Author: Andrew Williams
Date: 14:13:49 03/06/04
Go up one level in this thread
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 Hi Geoff, Do you print out the number of extensions of various kinds that your program has made during a search? That might be helpful in seeing what is going on here. Andrew
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