The evaluation graph shows how the engine’s evaluation changed from the first move of a game to the last. It tells you who stood better and after which move the game was decided, even in a game you have never seen. It is a good place to start a review, because it points to the moves worth your time.
What the curve shows
The engine evaluates the position after every move, and the graph joins those evaluations into one line. The first move is on the left, the last on the right. The vertical axis is the evaluation in pawns.
The middle of the graph is equality. Above it White is better, below it Black. A point at +1.0 means the engine puts White ahead by about a pawn; -2.5 means Black is ahead by two and a half. On chess.rodeo the graph is flipped together with the board: when the board is shown from Black’s side, Black’s advantage is at the top.
The pawns are a unit of measure. The evaluation takes in material, king safety, piece activity and pawn structure, so the line can rise when nothing has been captured: a knight reaches a strong square, for example, or the opponent’s king loses its cover. The numbers themselves are explained in what the evaluation number means, and how the engine arrives at them in how Stockfish evaluates positions.
Flat line, slope and jump
There are three kinds of stretch on a graph.
- A flat line. Both players are making moves close to the best ones, and the evaluation stays where it is. There is usually nothing to review here.
- A gentle slope. The evaluation drifts one way a little at a time. This is what converting an advantage looks like, or several small inaccuracies in a row.
- A jump. In one move the line goes sharply up or down. That move changed the evaluation more than its neighbors did, so start your review with it.
How to find the turning point
A game that somebody won usually has a move after which the evaluation changed sharply. Here is an example from the Sicilian Defense: eight moves have been played, and White is slightly better.
On the graph the first position sits on a flat stretch, and the second at the bottom of a drop. After Qxd6?? the bishop on e7 takes the queen, and White has nothing to recapture with on d6. The evaluation falls from about +0.3 to about -6: White has given a queen for a pawn. You do not have to go through the moves to find this mistake, because on the graph it shows as a drop.
The biggest jumps fall on the moves that decided the game. Click or tap the graph where a jump begins, and the board shows the position before the mistake. What such mistakes look like over the board is covered in common chess mistakes.
Mate and the edges of the graph
An ordinary evaluation is a number like +1.4 or -0.7. When the engine finds a forced mate, it stops counting pawns and shows the number of moves to mate. On chess.rodeo that is written M5, mate in five moves; elsewhere you will also see #5.
A forced mate is drawn at the very edge of the graph: the top edge when White is mating, the bottom when Black is. An extra piece or an extra rook does not reach the edge.
The difference matters in a review. With an evaluation of M5 all that is left is to play out the forced line, while at +6 the game still has to be won. If the line ran high for a long time and then fell to the middle, a won position was let slip. That is another place to review early.
How to review a game with the graph
There is no need to replay the whole game move by move. Start with the jumps:
- Find the two or three biggest jumps on the graph.
- Click or tap the graph right before each of them to open the position.
- Work out what you missed, and compare your move with the engine’s best move.
- Note who made the mistake: you or your opponent.
A game is usually decided by a few moves. The graph shows them at once, and the quiet stretches can be skimmed.
Accuracy as a percentage rates the game as a whole, and the graph shows on which moves that accuracy was lost. A review from start to finish is described in how to analyze chess games.
On chess.rodeo every analyzed game has an evaluation graph, for free. Click or tap anywhere on the graph and the board goes to that move. Next to the board you will see the move’s label (Book, Best, Mistake, Blunder and others), the evaluation before and after the move, and the engine’s best move. Brilliant moves, mistakes, misses and blunders are marked on the line with colored dots. A single position can be analyzed on the analysis board.