Author: blass uri
Date: 04:27:51 07/29/00
Go up one level in this thread
On July 29, 2000 at 06:57:38, Stephen A. Boak wrote: >On July 29, 2000 at 06:02:41, blass uri wrote: > >>I understand the ELO system. > >No you don't--based on what I read in this posting of yours. And I am not >trying to judge you harshly because your English may not be perfect. > >>The elo system does not use all the information to get the best estimate for the >>elo. > >Yes it does, emphatically, and scientifically (meaning objectively, without >subjectivity; meaning unbiased). > >> >>It is using only results and not the games. > >Right, since an ELO rating is all about predicting the relative results of a >player versus other rated players. The point is that analyzing the games may help in predicting the future results. I said 'results', meaning % of available >points scored by the player--i.e. (Wins + 0.5 * Draws)/(Total Games Rated). >What good is a rating system, if it doesn't predict *results*. > >An ELO rating is designed (that is its mathematical nature, its intended >function) to predict results *of a series of games* against opponents of known >ELO rating, not how well a player (or computer) will do in a particular postion, >whether opening, middlegame, endgame, whether closed or open, whether when kings >castled on the same side or kings castled on opposite sides or with one or both >kings uncastled. I know the purpose of the rating system is to predict results but they assume a simple model. The model say that the ability of a player in a game has a normal distribution with standard deviation of 200(there is a linear formula for calculating the rating that gives almost the same result and I know that this formula is used in Israel for calculating the rating system). This model is wrong and does not use the results of the games correctly to get the best estimate. I can give a simple example suppose player A is unstable player and play like a player with rating 2500 in 50% of the games and like a player with rating 2000 in 50% of the games. If A plays against strong players with rating 2500 A's score will be at least 25% and A's rating will be higher relative to the case that A plays against weak players. If I know it from games and A choose to play most of the games against strong players than A's rating will be higher than the rating that A deserves based on playing against all players. > >This bears repeating--an ELO rating does not even attempt to determine how well >a rated player (even if a computer) will do in various phases of the game, or in >various types of postions. All those details are subsumed in the strength >assigned to the player based on the bottom line--results: Win, Draw or >Loss--against rated opponents. Against multiple rated opponents, not just one >opponent, since an ELO rating is a relative measure of one player's strength >versus many other players in the same rating pool, versus the average strength >of the pool on the whole. > >Analyzing in detail the playing styles and skills, contrasting two different >players (human or computer), assigning personal rating numbers to programs based >on their hodge-podge (mix) of skills and abilities across many positions, is all >well and good. But that is not what the ELO system is designed to do. That is >a personal system one may devise (for perfectly valid reasons)--but not *the ELO >sytem* of Dr. Arpad Elo. > >> >>I am sure that it is possible to do a calculating rating program that will give >>better estimate for the rating by not only counting the results but also by >>analyzing the games and evaluation of programs. > >The ELO system is not designed to predict perfectly a single game, or even the >results of playing a single opponent (for example, A versus B only). It is >designed to predict the %score expected when A plays B, C, D, E, F, G, etc, of >with known ELO ratings and ELO rating average. I know and I believe that it is possible to predict better the results of A against B,C,D... if you also analyze the games. > >Because the ELO system presupposes natural variability, it doesn't guarantee any >particular score, against any particular individual (nor against any particular >field of opponents). > >The ELO system doesn't only predict results. It handles the adjustment of the >player's rating, according to recent *results*. > >It adjusts an ELO rating up, when the % of points scored is higher than that >predicted by the relative ELO ratings of the player and each of his opponents. >It adjusts an ELO rating down, when the % of points scored is lower than >predicted by the relative ELO ratings of the player and each of his oponents. > >> >>It is not simple to do this program and I am not going to do it but it is >>possible. >> >> >>Here is one example when you can learn from analyzing games things that you >>cannnot learn from watching results without games: > >I agree you can learn things from watching the details (move choices) of a >game--about both players. > >> >>Suppose you see that in one game program A outsearched program B and got >>advantage by the evaluation of both programs. >> >>The evaluation of both programs was wrong and program A lost because the >>position that both programs evaluated as clear advantage for A was really a >>losing position for A. >> >>If you analyze the game you can understand it and increase A's rating based on >>this game. > >Uri, if the positional skills of program B outweigh (normally) the increased >search capability of program A, then it is possible that program B is stronger >than program A. By stronger, I mean that B will achieve better results than A, >in a head to head competition. > >Perhaps A outsearches B only on rare occasions (even in several observed games >in a row). Or A oursearches B (as in your own given example) but A doesn't win >the game (as in your example). How can you conclude A is better (based on >deeper search) when the *results* of that search didn't obtain a victory. I can see in the game that both programs did not understand the position so better positional understanding was not relevant in the game. I am talking about a case that program A went to a lost position because it outsearched the opponent. if program A won a rook by outsearching the opponent and did not see that B has a mate attack and the evaluation of B also discovers that B did not understand that it has a mate attack then there was no superior positional understanding of B. Uri
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