I’ve thought of a problem with the “take the prizes from the bottom” algorithm for dealing with unrated prize restrictions. It works for the simple examples given earlier, but consider this one:
$$ 1200-600-300-100-100. Unrated can’t win more than $500.
Assume the top five players are A, B, C, D, and E, and A is unrated. The “take prizes from the bottom” algorithm produces this result:
A: $500 B: $1200: C: $600
We announced five prizes but we only awarded three. This can’t be right.
Instead I’d like to propose the following algorithm, which also allows for multiple unrated players and class prizes. Unfortunately it’s fairly complicated. It’s pretty much what I’ve been doing in all the tournaments that I’ve directed, but until now I hadn’t considered some of the more obscure cases.
Step 1: Calculate the prizes as if the unrated players weren’t in the tournament. This establishes the maximum prize for each rated player. In practice these prizes don’t have to calculated until they’re needed in step 2E.
Step 1A: If unrated players are limited to a percentage of prizes won, calculate the prizes as if all players were rated and then multiply the prize of each unrated player by the percentage. This establishes the maximum prize for each unrated player. Again, these prizes don’t need to be calculated until they’re needed in step 2D.
Step 2: For each score group starting with the highest one, until all unrated players have been awarded prizes and there is no more excess prize money:
Step 2A: Pull one prize for each tied player into the prize pool (or pull in a single prize if there is only one player in the score group).
Step 2B: Add in any excess prize money from the next higher score group.
Step 2C: Divide the prize pool equally among the tied players.
Step 2D: Apply prize restrictions for unrated players. If prizes are reduced take the unrated players out of the prize pool and go back to step 2C.
Step 2E: Apply prize restrictions for rated players. This may result in excess prize money which will go to the next lower score group.
Step 2F: If any players in the score group would win more money by taking a class prize, remove them from the prize pool and go back to step 2C.
Step 2G: Award prizes to any players left in the prize pool, and proceed to the next score group (step 2).
Step 3: If there is excess prize money after all prizes have been awarded, create a new prize and divide it among players in the next score group (step 2).
Step 4: Once prizes have been awarded to all unrated players and there is no more excess prize money, award the remaining prizes normally.
How does this work in practice? Let’s look at the example which I gave earlier:
$$ 1200-600-300-100-100. Unrated can’t win more than $500.
Assume the top five players are A, B, C, D, and E, and A is unrated.
I’ll show just the steps which are relevant.
Step 1: prize limits for rated players
B: $1200 C: $600 D: $300 E: $100 (F etc.: $100 - won’t be needed)
Step 2: top score group
Step 2A: $1200, only A is in the score group
Step 2D: A is unrated so he’s limited to $500. Excess is $700.
Step 2: second score group
Step 2A: $600, only B is in the score group
Step 2B: Add the $700 excess increases the prize to $1300
Step 2E: B’s maximum prize (step 1) is $1200. Excess is $100.
Step 2: third score group
Step 2A: $300, only C is in the score group
Step 2B: Add the $700 excess increases the prize to $400.
Step 2E: C’s maximum prize is $600, so he can win the entire $400.
Step 4: since there are no more unrated players and no more excess prize money, award the remaining prizes normally: D $100, E $100.
The result is:
A: $500 B: $1200 C: $400 D: $100 E: $100
Can anyone think of prize structure where this algorithm wouldn’t work?
Bob Messenger