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Chess Engines' Evaluations

  • WGM Natalia_Pogonina
  • | Jan 25, 2012
  • | 27544 views
  • | 56 comments

Nowadays powerful chess engines have become routine assistants of competitive chess players. Both amateurs and professionals use them to analyze their games, prepare opening lines, evaluate certain positions, etc. Most websites that broadcast games also offer a built-in engine evaluation to make the viewing process more interesting for chess fans. Such mighty servants as chess engines are of great use, but they also pose a serious danger.

First of all, it’s very easy to lose one’s own tactical skill if one starts following the computer lines without thinking for oneself. Secondly, quite a few players, even very strong ones, start “worshipping” engines and religiously trusting them. However, there are still blank spots in the evaluation mechanisms of the programs, so even at a large depth the first line of a program is not necessarily the best move.  Also, when playing humans we have to try to pose as much difficulties before the opponent as possible, place them under psychological pressure. Meanwhile, computers don’t know such things, and for them a king vs king position is evaluated the same as an insanely complicated draw that can be reached by making 20 one-and-only moves in a row.

Computer engines evaluate positions and offer an aggregate figure to show who is ahead. The number means how much better one side is in terms of material. Of course, in most positions material is not the only factor to consider, so the figure is derived by carefully weighing the tactical variations and positional factors.

Equality: =, from 0 to 0.26

Small advantage for White: +/=, over 0.27 and up to 0.7

Serious advantage for White: +/- over 0.7

Decisive advantage for White: +-, over 1.5

The signs for Black are similar (=, =/+, -/+, -+). A – sign is used to show that Black is ahead. E.g. a -0.8 evaluation means that Black has a serious advantage that is equal to about 0.8 of a pawn.

In some theoretically drawn positions the engines might still be saying that one side is ahead. Therefore, in endgames one should be especially careful when analyzing. The only exception is the endgame (Nalimov) tablebases (6-men are available online; 7-men are harder to find; creation of 32-men would mean that chess is solved). Using those one can instantly find the mathematical evaluation of the position: draw or a win for one of the sides.

Here is an example from the recently played Karjakin vs Topalov game, round 7 of Tata Steel Chess tournament:

The strong sides of chess engines are calculation and defense. They can also come up with unexpected and bizarre-looking ideas in certain positions. The weaknesses (if we can say so about players rated well over 3000) are positional evaluation and long-term planning. Quite often a chess engine would be saying that one side is better for a series of moves, and then all of a sudden treacherously change the evaluation for the opposite.

I use chess engines to check all my games and openings. However, the final decision belongs to me. This is especially true for positions with a few more or less equal options available. In such cases it’s very important to understand the idea/plan behind each of the moves. The difference might become obvious only a couple of moves later. In such situations chess engines are of no use, so you should either rely on your own brain, or check out leading players’ games to make a choice. Don’t be afraid to make a move that is not deemed to be the best by the engine.

sm_2011_1_kolo_analyzy_12.jpg

Post-mortem: Robert Huebner and Natalia Pogonina. Photo by Martin Chrz

The instructive example of the above-mentioned principles will be my first game against former world #3 Robert Huebner from the Snowdrops vs Oldhands match (the second game was drawn as well). Most of the time the engine I have been using to analyze was claiming that the position is equal. However, by doing so it was neglecting some important features of the position. For example, after 20…dc the computer still says the evaluation is close to 0, but a qualified human would tell you that White is better. Black is obliged to defend passively, while White has some plans associated with pushing the kingside pawns. Therefore, in human terms it’s a “position for two results”: either White will win, or the game will be drawn. Maybe with strong play the position is indeed drawish, but Black is the only side at risk.

Therefore, if you prepare for the game only by memorizing chess engines’ moves and evaluations, at some point you will get in trouble. Always try to understand the ideas behind moves and make sure you understand why the position is evaluated as it is. For us, humans, intuition and experience are more important than brute force calculation. A chess engine is a great assistant, but it can never substitute for using one’s own brain in an over-the-board game.

Comments


  • 18 months ago

    WGM Natalia_Pogonina

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  • 18 months ago

    carlafierro7

    The best results i get are to play the positions i am interested in against 8 chess computer players in a double round robin, blitz 1 minute + 17 seconds. The chess players have to be 4 strong, 2 medium and 2 weak. Now, by going through the games, and tweaking the starting position (i.e. how about this, or how about that) ... i get a good idea as to what the basics tactics, strategy and endgames to come out. For example, i have totally refuted, the Latvian, Elephant and other silly gambits. By refuted, i mean reduced them to mate-in-X (usually about mate in 37 from most ECO positions)

  • 3 years ago

    jbirchley

    Thanks Natalia, what you write makes a lot of sense and we should always keep those points in mind when we use the engines. Particularly good is what you say about draw evaluations - a game might be saved as a draw only if the defending players makes the one right move 10 times in a row, but that could be very tough for any human player to find.

  • 3 years ago

    Knights-Occulus

    Nice article :-)

  • 3 years ago

    MaxxLange

    An interesting point is that, in some positions, engines will evaluate as roughly equal, due to their ability to find long sequences of forced defensive moves. These moves may be very very difficult for a human player to find! In this kind of situation, I'd consider one side of an "equal" position to actually have a large practical advantage.

  • 3 years ago

    diogens

    Smile

    Who said something like? "universe and human stupidity are infinite, yet from the former, I'm not completely sure"

  • 3 years ago

    satorichess

     Natalia,

    we know you are a great chess champion, I'm sure I can interpret the thoughts of us all to thank you once again for your work . It 's always a great honor to be able to compare our views with a great champion and again we are all very grateful to you dear Natalia. 

  • 3 years ago

    Shippen

    Hi Natalia, I have noticed that  often when I make a blunder the opponent makes one straight back and vice versa. Is it because your brain is following a pattern and when the pattern is broken you can be confused. 

  • 3 years ago

    Twobit

    Thanks Natalia. I do hear the criticism about using computers that they beat you to pulp (unless you dumb them down), and you never learn anything. But then there is the counterargument that you should always play against perfection to learn to avoid huge blunders, because the computer is unforgiving and you can not get away when your opponent makes a "counter blunder".  

  • 3 years ago

    WGM Natalia_Pogonina

    @ Twobit I use Houdini most of the time. Regarding engines for amateurs and pros: it depends on the goals. For pros it's about improving and winning. For many amateurs the interface and gaming experience matters a lot. Therefore, many people wold prefer, let's say, ChessMaster to Rybka. Anyway, even a "casual" engine will probably be at least 2800+, so it's perfectly fine for a chess fan.

    As to the "free fall" concept: a lot depends on whom we call amateurs - non-competitive players, club players, masters, GMs who have a job besides chess? Many games are indeed decided by a single serious blunder, but there are also many cases when both sides blunder, and the outcome is unpredictable.

    Now to the people who have been arguing with DaethFromAfar: please don't feed the troll. That person is illiterate, rude (to the point of using cuss words repetitively), and obviously has no expertise whatsoever in either chess or IT. Just dont' waste your time. Smile

  • 3 years ago

    UnratedGamesOnly

    Excellent article!, and hopefully it will shed some light on how chess engines should be used as a teaching tool, not as if they give chess site.  If i hear one more kid at a tournament talk about how "Fritz said i was winning" But ask that kid why he was winning and you get a blank stare. 

  • 3 years ago

    satorichess

    ha,ha,ha, great,

    have a nice day :-)

  • 3 years ago

    Twobit

    Ok, I may not be able to cook a Russian dinner, but I have feelings, too!

  • 3 years ago

    satorichess

    you are perfectly right @twobit, and that's why (cheating or not) this challenge are quite useless today. A machine don't have emotion but if you are playing  even with GM Natalia and she makes a blunder at some point of the game the psychological effect could be devastating.....and if you are able maybe you can take advantage and maybe win.And maybe she will invite you for a russian dinner you see???? This is far more interesting to me than playing with any wonderful machine you may have :-)

  • 3 years ago

    Twobit

    Regarding the Deep Blue game Kasparov said he played specifically anti-computer moves. His accusation about the Deep Blue Team cheating was that in game 2 the computer played a very un-computer-like move(s) (implying human interference), should my aging memory not fail me. So, when a human plays a computer (and he knows it, too), he may play totally differently than facing a human opponent, whose weaknesses he may be already familiar with.

  • 3 years ago

    satorichess

    Agree with GM Natalia who she's always clear and effective on her teachings.

    I like to add that chess it's great to be played against human for the psychological implications this has (which are a great part of the game). So just don't worship too much computer here guys they are great (sometimes) analysis tools as Natalia showed but that's all. after the initial interest and the surprise of the 90's we start again, perhaps to give proper value to the machines and men now ..........even the fastest runner in the world it's not interested in competing with a motorbike, what could be  the point at the end? The challenge must always be between humans/humans or machines/machines and  I know that there are several tournaments in the world of the best chess engine already. Bobby Fischer one of the all time greatest player in the world has always refused categorically to confront with a machine and surely shared many of the opinions expressed by Natalia on her article. On the other side Kasparov did it (and despite some losses) and very well, but have you ever looked at his game against Deep Blue or Fritz? Not very interesting chess really in most cases.

     




  • 3 years ago

    WellRounded

    Obviously this is the modern classic argument amongst chess players, but I think anyone who believes engines will never play like humans are kidding themselves.  Of course computers will be able to curb their play into a more humanistic style of play, even if it means playing a second best option; i.e., A future chess engine may have two options: optimal play, and humanistic play, where the latter is still significantly more powerful than any human player.  What the engines are capable of doing is entirely up to their programmers and their hardware. 

  • 3 years ago

    Vease

    If Houdini and Rybka always find the 'best' move how come they can take games off each other in matches? That means one of them must have missed something, or even, heaven forbid, misjudged a position!

    The German guy who was caught cheating using an engine in a tournament gave the game away by telling one of his opponent (a strong GM) that the final position was mate in 8 when the GM couldn't see it. When people went over his other games they saw blatant 'computer' moves where the guy had a crushing position but played some random looking move when there was a simple win on the board. Obviously the weird looking move was considered 'better' by the engine, but a human would always play the obvious winning continuation.

    When I use an engine to analyse my games it often throws up 'better' moves than what I played, but I don't understand them. In this case I just say 'I would never have found that' and go down the move list until I see a move or variation i do understand and treat that as the improvement if its better than the move I played.

  • 3 years ago

    suzettemy

    Chess is alive and well for me; Thank you Natalia!

  • 3 years ago

    Twobit

    Thanks for the article. First, I am so disappointed that Rybka fell from grace. Second, I read somewhere that now they are allowing the use of chess engines in postal chess. That should say a lot about their practical value. Third is a question, which engine do you use and is there a difference in between engines recommended for amateurs or pros? Ok, that was two questions. Last, I like the way de la Maza was using engine evaluation to point out that most of us patzers can chug along for awhile until making one huge blunder, then the rest is just free fall.

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