36
The answer by MikroDel gives the commonly-used "Reinfeld values" of pawn=1, bishop=knight=3, rook=5, and queen=9 (kings are essentially worth an infinite number of points, because the game ends if it is lost). While this is a good guide, chess is rarely that simple. Many books will give the value of bishops as 3.5 instead of 3, simply because they are often ...
33
Why do chess engines fail to spot good moves in some positions?
The reason are called forward pruning techniques (see http://chessprogramming.wikispaces.com/Pruning)
with ProbCut in first line.
The move 15...Bf2 is pruned on shallow deeps because it includes the sacrifice 16.Rxf1 without regaining something concrete with evidence immediately after.
The ...
22
It's because 1. exf8=Q+ Kxh7 2. Rxd7?? would be stalemate. I think it is a even a theoretical draw after 1. exf8=Q+ Kxh7 2. Qg7+. Therefore 1. exf8=B+! (with check!) is better, since white then can keep an extra piece and win easily.
[FEN "5r2/3qPbkB/8/7P/8/8/8/1K1R4 w - - 0 1"]
1. exf8=Q+ (1. exf8=B+!) Kxh7 2. Rxd7? (2. Qg7+)
20
There is a very easy way to detect whether King and Pawn endgames are drawn or not.
This method I use is a very easy to understand one from Karsten Mueller and Frank Lamprecht's excellent book Secrets of Pawn Endings
It concerns key squares and opposition
The rule states that if pawn has not reached or crossed the central line (5th rank for White and 4th ...
17
Pawn - 1 point
Bishop, Knight - 3 Pawns
Rook - 5 Pawns
Queen - 9 Pawns
The evaluation depends on the position.
In some situation you will find it equal or good to give you Rook and Pawn (6 Pawns) for Bishop and Knight (6 Pawns). But it is also possible that two light pieces are more valuable than Rook + Pawn.
The value of pieces given to you will be a ...
17
Those aren't scores; there are just three possible scores in chess: White wins, Black wins, and draw.
Those are evaluations of the chess engine; a score of +0.62 means the engine thinks White's position is better by 0.62 pawns. A negative score would mean Black is better. On professional level, a score of 1.5 pawns is in most positions decisive, i.e. enough ...
16
The Site ratings at slow time controls can be quite reliable for servers where strong players congregate (ICC, FICS to name a few) as the ratings VERY closely reflect your true playing strength if you've played enough games. For very standardized rating systems such as USCF and FIDE/ELO, you will notice that the different rating classes tend to point to the ...
14
As long as chess can't be calculated from beginning to end, it is very hard to scientifically prove an opening to be refuted (aside from lines that leave you with such hopeless situations like a bare king against king and rook, of course).
If you are satisfied with a less scientific proof, I'd say gambits are even less so refuted. In my opinion, nearly all ...
14
Different engines have different "scales" for their numerical evaluations. For instance, in a typical middlegame position with plenty of play left, when Houdini says +2.00 or better, it is highly probable that White has a winning advantage (though even here I've included qualifications for a reason). But consider: one could modify the source code of Houdini ...
14
The best way to normalise a centipawn score to [-1,+1] range is using a sigmoid function, as that closely approximates the likelihood of a given centipawn advantage converting to a win, and avoids the need to identify a strict maximum or minimum. This is discussed here.
13
There's a great analysis/article about this by GM Larry Kaufman available here.
To summarize:
Pawn = 1
Knight = Bishop = 3.25
Bishop Pair = 0.5
Rook = 5
Queen = 9.75
There's also a lot more detail in the article about what situations favor which groups of pieces. For example, when B+N is better than R+P, or when Q+P is better than R+R, etc.
13
Individual pieces:
Pawn - 1 point
Knight - 3 points
Bishop - 3 points
Rook - 5 points
Queen - 9 points
Piece combinations:
Rook and Knight - 7.5 points
Rook and Bishop - 8 points
Pair of Rooks - 10 points
Three minor pieces - 10 points
Rook and two minor pieces - 11 points
12
I am trying this with Houdini 1.5 (the free version). At first 15...Bf2 doesn't show up in the top 5 moves, then when it reaches depth 15, it does, as #1. Takes about 19 seconds on my four year old computer, not that long.
So it doesn't fail to spot it, instead it only considers it the best move once depth 15 is reached. Apparently, as long as it only looks ...
12
A good chess engine won't stop after a predetermined number of moves, but will keep looking until the position is "quiescent", which roughly speaking means that there are no pending captures or checks. See Quiescence Search in chessprogramming wikispaces for a more detailed explanation.
10
Many gambits are unsound. The proof is told by the number of these played at the highest levels of the game. So, if you don't see the Blackmar-Diemer gambit at top tournaments, you can assume that its disadvantages outweigh its advantages. The King's Gambit is one famously busted opening.
That being said, we're not top players. Most of us can't beat the ...
9
Here's a good starting point. Material comparison is key (and easy), then you can tune that to consider positional aspects like open ranks/files/diagonals, pawn structure, etc.
https://www.chessprogramming.org/Evaluation
9
A gambit can be proven to be unsound by using a modern chess engine. Having said this, I would like to mention a comic gambit, known as the Fred defense:
[FEN ""]
1.e4 f5 2.exf5 Kf7 3.Qh5+ g6 4.fxg6+ Kg7 5.gxh7 Rxh7 6.Qg4+ Kh8
White has picked up 2 pawns. In return, the black king has done an artificial castle and black's pieces are ready to develop and ...
9
Black is down material but still has some strength. The most obvious one is that he has a pawn majority on the queenside, meaning potentially passed pawn if he manages to push his majority. So Black's plan will be to put both rooks behind the pawns and go for ...a5-a4, ...b5-b4 etc...
In a very simple way White can fight against Black play (it's prophylaxie)...
9
As pointed out by Glorfindel, these are evaluations, which tell you who the engine thinks is better. A positive score means white is better, a negative black is better and values around zero mean that both sides are equal. These evaluation values are (traditionally) displayed with two decimals which is much too high precision for humans. In practical play ...
9
If I understand correctly your x axis is the moves. Your script implied Anand and Prag were blundering every time they make a move,
Clearly you have a bug in your script. Stockfish engine always give you a score relative to the player making the move, NOT white. You need to multiply the score by minus one if it’s Black to move.
Please do this and you will ...
8
Though one cannot trade one's king for other considerations -- and in this sense the king cannot be evaluated -- the king still has a practical strength as an attacking and defending piece in the many concrete positions in which no immediate mate is in view -- especially during the endgame. This strength can indeed be evaluated. World Champion Emanuel ...
8
I think this picture describes the situation quite well. It was created from 400k games, and considers only plain piece material.
Source: Pawn Advantage, Win Percentage, and ELO
8
There are a couple of things here.
First, each program is going to have its own way of evaluating positions so the scores can't be directly compared. For example, I was running StockFish against Rybka recently and found Stockfish's scores were about double those of Rybka. I was surprised by this, but it's pretty clear that a score of 1 doesn't always mean ...
7
Perhaps show them positions and ask them to assess them and analyze the various salient features (i.e., king safety, piece mobility, central control, weak squares/color complexes, etc.). Naturally, novice players likely won't be able to formulate a cogent response, but if you're looking to identify at least reasonably strong/experienced players, then I would ...
7
The standard is usually to compare pieces to each other (i.e how many pawns is a knight worth, a bishop, a queen etc.?
Another way is to determine piece value dynamically using the idea of "absolute/potential activity" and "nominal activity". This idea is based on the number of squares any given piece controls (and I believe is partly how computer engines ...
7
1) Unwarranted resignations happen on occasion even in tournament play, sometimes even in a won position. If your student does this in an instructional game, it's a teachable moment. In the present game, you might learn too: saying
"haha, now I get a free rook" during the game is distracting the opponent,
which is against the rules whether or not you in ...
7
I looked at my library, and opened up a number of books. The old Dvoretsky books really do not do this much, but the "School of Future Champions" and "School of Chess Excellence" series do have many sections that just say "white (or black) to play", and nothing more.
Other Dvoretsky books that do that significantly are "Recognizing Your Opponent's Resources"...
6
For a very accurate rank of a player's quality, you can use the excellent tool provided by www.chess-db.com. It lets you upload your games and after some minutes it outputs the quality of both players in percentage compared with the best moves of a strong engine.
This is the page to upload a PGN file:
http://chess-db.com/public/game_upload.jsp
And this is ...
6
Black has an overwhelming advantage and should win easily. Being up by a whole piece is a huge advantage that basically can't be overcome by purely positional considerations.
The most straightforward way for Black to win is to try to trade pieces and end up in an endgame where he has one piece to White's zero; a win at that point would be trivial.
He could ...
6
On the website of Houdini, one of the best chess engines (see for instance CCRL or CEGT), the author writes
Houdini 4 uses calibrated evaluations in which engine scores correlate directly with the win expectancy in the position. A +1.00 pawn advantage gives a 80% chance of winning the game against an equal opponent at blitz time control. At +2.00 the ...
Only top voted, non community-wiki answers of a minimum length are eligible
