Author: Ernst Walet
Date: 07:13:01 11/21/97
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On November 21, 1997 at 07:50:35, Chris Whittington wrote: > >On November 20, 1997 at 23:55:56, Howard Exner wrote: > >>Here are 5 positions to test on your computer programs. The theme >>is how to play when the bishop is the opposite color of the queening >>square. >> >>k7/pp6/8/P7/3K4/P7/P4B2/8 w - - id"a3-a4 - Wrong Bishop" bm a3 a4; >>5k2/8/7P/8/8/8/K6P/1B6 w - - id"B-h7 - Wrong Bishop" bm b1h7; >>8/7p/6p1/3k4/B5PP/8/8/1K6 w - - id"a4e8 - Wrong Bishop" bm a4e8; >>8/6p1/8/3kP2P/6K1/8/8/2b5 w - - id"h5-h6 - Wrong Bishop" bm h5h6; >>8/8/pp6/3b2K1/1P6/PN2k3/8/8 w - - id"Na5 draw - Wrong Bishop" bm b3a5; >> >>The first three are wins and the last two are draws. >> >>I tested these on Rebel 8. The results are: >> >>K6-233 60Mb Hash >> >>1. Not solved by 15:00 >>2. 0:51 >>3. 0:16 >>4. 0:21 >>5. Not solved by 15:00 >> >>Problems 1 and 5 are difficult for Rebel 8. A known issue >>with Rebel 8 is it's difficulty with doubled pawns on the a >>or h files. An old Maresch test position uncovered this. >> >>Could others post some of there results for these 5 problems. >>Maybe 1 and 5 are difficult for all programs? > >CSTal version 287_d, P6 200, 16 Mb hash > >1. a4 33s >2. Bh7 0s >3. Be8 86s >4. h6 30s >5. unsolvable > >positions 1-4 are all solvable with the knowledge programmed in. >Basically the prg needs to know that the king can get to cover the >queening square in time; but there are some tricky sepcial cases to >consider. 1-4 are examples where search alone will tale quite soem time, >if ever, to reach the solution. > >its an issue of time spent: > >a) coding >b) slowing up the program by looking for the knowledge >c) getting the special cases right (else you'll lose drawn positions, >and draw won positions. > >5. is semi-unsolvable. Its virtually unsolvable by search, and its also >unsolvable by 'normal' knowledge and search. You would need the very >special case knowledge that to win the black king must run off and >capture the white rook file pawns; this diversion would then allow the >white king to cover the queening square. I wouldn't like to have to code >this sort of knowledge, not even for $1,000,000. But without such >knowledge, and with the 'normal' knowledge; search doesn't really help; >search finds the problem fairly quickly, but horizons it away by keeping >the black king in the centre (holds off the white king), and wiggles >around the bishop - this horizoning can go on for many many plys. > >Chris Whittington ChessGenius 3 solves pos. 5 in 1:28 on a 486/66 with 7MB hash. I watched for 10 minutes and it stays with Na5.
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