Author: Miguel A. Ballicora
Date: 22:11:34 05/21/01
Go up one level in this thread
On May 21, 2001 at 07:04:51, Vine Smith wrote: >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, I think he is right. In my case I believe that I should decrease this factor. In some other positions it hurts but I did not change it because now I am working in the search. When I come back to work on the evaluation this is one thing to consider. Regards, Miguel >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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