Author: Robert Hyatt
Date: 20:18:35 07/07/99
Go up one level in this thread
On July 07, 1999 at 16:02:52, pete wrote: >On July 06, 1999 at 17:15:44, blass uri wrote: > >> >>On July 06, 1999 at 13:33:01, Robert Hyatt wrote: >> >>>On July 04, 1999 at 06:19:17, Frank Schneider wrote: >>> >>>>On July 03, 1999 at 19:16:59, Gerrit Reubold wrote: >>>> >>>>>Hi all, >>>>> >>>>>please test your programs with the following position >>>>> >>>>>5rk1/1r3pp1/pp2pq2/3p4/3Q4/1PR5/P4PPP/4R1K1 w - - >>>>> >>>>>it is from a game which my program (Bringer) lost with white against The Crazy >>>>>Bishop. The draw is very easy to see (for humans): Qxf6 gxf6, and then rook >>>>>checks at h3, g3, f3... How long does your program take to find Qxf6 *with a >>>>>draw score*. How many plies / seconds? Question to the programmers: What do you >>>>>do to solve such positions fast? Extending on checks is not enough, my program >>>>>needs a 12 ply search (8 minutes on a PII-300) to find the draw (Qxf6 is found >>>>>earlier). >>>>Gromit shows a drawscore after iteration 5 (1sec). >>>> >>>>Frank >>>>> >>>>>Greetings, >>>>>Gerrit Reubold >>> >>> >>>This is an evaluation issue. If your program thinks white is better, then it >>>will see a draw. If your program likes black, then it will find that black >>>doesn't _have_ to take the draw as the repetition is certainly not forced if >>>black or white doesn't want to repeat. >> >>The repetition is forced. >>It is a perpetual check. >>I agree that a program can see the draw for the wrong reasons but it does not >>change the fact that white has perpetual check after Qxf6 gxf6. >> >>Uri > >here I am disappointed ; this is a forced perpetual ; some progs see it , some >don't , and although crafty usually is a good solver it has no clue about this >position and goes for strange king manouevres like Kf1, Ke2 , etc even at long >time controls ; crafty won't find this one at ply 15. > >some day there will be a programmer who admits something like this without >strange eexcuses :); everybody here should know that not being able to >understand a certain position doesn't say anything about the prog's overall >strength. > >Pete I believe I gave _both_ correct explanations. Crafty doesn't find it because it can't see deep enough. It sees the king walking forward on one color of squares, then walking backward on the other, which means that the rep is very deep. However, the original question was interpreted by me as something different... white can force the perp, black can not. If white thinks it is better, it can obviously avoid it if it wants... So it is all about evaluation. If one side has a really big king safety term (IE perhaps CSTal) it might like white better because of the king safety issue. And it might well turn the draw down even if it can see it. In _my_ case, I do _not_ worry about solving problems. They help little in solving games positions, because you can spend way too much time following checking lines that are futile... IE for every forced draw that Crafty walks into (with this theme) there are dozens of positions where it plays _better_ by not wasting the time following the checks.. In this game, crafty plays the "odd" Kf1 because it does _not_ want to drive the black king to where it wants to get, namely the center of the board.
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