Sudoku Statistics

Sudoku statistics are now recorded for all registered users. When you complete a puzzle that is eligible to be scored, the program shows your average score, highest score and your Rank Index. This index is the average of the last 12 scores, excluding the highest and the lowest.

Sudoku Scoring System

A new scoring system has now been introduced for Sudoku puzzles. The motivation behind this is to try introduce a uniform performance metric across all puzzles, including those entered manually from other sources. This will be used to provide player rankings and statistics in the future.

Currently, the only measure of performance is your time and a grading of puzzles across four levels. A new rating index is now calculated for all puzzles, roughly ranging between 900 to 1600. This attempts to provide a much finer-grained indicator of puzzle difficulty although, as you well appreciate, this is not an exact science.

The actual score is calculated when you complete the puzzle according to the following formula:

Score = Rating + TimeBonus - Accuracy - SolveAids

where:

• Rating = the rating index assigned to each puzzle. This index attempts to measure the difficulty of the puzzle by examining at each stage of the solving process how many cells can be solved by logic relative to the number of unsolved cells. It also looks at what techniques are required to solve those cells. Those that rely on more sophisticated techniques greatly increase the rating index. The current difficulty level (Easy, Medium, Hard, Tough) is only based on the techniques required to solve and you may now find that some Easy puzzles have a higher rating than other Medium ones or similarly for Medium/Hard/Tough.
  
• TimeBonus = extra points for completing the puzzle quickly. In fact, time is still the most important factor determining your score. The time bonus is computed by taking the average time per difficulty level divided by your time and then multiplied by the rating index. For example, the average time for Medium puzzles is currently set at 12 minutes (720 seconds) so if you complete a puzzle with a rating of 1100 in 6 minutes, you will score a time bonus of (720/360 * 1100), ie 2200 which is twice the rating for that puzzle. If you completed the puzzle in 20 minutes (1200 seconds), your time bonus would be (720/1200 * 1100) ie 660.
  
• Accuracy = the number of errors you make. For the first cell that you enter an incorrect value, you lose 30 points, for each subsequent error the points lost increases by 10. So you would lose 40 points for the second error and so on. Note that pencil marks do not affect the scoring in any way.
  
• SolveAids = each time you use a hint or clue or check your input. You lose 40 points for each hint, 50 for each clue and 20 each time you check your input.
  

The parameters of the formula will most likely be refined based on empirical data collected as well as user feedback. Please feel free to comment here.