Author: Uri Blass
Date: 07:59:33 12/13/02
Go up one level in this thread
On December 13, 2002 at 10:23:12, Heiner Marxen wrote: >On December 13, 2002 at 06:03:36, Sune Fischer wrote: > >>On December 12, 2002 at 23:49:59, Uri Blass wrote: >> >>>On December 12, 2002 at 17:17:04, Dann Corbit wrote: >>> >>><snipped> >>>>>[D]k7/P2ppp2/K7/8/8/8/7P/8 w - - 0 1 >>>>> >>>>>I can see mate in 5 without calculating all the tree >>>>> >>>>>1.h4,2.h5 3.h6,4.h7,5.h8R# >>>>> >>>>>a stupid computer program(and I believe that all of the available programs are) >>>>>need to calculate a lot of lines(1.h4 f5,1.h4 f6,....) >>>> >>>>You have to calculate the square root of the nodes of the tree. Not the full >>>>tree. >>> >>>No >>> >>>In this case there is a simple plan 1.h4 2.h5 3.h6 4.h7 5.h8Q# >>> >>>It is easy to see that black can do nothing against it without calculating. >>> >>>I need only to look at class of positions and not on specific positions. >>> >>>Here is the proof of the mate in 5. >>> >>>1.h4 black has 3 pawns at f,g,h files but the pawns did not go after f5,g5,h5 >>>2.h5 black has 3 pawns at f,g,h files but the pawns did not go after f4,g4,h4 >>>3.h6 black has 3 pawns at f,g,h files but the pawns did not go after f3,g3,h3 >>>4.h7 black has 3 pawns at f,g,h files but the pawns did not go after f2,g2,h2 >>>5.h8R# >>> >>>I do not know of computers that calculates in that way but it is theoretically >>>possible to do it. >> >>I think you are using some knowledge here, that white is not mated in steps >>1.-4. If I'm not mistaken you have to prove that 1.h4 f5 does not end the game. >> >>Thus you have to examine that none of black's moves will mate white or stall >>mate black. This requires explicit search of each move and would give you a >>square root tree search. >> >>>If chest can do it then it can be faster but I have not simple idea how to >>>detect patterns like this pattern. >> >>They do simple algebra on pawn races. But that is because the programmer assumes >>the knowledge that we need to promote to win. It is not always true, you can >>mate with a pawn. > >I can assure you, that the programmer of Chest is well aware of the fact >that a pawn may deliver direct checks without a prior promotion ;-) > >Chest has a special "theory" for the case that the attacker has left just >pawns and the king. It calculates a minimum number of moves the attacker >has to perform in order to deliver a check. Trying to find an even >shorter mate is guaranteed to fail. > >For the defender side Chest assumes a very simple strategy: the king will >move between two squares. As long as we can show that that will remain >to be a legal move, the defender cannot possibly be mated. In this case the defender(black) has no legal moves with the king but only with the pawns. > >No moves are executed, no trees are examined, Chest just examines where >the remaining pawns may be pushed to, and whether that may disturb the >primitive strategy of the defender, by calculating distances between >the pawns possible target squares and the defender king. > >In some positions this helps Chest to reach much larger depths. > >Cheers, >Heiner I do not understand the strategy of chest here 1)Does chest generates a tree to prove no mate in 4 here? (the black king has no moves unless white moves with the king) 2)Does chest generates a tree with all the possible alternatives for the defender to prove mate in 5(again it is not needed because all alternatives are eqvivalent because black cannot promote a pawn or threat check and there is no stalemate)? Uri
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