# A surprise in store this new year!

EDIT: We have introduced a new rating system. Please have a look at this.

Hi guys,

We’re finally in the middle of Christmas season! A time for fun and joy and also giving each other lots and lots of presents! Our chef is always excited at this time of the year and cannot wait to reveal his gift for you all.

Are you all ready? *drum roll* With the new year will also come into place our brand new ‘Short Contest Ratings’!

Check out the salient features of our very exciting rating system :-

1. The ratings will take into account COOK01, COOK02, COOK04 and COOK05. COOK03 will not be considered as it was a team based contest.

2. A player will be rated (awarded rating points) in a contest if she has made at least one submission in the contest. If someone doesn’t make even a single submission in the contest then her rating will not change after that contest. (note that it may bring down her rankings).

3. It will be a seed based rating system modeled on the ELO rating. Reference – http://people.ksp.sk/~misof/publications/2009thesis.pdf page – 22.

4. The rating algorithm is a function which takes 2 inputs in the form of Ratings before this contest and Ranks in this contest and gives the final Rating as output. If a contestant participates for the first time in a contest then her previous rating is taken as some default value (say 1000).

5. Mathematical details of the algorithm are described here in brief :-

First for each pair of players (A,B) we calculate the probability of A defeating B and vice versa based on the ELO formula. Then for every player we calculate the sum of probability of defeating other players.

Lets say,
P[B, A(i)] = probability that B defeats A(i).
total[B] = summation of P[B][A(i)] over all A(i).
n = number_of_participants.

The expected rank of a player B in a contest,
E[B] = n – total[B].

We define regular factor for contestant B,
Regular_factor[B] = E[B] – Rank[B].

We have also added a bonus factor so that we can reward extra points to players who have been ranked higher in the contest.
bonus_factor[B] = n/rank[B].

Then for each participating contestant her rating is modified as follows:
New rating[B] = rating[B] + k * regular_factor[B] + m * bonus_factor[B].
Here k and m are constants to give appropriate weight to both the factors.”

Do send in your feedback and let us know what you think of this new rating system for short contests. We hope you are as excited about it as we are! 🙂

Best wishes for the new year to you all!

Cheers,
Team CodeChef

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## 47 Replies to “A surprise in store this new year!”

1. Vijay says:

I’m bad at understanding math. All I need to do is, participate in many contests and do my best in all of them 🙂

2. manoharsingh says:

Yeah!! Finally it comes…ratings for short term contests!… I am so excited!

shouldn’t ‘k’ be a (decreasing) function of the number of contests in which the contestant has participated, instead of a constant?

Good point. Thanks for the feedback. We will certainly consider this suggestion and decide if we want to make ‘k’ a decreasing function or not.

4. Roman says:

oh,that’s great!now all the short contests will become more interesting,exciting,stressful!
rlly thanks:)

5. Mkagenius says:

How about challenges and all…like that in tc.

6. Ankit Kumar says:

I am not able to find this short contest rating anywhere… When are you planing to launch it?

1. We are extremely sorry for the delay in the release of our new rating system. We are in the final stages of fine tuning the parameters to make the ratings as fair as we can. Please bear with us until then. We are trying our best to release it by the end of this week. And we hope, it will be worth the wait.

I solved a couple of qs in cook 05 but my ratings is still zero. Hasnt it been updated as yet??

1. CookOff’s are independent events than our long contests. The present rating system is only applicable to our long contests. We are building a new rating system for the short contests, and trying our best to put it up by the end of this week.

8. Keval Vora says:

My username is “kevalvora”. I accidentally solved a few questions of COOK05 while the contest was going on. So have I officially participated in COOK05? If yes, why is my rating/ranking not changed after the contest.

9. Shanmugam says:

I submitted one correct answer for May2012 , but still i dont see any rating for my Account. It says we are not able to find your country code. But actually i filled every detail of my address. Can u say y this is happening?

1. It’s not a problem that you are encountering, your ratings get updated at the end of each CodeChef’s Long and Short contest respectively. For this contest, the ratings were updated after the end of the contest i.e. on 11th May after 3:00 PM IST. Please check your rankings once again and let me know if you face any issues.

10. sp says:

ok the algorithm is very nice and fair.. but at the same time demoralizing too.. even after solving one prob of d contest today,my ranking and rating both went down. i am not saying that have done anything great or something by solving one prob. but at least i shud be given a bit of raise in the ranking.. my previous rank was 478 and in today’s contest i ended up at 361 so it shud improve a bit at least. just a stupid thought and feeling! 😛 kindly do something for us newbies! 😛 i know i sound totally insane but cant help desperately wanting to improve so.

11. Lokesh Khandelwal says:

Can you please share the values of k and m..You can mail me if u dont want to be it in public : My handle is phantom11..I promise not to disclose it to anyone ..

12. Uzma says:

when will i be able to see my ratings for long contest of july 2013???..it hasn’t uplaoded yet …showng an error dat unable to fined my country code …

1. Hi Uzma, we will be updating the rating of July 2013 soon. What error are you getting while selecting your country.

1. Uzma says:

I m not getting error while selecting my country…i’ve udated my profile correctly including my address n my country but it is not showing my ranking yet …showing Oops!! We didn’t find any country code for you.

13. Poorvak Kapoor says:

Poorvak Kapoor
Sir @admin i have submitted 3 program’s but my rating are still the same i.e. 0 it shows the error Oops we didnt find any country code for you,i’m from India and the competition is already over so am still waiting for my ratings to be updated!!! please do something…..

@admin I submitted one correct answer for Sep2013 , but still i dont see any rating for my Account. It says we are not able to find your country code. But actually i filled every detail of my address. i’m from India and the competition is already over so am still waiting for my ratings to be updated!!! please do something…

15. Ayesha says:

Missed it actually, as this is the fist time I am visiting this website. I will try to subscribe and hopefully I can make it to the next time.

1. Hi Sudhackar, it could be because you participated in many of contest but did not perform well. So, every time you participate, but do not perform, your ratings fall a bit. 🙂

1. Arpit says:

so if suddenly someone with negative rating performed well then rating will increase slowly or quickly??

16. tijoforyou says:

i’ve submitted more solutions than some guys….yet my rank is below them….after updates.how???

17. bhavya says:

hi,i stated coding in this website recently..i solved 2 practice problems and 1 contest(november 2013 ,which is going on)..my rating is 0 and my ranks are also not displayed(of course i dint do much still)..it is stating that they dont find my country code….can ny1 help me?

18. Saurabh says:

If some solves one problem in a contest his ratings goes down while if someone doesn’t solve any problem his rating doesn’t change. This is unfair.

19. Soumya Agrawal says:

Why is my ratings not getting change after short competitions..cook47 and 48..i have solved one and two questions respectively…my handle is ageekwall

20. Vaibhav Agarwal says:

Does the rankings improve when we solve practice problems.????

21. manish kumar says:

There is no mention of cook52 in my account profile. And my ratings were calculated assuming I solved 0 problems? Please Check

22. Yash Bhatnagar says:

I participated for the first time in the short contest, and was able to solve 1 problem in single attempt.However my ratings dropped from 1000 to 788.I was expecting it to increase atleast by a marginal amount.
Its demoralising.

23. Yash Bhatnagar says:

How can i suffer a loss on my ratings when i participated for the first time in a cook off? I mean I had a rating of 1000 earlier and even though i solved 1 problem on first attempt, my ratings were dropped?? I seems weird and is demoralizing to see that people who did not solve any question still had their ratings as 1000 while mine were reduced.

Can anyone help me understand or point out where i am wrong?

24. Vishal Batchu says:

Has May Lunchtime 2015 been considered yet for the user ratings? My rating has still not changed.

25. aman raj says:

my rating has not been improved even after making submissions in sept long challange…..

26. ROHIT RAO says: