Fixing RP Score 2011
In February 2011 we added achievements to Stendhal in order to encourage players to have a far richer playing experience than just killing monsters. This has really worked out great with - at the time of writing - over 12000 achievements granted. Feedback from players has been very positive and many players have discovered aspects of Stendhal that they did not pay attention to in the past.
In March we improved the hall of fame to take the achievement score into account for the best player calculation. After some initial struggling because it caused some players to temporary drop out of the top 10, this did work fine, too. But here we introduced a bug. The ranking itself is fine (except for rounding errors), but the score is not.
What's wrong and why?
- What's wrong with the RP score?
- The RP score graph has an exponential growth, just like the XP requirement per level. But unlike level, it is missing a logarithm operation in the calculation.
- Why is that bad?
- It means that weak players don't have a chance to get RP points.
- The average level of someone having an RP score above 0 is 150.
- One third of all players is below level 10, two thirds are below level 50, so they don't have an RP score.
- The numbers get really big at the upper end of the hall of fame
- Rounding errors in the ranking start at rank 150 because lots of people have the exact same very low score. Below 270 it is mostly random.
- What is good?
- The ranking itself (above the rounding error boundary where lots of people have the exact same score) is accurate
- Wait, logarithms are really difficult, don't they totally screw up scale?
- Actually, in most cases the logarithm is a very natural thing: It's often used by biologists to describe grows of plants and animals. Applying logarithm to XP points has a very long tradition in role playing games. Of course, calling it "level" instead of "logarithm of xp" makes it a lot less scary.
What will happen after the fix?
- How are high level players affected?
- The ranking will not change
- The numbers will get smaller and the gap in the scores between ranks will get smaller
- The difficulty will not change despite the gap being smaller. Think of this change as saying level 298.0 and 299.0 instead of xp 262,426,800 and 265,085,000. Yes, the gap between 298.0 and 299.0 looks small, but it is the same as the gap between those xp numbers. (The RP score will be higher than the 3 digit level numbers because we will shift the decimal point to the right).
- How are mid level players affected?
- The range of points will get larger
- The ranking will get more accurate because there will be no more rounding error with lots of people having the exact same score.
- How are low level player affected?
- You will now be able to get points.
- An old score of 0 means something between 0 and 6213 now; an old score of 1 means something between 6214 and 7304 now
- Ranking below 270 will work.
All numbers are based on stendhalgame.org 2011-06-05.
Other ideas and concerns