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2 IronAxe. I suggest simplifying the situation for the start.
1. Let's forget about the oscillator for now and use a purely nonlinear coefficient for calculating the rating (Example #1). We will also consider it from 0 to 100 - no concessions for underdogs. We only round down to the nearest whole number, with a minimum rating of 1, i.e., we don't set zero...
2. Now, let's calculate the tournament rating based on the average rating of the top five players. For the first tournament, the rating will be 1 (because the ratings of all participants are currently equal). Then, we will recalculate it based on the results of the first tournament.
3. Let the first tournament be the recently held BB. We need statistics. It doesn't matter that this tournament