Author: Heiner Marxen
Date: 06:21:50 09/24/00
Go up one level in this thread
On September 22, 2000 at 00:14:34, Mike Adams wrote: > Here is the position Pulsar is white in this fen string and to move. >[D]1k4r1/ppp4R/3p4/4p3/q1n1P3/1NP5/P1P2rPP/1K2Q1R1 w - - > It is a forced mate in 6 Chest cannot find any mate in 6 here. Assuming you mean black mates white, there also is no forced win for black. Here is a summery of Chest's analysis: After Ph2 - h3 ... No solution in 7 moves. After Ph2 - h4 ... No solution in 7 moves. After Pg2 - g3 ... No solution in 7 moves. After Pg2 - g4 ... No solution in 7 moves. After Pa2 - a3 ... No solution in 7 moves. After Nb3 - a5 ... Solution (in 2 moves): Qa4 : c2 After Nb3 - a1 ... No solution in 7 moves. After Nb3 - c5 ... Solution (in 2 moves): Qa4 : c2 After Nb3 - c1 ... Solution (in 2 moves): Qa4 : c2 After Nb3 - d4 ... No solution in 7 moves. After Nb3 - d2 ... No solution in 7 moves. After Rh7 - g7 ... No solution in 7 moves. After Rh7 - f7 ... No solution in 7 moves. After Rh7 - e7 ... No solution in 7 moves. After Rh7 - d7 ... No solution in 7 moves. After Rh7 : c7 ... No solution in 7 moves. After Rh7 - h8 ... No solution in 7 moves. After Rh7 - h6 ... No solution in 7 moves. After Rh7 - h5 ... No solution in 7 moves. After Rh7 - h4 ... No solution in 7 moves. After Rh7 - h3 ... No solution in 7 moves. After Rg1 - h1 ... No solution in 7 moves. After Rg1 - f1 ... Solution (in 3 moves): Qa4 - a3 After Qe1 - f1 ... Solution (in 4 moves): Rf2 : f1 After Qe1 - d1 ... No solution in 7 moves. After Qe1 - c1 ... No solution in 7 moves. After Qe1 - e2 ... Solution (in 5 moves): Rf2 : e2 After Qe1 - e3 ... Solution (in 7 moves): Nc4 : e3 After Qe1 : f2 ... Solution (in 3 moves): Qa4 - a3 After Qe1 - d2 ... No solution in 7 moves. After Kb1 - c1 ... Solution (in 5 moves): Qa4 - a3 After Kb1 - a1 ... No solution in 7 moves. Could you please state the intended solution, so that I can see who is right? >but to make it even easier for chess engines to >see this position requires a queen sacrafice on move 3 to delay it to move 6 >otherwise its mate in 4. Pulsar should need depth 5 to see this. It doesnt >process that it is in check in qsearch so after 4 moves its checkmated but it >can pass on moving in qsearch and be blind to the mate. My check extensions dont >help eathier because they look at if position is in check before move and it is >not in check or actually checkmated tell its move 5 for pulsar. Of course the >game is over then. Pulsar reported depth 6 in this position so it should have >seen it but instead it grabbed the free rook and reported a winning position >even though it had fallen into a forced mate in 6. So i did some tests. > >With Null move at R2 (depth-3) Pulsar plays Qxr untill depth 7 then it plays Kb1 >to Ka1. >With Null move at R1 (depth-2) Pulsar plays Qxr untill depth 6 then it also >plays Kb1 to Ka1. >With Null move off Pulsar plays Qxr untill depth 5 as expected then on depth 5 >it plays Knight B3 to d4. > > Whats the deal? Why is Pulsar missing a mate in 6 when it should see it in >depth 5 and it gets depth 6. Am i doing something wrong with Null Move? Is >there some trick to prevent this. I would be interested in a explanation of how >this can happen and if it happens often. > thanks Mike Adams When trying to solve a mate you should avoid Null Move completely. Others have explained the reasons already. Heiner
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