The rating system for endgames is similar to that used in the tactic problems, the Glicko rating system is used to
rate both endgame problems and players. For failed attempts rating adjustments are done based on a straightforward
0-1 result. Your rating adjustment for successful rating attempts depends on how many
optimal moves you played before completing the problem.
For practice mode, successful rating adjustments are based on how much longer your number of moves was than the
fastest number of moves. If you play the optimal move at each point then you will receive a full 1-0
result. However
Theory mode rating adjustments for successful attempts are similar to practice mode, except that instead of
total moves played impacting the outcome, it is the extra moves that would have been used if the longer moves
had been allowed. For positions where you attempt to play more than one sub-optimal move, the move with the
longest length to mate is used for rating purposes.
Note
The endgame training tool currently uses the shortest distance to mate as the measurement of best moves. This
means that to make perfect play, all your moves must lead to the quickest mate. This can sometimes lead to
situations where the most obvious move (for example promoting or taking an opponent's piece) may not always be
the quickest way to mate. In these situations the server will treat takes or promotions as equivalent to the
shortest mating move (as long as capture or promotion doesn't extend the length of the shortest mate by more
than 2 moves). In addition, moves that might not immediately take a piece or promote, but may lead to a take or
promotion on the next move will also be allowed as long as the total sequence doesn't increase the moves to win
by more than 3 moves. In the future, distance to conversion endgame tables will also be used, and this will
allow a larger set of these "not shortest but still practical moves" to be allowed.
Note
No matter how sub-optimal your solution, or how many times you use the "Play Best" button, you will never lose
more points that you would if the problem is marked wrong.
Note
The result notification for correct endgames has two extra lines. The first line shows the number of moves, and
then in brackets the number of extra moves. The second line shows you the score you received, 50% means you
received a result equivalent to a draw, i.e. 0.5-0.5, 25% means you received closer to a loss (or 0.25-0.75),
and 100% means you received maximum points (i.e. the equivalent of a 1-0 result). After the percentage score,
the actual number of moves you were punished for is also shown. Where you played sub-optimal , but allowed
moves such as slightly longer moves that promoted or took a piece, this value may be smaller than the total
number of sub-optimal moves shown on the number of moves line.
