Author: Vine Smith
Date: 04:04:51 05/21/01
Go up one level in this thread
On May 21, 2001 at 02:05:10, Miguel A. Ballicora wrote: >On May 21, 2001 at 01:15:18, Vine Smith wrote: > >>On May 20, 2001 at 18:53:46, Miguel A. Ballicora wrote: >> >>>On May 20, 2001 at 14:47:12, Christophe Theron wrote: >>> >>>>On May 20, 2001 at 14:26:15, Vine Smith wrote: >>>> >>>>>On May 20, 2001 at 13:24:29, Christophe Theron wrote: >>>>> >>>>>>On May 20, 2001 at 04:25:41, Frank Phillips wrote: >>>>>> >>>>>>>On May 19, 2001 at 23:48:48, Christophe Theron wrote: >>>>>>> >>>>>>>>On May 19, 2001 at 23:37:31, Ratko V Tomic wrote: >>>>>>>> >>>>>>>>>>I'm extremely surprised that my creature managed to survive more >>>>>>>>>> than 30 moves, given a 300 times speed handicap. >>>>>>>>> >>>>>>>>>The flip side is that the current programs running at some >>>>>>>>>future machines at 300 GHz won't be able to crush the current >>>>>>>>>programs on 1 GHz any more convincingly (in terms of how >>>>>>>>>many moves the slower machine can hang on) than what happened >>>>>>>>>in this matchup. >>>>>>>>> >>>>>>>>>This is the same effect that many players have experienced >>>>>>>>>when upgrading their hardware to 2-3 times faster one and >>>>>>>>>then being disapponted, after all the expense and hopes, >>>>>>>>>when they can't even notice any difference in the perceived >>>>>>>>>program strength (aginst humans). >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>You are absolutely right. >>>>>>>> >>>>>>>>I think we are already beginning to experience the effects of dimishing returns >>>>>>>>in chess on current hardware at long time controls. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Christophe >>>>>>> >>>>>>>Would someone take the time to explain this simply and clearly, to me. I can >>>>>>>understand that if you are already beating humans (or some other group of >>>>>>>players) most of the time, then increasing the speed still means you are beating >>>>>>>them most of the time and maybe a bit more, but until a machine can see _all_ >>>>>>>there is to see how would it not improve by seeing more and how can you say >>>>>>>(apriori) that it will improve only at a diminishing return? In other words, I >>>>>>>can believe that results against a set of players is aysomtopic, tending towards >>>>>>>100 percent, but do see why this is necessarily true of the game played by two >>>>>>>otherwiseequally matched entities. >>>>>> >>>>>> >>>>>> >>>>>>In my opinion it has to do with the fact that in a given chess position the >>>>>>number of moves is limited. Generally you have between 20 and 50 legal moves. >>>>>> >>>>>>From these moves, only an even more limited subset does not lead to an obvious >>>>>>loss. >>>>>> >>>>>>And from this subset there is an even more limited subset of moves (2 or 3 >>>>>>generally) that can be played, and chosing between them is a matter of >>>>>>preference because the amount of computation needed to prove which one is better >>>>>>is too big for any computer. >>>>>> >>>>>>So once you reach the stage where you can see which 2 or 3 moves are playable, >>>>>>it would take an additional huge computation to see further. >>>>>> >>>>>>I think some chess programs on current computers at long time controls have >>>>>>already reached this stage, and this is why is becomes increasingly difficult to >>>>>>say which one is better. >>>>>> >>>>>>This is a very simplistic explanation which lacks mathematical support, I know, >>>>>>but that's how I explain dimishing returns. >>>>>> >>>>>> >>>>>> >>>>>> Christophe >>>>> >>>>>Is it possible that there is also a problem with bad evaluations infecting whole >>>>>branches in the tree of analysis? In Fritz vs. Gambit Tiger at Leiden, Fritz >>>>>played 21.b4, shutting in its queen. Was this not a dreadful move? Yet, I had >>>>>Fritz analyze after this point through 18 ply, and the evaluation was just +0.06 >>>>>(after which it mysteriously halted analysis). And Tiger 14 has reached 20 ply >>>>>looking at this same position, with an evaluation of just +0.46 after 21...Nc3 >>>>>22.Rd3 Qf6 23.Kf1 Ne4 24.Bd4 Qf7 25.Bb2 g5 26.Rde3 Bf4 27.Bxe4 fxe4 28.Rxe4 Rxe4 >>>>>29.Rxe4 Qxd5 30.Re7. Actually, the final position is lost for White after >>>>>30...Qd3+ 31.Re2 Qb1+ 32.Ne1 Bf5, but White doesn't need to play 30.Re7. The >>>>>point is that neither program, given even 10-12 hours to think (on a PIII 850) >>>>>appreciates the disastrous effects of White's missing queen. As poor evaluations >>>>>like this clog up the search, all lines begin to look like one another, despite >>>>>huge differences between them that would be clear to any human player examining >>>>>these positions. >>>>>Regards, >>>>>Vine Smith >>>> >>>> >>>> >>>>I do not agree. >>>> >>>>Tiger KNOWS about the bad position of the Queen after b4 and would never play >>>>this move. >>>> >>>>If you try, you will see that Tiger's evaluation is different in the lines the >>>>queen is trapped and in the lines it is not. >>>> >>>>The evaluation difference is not big, but it is enough to avoid such a >>>>disastrous move in almost all the cases, and to try to find a way to free the >>>>queen if it happens to be trapped by a long sequence of forced moves. >>>> >>>>Tiger is able to identify some cases of blocked pieces or pieces with poor >>>>mobility in its evaluation. In particular, it is able to see that the queen is >>>>blocked after b4? and gives a penalty for this. I have worked hard in this part >>>>of the evaluation, so I can't let you generalize and say that any program would >>>>ignore the consequences of the trapped queen. Mine knows. >>> >>>Even mine knows :-) Yes, my program sucks but my point is that it is a matter >>>of tuning the evaluation, it is now mission impossible. >>> >>>Vine, I post the results before in case that you miss the post (it is easy >>>with so much traffic) >>> >>>http://www.icdchess.com/forums/1/message.shtml?170629 >>> >>>Regards, >>>Miguel >>> >>>> >>>> >>>> >>>> Christophe >>Hi -- >>I did miss it -- thanks for referring me to the message, because I was glad to >>finally see an evaluation that more or less matches my perception of the >>disastrous nature of 21.b4. I must certainly do some testing with Gaviota, to >>see if this positional sense it displays here is reflected in its evaluation of >>other positions. Also, Gaviota's preferred 21.Re2 was my first thought when >>looking for alternatives to 21.b4. I'm baffled by not only Fritz's choice, but >>also the number of programs that think 21.b3 is the best idea here. I don't see >>problems with the b-pawn; if there are any, then Crafty's choice of 21.Bc1 has >>to be superior to moving the pawn, which just creates additional weaknesses. >>Regards, >>Vine > >Gaviota is a *weak* winboard engine in development. If Gaviota can beat fritz in >this position, it will prove a point about that the position is disastrous. I >can assure you that gaviota will try to keep the queen trapped. I do not have >Fritz, otherwise I will try it myself. Gaviota has some kind of learning >implemented, so you can even play a match. I believe that the position >is so bad that I won't be easy for Fritz... > >If you want to download it, it is in > >http://www.msu.edu/~ballicor/gav > >Regards, >Miguel >PS: let me know if you try it. I downloaded Gaviota right after seeing the evaluation, as I had seen your post at the Winboard forum about the new version 2.2, and used that to hop to your site. Christophe made an interesting point about the scoring of evaluations in a parallel thread -- might it actually hurt the program to have this set too high, even though the "true" penalty for the trapped queen might be a pawn or more? It's a possibility, I suppose, although it makes the interpretation of evaluations very difficult if the scoring of such factors is deliberately suppressed. How do I tell (if I can't make the determination myself) if a program is doing just "pretty good" with an eval of +0.50, and when a program is totally winning with the very same eval? Matching Gaviota against Fritz here is a great idea -- I will definitely do this, since Uri Blass noted that such matches could contribute towards an understanding of how much trouble White is (or isn't) in. Since it's clear that Gaviota values the queen's immobility highly, Fritz will only be able to liberate it with tactical shots due to outsearching, the instances of which should not be hard to identify. But I'm not sure that Fritz will be so interested in doing that, as its analysis of the position after 21.b4 included no attempts to play a4 at any point, and its evaluations certainly didn't indicate that it felt there was anything troublesome about its stranded queen. I'll keep you updated about the match. Regards, Vine
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