Author: Robert Hyatt
Date: 21:14:18 01/19/01
Go up one level in this thread
On January 19, 2001 at 21:33:08, John Merlino wrote: >On January 19, 2001 at 17:23:03, Scott Gasch wrote: > >>Hi all, >> >>Here's a pretty simple test position. This comes from the WAC suite... my >>engine does fairly well on this suite as a whole but seems blind to this >>solution. >> >>[D]8/7p/5k2/5p2/p1p2P2/Pr1pPK2/1P1R3P/8 b - - >> >>The solution is Rxb2 -- black's connected passers are unstoppable after the >>recapture. >> >>My program refuses to find this solution... even at 9 ply it misses it. The >>strange thing is that from the other side after Rxb2 it sees that white is toast >>very quickly... score dropping to -500 or so after about 1 second. >> >>My question is, of course, how this move is missed. I've tried kicking up the >>value of connected passers and passed pawns in general. I've tried adding a >>special rule to eval about connected passers on the 7th, on move, with control >>of a queening square. I've tried cutting back my futility margin in qsearch and >>always extending a full ply for checks (It usually extends only 3/4 ply for >>checks after the iteration depth). And still it does not find Rxb2. >> >>Even stranger is if I run a static eval with the two connected passers rolling >>towards the queening square after the rook exchange the eval puts black ahead! >>I can't seem to figure this out... either my pruning is too aggressive or there >>is some other bug in the engine...? >> >>I hope someone out there can give me a little advice. Thanks! >> >>Scott > >Just to make things difficult, Chessmaster 8000 seems to have this one's number, >AND it reports the correct move at ply 9, despite other postings here that have >stated that it should take somewhere between 12 and 14 plies to find the result. >Just thought you'd like another engine's opinion: > >Time Depth Score Positions Moves >0:00 3 -0.99 555 1... Rb8 2. e4 fxe4+ 3. Kxe4 Rd8 >0:00 3 -1.03 1215 1... c3 2. bxc3 Rxc3 3. Ra2 Rc2 >0:00 4 -1.03 1588 1... c3 2. bxc3 Rxc3 3. Ra2 Rc2 >0:00 4 -1.10 1979 1... Rb8 2. e4 fxe4+ 3. Kxe4 Re8+ > 4. Kf3 Rd8 >0:00 5 -1.08 3917 1... Rb8 2. e4 fxe4+ 3. Kxe4 Rd8 > 4. Ke3 Kf5 >0:00 5 -1.09 5180 1... Rb6 2. e4 fxe4+ 3. Kxe4 Rd6 > 4. Ke3 Kf5 >0:00 6 -1.09 12974 1... Rb6 2. e4 fxe4+ 3. Kxe4 Re6+ > 4. Kf3 Rd6 5. Ke3 Kf5 >0:00 7 -1.03 34638 1... Rb6 2. e4 fxe4+ 3. Kxe4 Re6+ > 4. Kd4 Re2 5. Rd1 Rxh2 6. Kxc4 >0:01 8 -1.03 119652 1... Rb6 2. e4 fxe4+ 3. Kxe4 Re6+ > 4. Kd4 Re2 5. Rd1 Rxh2 6. Kxc4 >0:02 8 -1.08 216622 1... Rb8 2. e4 fxe4+ 3. Kxe4 Rd8 > 4. h4 h5 5. Ke3 Kf5 >0:03 9 -1.03 370922 1... Rb8 2. e4 fxe4+ 3. Kxe4 Rd8 > 4. Ke3 Re8+ 5. Kd4 Re2 6. Rd1 Rxh2 > 7. Kxc4 >0:08 9 -1.99 883082 1... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kd7 6. Rb7+ > Kc6 7. Rf7 c2 8. Rf6+ Kd7 9. Rxf5 > c1=Q 10. Rd5+ Ke6 11. Rxd3 >0:20 10 -3.08 2060992 1... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kd7 6. Rb7+ > Kc8 7. Rxh7 c2 8. Rh8+ Kd7 9. Rh7+ > Kd6 10. Rh6+ Kd5 11. Rf6 c1=Q 12. > Rxf5+ Kc4 13. h4 Qxa3 >0:56 11 -3.74 5510399 1... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kc5 6. Rb7 > c2 7. Rxh7 d2 8. Rc7+ Kd6 9. Rxc2 > d1=Q+ 10. Re2 Qd3 11. h4 Qxa3 > >jm I think you misunderstood the 14 ply reference. You have to search about 14 plies deep along the critical line to find the win. But if you extend the right things, you can find it quicker. I see the tactical win here at 12 plies if I disable the connected passer code. Otherwise I see it way sooner for evaluation reasons. CM has always had a pretty good search extension approach to handling tactical things, which could solve this much quicker than normal without surprising me one bit. But you have to look at the critical line deep enough to get out of the series of checks and then promote the pawn. CM probably does that better than anybody...
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