Author: Uri Blass
Date: 08:36:16 05/22/04
Go up one level in this thread
On May 22, 2004 at 09:49:18, Sune Fischer wrote: >On May 22, 2004 at 08:17:11, Bas Hamstra wrote: > >>On May 21, 2004 at 20:30:53, Dann Corbit wrote: >> >>>On May 21, 2004 at 20:25:04, Uri Blass wrote: >>> >>>>On May 21, 2004 at 20:17:21, Mike Byrne wrote: >>>> >>>>>On May 21, 2004 at 19:32:33, George Tsavdaris wrote: >>>>> >>>>>>Black threatens mate and white's Queen. What white should play? >>>>>>Give it's Queen of course! Qf4!! and white is winning. >>>>>> >>>>>> Impressive for humans but not for computers, as any chess engine can solve >>>>>>this in seconds.... >>>>>> >>>>>>[D]1kbr3r/pp6/8/P1n2ppq/2N3n1/R3Q1P1/3B1P2/2R2BK1 w - - 0 1 >>>>> >>>>> >>>>>Black(1): mt 24 >>>>>max threads set to 2 >>>>>Black(1): 1kbr3r/pp6/8/P1n2ppq/2N3n1/R3Q1P1/3B1P2/2R2BK1 w - - 0 1 >>>>>White(1): go >>>>> clearing hash tables >>>>> time surplus 29.92 time limit 1666:39 (1666:39) >>>>> depth time score variation (1) >>>>>starting thread 1 >>>>> 1 0.00 2.84 1. Qxc5 >>>>> 1-> 0.00 2.84 1. Qxc5 >>>>> 2 0.00 -1 1. Qxc5 >>>>> 2 0.00 -Mat01 1. Qxc5 Qh1# >>>>> 2 0.00 -9.26 1. Qe5+ Nxe5 2. Nxe5 Rxd2 3. Rxc5 >>>>> 2 0.02 -8.25 1. Bg2 Nxe3 2. Rxe3 >>>>> 2-> 0.02 -8.25 1. Bg2 Nxe3 2. Rxe3 >>>>> 3 0.02 -8.25 1. Bg2 Nxe3 2. Rxe3 >>>>> 3-> 0.04 -8.25 1. Bg2 Nxe3 2. Rxe3 >>>>> 4 0.04 -8.62 1. Bg2 Nxe3 2. Rxe3 Qh2+ 3. Kf1 Nd3 >>>>> 4-> 0.05 -8.62 1. Bg2 Nxe3 2. Rxe3 Qh2+ 3. Kf1 Nd3 >>>>> 5 0.07 -8.58 1. Bg2 Nxe3 2. Rxe3 Nd3 3. Rc2 >>>>> 5 0.07 -8.29 1. Qf4+ gxf4 2. Bxf4+ Ka8 3. Nb6+ axb6 >>>>> 4. axb6+ Na6 5. Rxc8+ Rxc8 6. Rxa6+ >>>>> bxa6 7. Bg2+ Rc6 8. Bxc6# >>>>> 5-> 0.08 -8.29 1. Qf4+ gxf4 2. Bxf4+ Ka8 3. Nb6+ axb6 >>>>> 4. axb6+ Na6 5. Rxc8+ Rxc8 6. Rxa6+ >>>>> bxa6 7. Bg2+ Rc6 8. Bxc6# (s=9) >>>> >>>> >>I don't agree at all. IMO it's kind of ridiculous to let a PV end in checkmate >>without showing a mate score. What is happening here is that Crafty doesn't have >>a clue about the checkmate (because of how it's qsearch operates) and so does >>not evaluate it. However the PV print routine DOES recognize it. > >You can't trust a PV ending in mate if the score has not been passed through the >tree. >In general it is possible that black could have found something better than Rc6 >had he seen it lead to a mate. Black saw it otherwise it could not write the pv with mate score. Maybe it did it only after calculating the pv in the function that print the pv but the question is what is the reason not to do it in every node. I think that knowing if the side to move is in mate or not in mate should be part of the evaluation function. Note that detecting that the side to move is not in mate is very often cheap because you can know that a move does not threat the king based only on the from and to squares. Uri
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