Author: Anthony Cozzie
Date: 14:59:25 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. I think this is just a tough position, but some of it is pawn eval v kingsafety. In this case it looks like the king attack is stronger than the passers, but it is just a tough position. Zappa doubts a _lot_ on this one. 1x1.8 1. Qc4-c3 Qh4xf2 2. Rd1-f1 Qf2-e3 3. Qc3xe3 Bf4xe3 4. a6-a7 Nd4xb3 5. a7-a8=Q Rd8xa8 6. Ra1xa8 Be3xc5 = (-0.37) Depth: 13/30 00:04:10.98 194590kN (775 KN/s, 0 splits, 0 2x1.8 1. Qc4-c3 Qh4xf2 2. Rd1-f1 Qf2-e3 3. Qc3xe3 Bf4xe3 4. a6-a7 Nd4xb3 5. a7-a8=Q Rd8xa8 6. Ra1xa8 Be3xc5 = (-0.37) Depth: 13/30 00:02:18.48 213321kN (1540 KN/s, 955 splits, 133 aborts) 1. Qc4-c3 Qh4xf2 2. Rd1-f1 Qf2-e3 3. Qc3xe3 Bf4xe3 4. Ra1-d1 Nd4-e2 5. Rd1xd8 Ne2-g3 6. Kh1-h2 Ng3xf1 7. Kh2-h1 Be3xc5 8. Rd8-d7 Kg7-h6 = (-0.22) Depth: 14/30 00:03:11.61 296222kN (1546 KN/s, 1240 splits, 146 aborts) Speedup is only 81% :( anthony
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