How is rating computed in case of ties?

@admin: I am wondering how the rating for long contests is computed in case of ties. Specifically, I am interested in the case of the recently ended May 2014 long contest, where me and @aawisong where tied on the first place.

I know that in the rating formula there is a (weighted) component equal to the number of contestants / rank. Since there were about 5000 contestants and my rank and @aawisong’s rank were 1, I would have expected our rating to increase by something between 4000-5000 points (or more for @aawisong, since his rating before the contest was lower).

However, my rating increased only by about 3100 points, while @aawisong’s rating increased by about 3700 points (it is normal for his rating increase to be higher, since he started from a lower rating than me before the contest). These values suggest to me that the value of the rank considered for both of us in the rating formula was not 1, but probably something between 1 and 2. Is this correct? If it is, can I know what rank is considered for each user in the rating formula in case of ties ? (e.g. if there are 10 people with equal scores on the 1st place, will rank 1 be considered for each of them or some other value larger than 1 ?)

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We follow score based rating and hence we have fractional ranking system which is used for calculating the final rating of the user at the end of any rated contest.

Please refer this link for the same. 1.5 was used as rank for both of you while calculating your rating. (10 people with equal scores on the 1st place will be ranked as 5.5.)

Also, the weighted component (bonus) in our rating is found by m * sqrt ( avg participation * number of contestants)/rank (which is equal for both of you).

Since sqrt (avg participation * number of contestants) is always going to be less than the number of contestants, the bonus was not as much as you expected it to be. The variable avg participation considers all the contests in the category (i.e, all long challenges till MAY14) for which the ratings have been calculated.

We hope that the above explanation answers your query. In case you have further queries, please let us know.

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@admin: Thanks a lot for your answer. Everything is much clearer now. I think this fractional ranking approach is a good idea.

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