Author: Uri Blass
Date: 11:35:08 03/07/04
Go up one level in this thread
On March 07, 2004 at 13:46:41, Anthony Cozzie wrote: >On March 06, 2004 at 17:06:23, GeoffW wrote: > >>Hi >> >>Here is a position I found interesting, white has just played Rf6, black to move >> >>[D]r3qnk1/rb2bppp/4pR2/pp1pP1PP/2pP3N/P1P1P1Q1/1PB5/4B1RK b - - 0 1 >> >>My programs analysis for this position is horrid >> >>Ply Eval Time Nodes Principle Variation >> 1 433 0 17 g7f6 e5f6 >> 2 433 0 290 g7f6 e5f6 >> 3- 393 1 4782 g7f6 >> 3 204 1 8053 e7a3 b2a3 g7f6 e5f6 >> 4 204 3 18575 e7a3 b2a3 g7f6 e5f6 >> 5 204 6 44876 e7f6 g5f6 g7g6 h4f3 f8d7 h5g6 h7g6 >> 6 192 10 97670 e7f6 e5f6 g7g6 h5g6 h7g6 h4f3 >> 7 194 21 193103 e7f6 e5f6 g7g6 h4f3 a8d8 h5g6 h7g6 >> 8 187 60 564304 e7f6 e5f6 g7g6 h4f3 g6h5 g3h4 f8d7 h4h5 >> 9 188 132 1263805 e7f6 e5f6 g7g6 h4f3 f8d7 e1d2 a8b8 g3h2 e8d8 >>10 176 396 3783030 e7f6 e5f6 g7g6 h4f3 f8d7 g3h2 a8d8 e1g3 d7b6 f3e5 >>11 176 942 8062241 e7f6 e5f6 g7g6 h4f3 e8c6 g3h2 f8d7 e1g3 a8d8 f3e5 >>d7e5 g3e5 >>12- 136 3984 35236639 e7f6 >>12 102 144954 868931003 b5b4 a3b4 a5b4 f6f4 a7a2 g3g2 b4b3 c2b1 a2a1 e1d2 >>f8d7 e3e4 >> >>It firstly thinks it has won a rook by taking it with Pxf6, then it realises >>this is bad, and avoids the Rook sacrifice by coming up with its own weird >>bishop sacrifice Bxa3. Two plies later then decides it had better take the rook >>after all with the obvious looking Bxf6. It takes 40 seconds to get to ply 12 >>before it realises that this is also a hopeless losing move. >>Then it takes almost 25 minutes to resolve the fail low with a branching factor >>of 24 !! >>I am not sure why it struggles to resolve this specific fail low so badly, this >>is probably the trickiest fail low I have seen so far, at least for my program. >>It was taking so long I was convinced it was locking up in an infinite search >>bug. I guess it probably isnt a bug as it finally does come up with a reasonable >>move, all be it far too late. >> >>What do other programs make of this, daresay Crafty et al. will have it all >>worked out and resolved in about 5 seconds flat ;-( >> >>P.S it finally managed ply 13 as I was typing this up >> >>13 102 327723 2072998497 b5b4 a3b4 a5b4 f6f2 b4b3 c2b1 f8d7 e1d2 a7a1 h5h6 >>g7g6 h4f3 a8a7 >> >>54 minutes to decide white is a pawn up after avoiding the sac. >> >> Regards Geoff > > >Working out fail lows always takes a long time :( > >Zappa needs 1.4 seconds (opteron 1.8) to avoid Be7xf6 (gxf6 is only played by >the q-search ;) I think black is in some trouble here though: > >1... Be7xf6 2. g5xf6 g7-g6 3. Qg3-g5 Nf8-d7 4. h5xg6 h7xg6 > = (0.90) Depth: 7/10 00:00:00.13 62650kN >1 ...Be7xf6-- > - (0.65) Depth: 8/9 00:00:00.14 64878kN >1 ...Be7xf6-- > - (0.65) Depth: 8/9 00:00:00.38 163136kN >1... Be7xf6 2. g5xf6 g7-g6 3. Qg3-g5 Nf8-d7 4. h5xg6 h7xg6 5. Nh4xg6 > = (-0.86) Depth: 8/12 00:00:00.40 176097kN >1... Bb7-c6 2. Rf6-f2 Qe8-d8 3. h5-h6 g7-g6 4. Nh4-f3 Nf8-d7 5. Rg1-f1 > = (-0.54) Depth: 8/14 00:00:01.31 592471kN >1... b5-b4 2. a3xb4 a5xb4 3. Rf6-f1 b4-b3 4. Bc2-b1 Ra7-a1 5. Be1-d2 > = (0.26) Depth: 8/14 00:00:03.07 1503664kN >1... b5-b4 2. c3xb4 a5xb4 3. Be1xb4 Be7xb4 4. a3xb4 Bb7-c6 5. Rf6-f1 Qe8-e7 6. >g5-g6 f7xg6 7. h5xg6 h7-h6 8. Qg3-e1 > = (-0.69) Depth: 14/25 00:04:59.46 217960622kN > >(score = white up .7) > >Top programs will get this one with eval I think. > >anthony I think that you overestimate the top programs. I think that the search is the main advantage of them. I guess that all of them see advantage for black at small depth and suggest Bxf6 at small depth. Uri
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