 3:25 1/10 0.36 52474360 40.Qc3 Be5 41.a7 Nxb3 42.Qxb3 Bxa1 43.Rxa1 Qxf2 44.b6 Re1+ 45.Rxe1 Qxe1+ 46.Kh2 Qe5+ 47.Qg3 Qxc5 48.b7 Qxa7 49.Qc7+ Kh6 50.Qxd8 Qxb7 4:20 1/11 0.36 66653164 40.Qc3 Be5 41.a7 Nxb3 42.Qxb3 Bxa1 43.Rxa1 Qxf2 44.b6 Re1+ 45.Rxe1 Qxe1+ 46.Kh2 Qe5+ 47.Qg3 Qxc5 48.b7 Qxa7 49.Qc7+ Kh6 50.Qxd8 Qxb7 jm
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