Author: Uri Blass
Date: 04:00:18 03/07/06
Go up one level in this thread
On March 07, 2006 at 06:24:15, Kolss wrote: >On March 07, 2006 at 02:44:23, Uri Blass wrote: > >>On March 06, 2006 at 21:14:43, Stuart Cracraft wrote: >> >> >teedee - Temporal Differences Chess >>>v1 2006 >>>copyright (c) 2004,2005,2006 >>>Stuart Cracraft (cracraft@cox.net) >>> >>>*** Problem Solution(s): Qg6 (bm) >>>[D] 2rr3k/pp3pp1/1nnqbN1p/3pN3/2pP4/2P3Q1/PPB4P/R4RK1 w - - bm Qg6 >>> 1/ 9 e5c6 -2690 0.01 565 e5c6 d6c6 >>> 2/10 f6h5 -2828 0.04 2488 f6h5 c6e5 d4e5 >>> 3/10 f6h5 -2586 0.07 5370 f6h5 d6f8 >>> 4/10>f6h5 -2185 0.08 5945 f6h5 d6f8 e5c6 b7c6 h5f4 >>> 4/13 f6h5 -2003 0.15 13003 f6h5 g7g6 h5f6 c6e5 d4e5 >>> 5/14>f6h5 -1602 0.18 14952 f6h5 g7g6 h5f6 c6e5 d4e5 d6e5 >>> 5/17 f6e8 1127 0.41 37600 f6e8 d6e5 d4e5 d8e8 >>> 6/21>f6e8 1527 0.91 90041 f6e8 d6e5 d4e5 d8e8 f1f7 e6f7 >>> 6/21 Mg3g6 99988 0.96 94722 g3g6 d6f8 e5f7 e6f7 g6h7 >> >>I wonder why your program need depth 6 to see the solution that is mate in 2. >> >>I think that you should try to look at the tree to see the lines that it >>searched after g3g6 >> >>Movei needs only 2 plies for this problem. >> >>After Qg6 and black move qsearch finds the mate. >> >>I know that you have not checks in the qsearch but even without checks in the >>qsearch I see no logical reason to have depth 6. >> >>I wonder if null move prevents you to see it earlier or there is another reason. >>How many plies do you need to solve this position if you disable null move >>pruning? >> >>I believe that you use null move with R=2 so I think that even if null move >>prevents you to see the mate at depth 3 you should see it at least at depth 4 >>thanks to check extension. >> >>Qg6 Null Qh7+ is exactly 4 plies if you use R=2 >> >>Qg6 Null Qh7+ should be extended thanks to check extension so even with no >>function that tell you if a position is a mate you should see a mate score. >> >>Maybe one of your problems is that you do not extend checks when the remaining >>depth is 0 but do it only when the remaining depth is more than 0. >> >>If this is the case then >>I suggest that when the remaining depth is 0 before going to qsearch you check >>if the king of the side to move is under threat and add one ply to the depth so >>you do not go to qsearch in this situation. >> >>Uri > > >Hello, > >This answer somewhat goes along with Uri's comment, so I placed it as an answer >to his post... > >There are several scenarios what a search could do in this MATE in 2 position. I >list a few: > > >SCENARIO 1: null move R=2, no checks in quiescence search (QS), no futility >pruning: > >Ply 4: >Remaining depth (D) = 4 >1. Qg6 => D = 3 >1. ... null => D = 0 >white goes to QS: eval possible (probably) worse than for other moves (such as >1. Ne8); try captures such Nxc6 which do not give a better score than alpha; 2. >Qh7# is NOT TRIED, as it is a quiet move. >MOVE IS NOT FOUND. > >Ply 5: >D = 5 >1. Qg6 => D = 4 >1. ... null => D = 1 >2. Qh7# (assuming here that the checkmate is recognized in QS! - make sure that >black cannot stand pat here, but is forced to try all evasion moves until one >causes a cut-off; if there are no moves, return checkmate!) => null move refuted >with mate threat >1. ... fxg6 => D = 4 (3 + 1 for mate threat) >2. Qh7# >[...] >MOVE IS FOUND. Yes You are right With R=2 it is 5 plies and not 4 plies. R=2 means that null is 3 plies and not that null is 2 plies as my reply suggested. Still 6 plies seem to me too big and I suspect that his program simply look at Qg6 Null Qh7# and does not evaluate it as mate at depth 5. Uri
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