Codechef Rating Predictor

Hello everyone!

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Codechef Rating Predictor

The delay in previous month rating changes + inspiration from CF Predictor and for the practice of a web-application, i tried to write a script that can predict rating changes from ongoing live contests @ Codechef.

While the actual delays in rating changes s/would be fixed, this script can help in predicting rating changes as new submissions are made, so hopefully it can be useful for Long contests :).

The script is written in nodejs and is based on open rating formulas available at this link.
The code for the project can be accessed here

Website is currently hosted on Openshift free servers and has few restrictions on use. Therefore the server might be slow or not responding during the period rating changes are calculated. Currently, ratings are expected to be updated every 15 minutes

I also tested rating changes on few past contests and the predictions were accurate within an error of 2 for almost everyone except the first rank (I have no idea why first rank predictions are wrong in some contests using current formulas)

Please note that project is still in beta stage and also actual changes might differ more due to changes in ranklist after plagiarism detection

Your feedback/suggestions would be appreciated

JUNE17 Links:



Few stats on JUNE17 Predictions. I matched ratings (All) of first 6391 users and the results were as follows:

Difference - No of users

  • 0 - 5868
  • 1 - 275
  • 2 - 125
  • 3 - 68
  • = 4 - 55

There were around 40 users having difference > 50. Turns out some usernames appears to be missing in the ranklist when sorted by rank and hence they were showing as last in the prediction list.

I ran the code again after fixing the above bug and results are better now (Maximum difference is 8)

  • 0 - 5900
  • 1 - 485
  • = 2 - 6

COOK83 Links:



The ratings are expected to update every 5 minute

Few stats, 4811/4820 predictions (for both all and cook-off predictions) were right. Rest have diff < 3 with the exception of rating prediction of first rank in cook off. Also, as @vikasj554 pointed out, few users got rating changed after initial update. (I still need to figure out why this happened). But even after this 4794/4820 predictions were accurate.

LTIME49 Links:


Lunchtime :

The ratings are again expected to update every 5 minute

JULY17 Links:


Long :

Update frequency: 10 mins


That is brilliant work! I always wonder what my rank would be after the contest but codechef’s delays leave me checking in everyday only to find out the ratings have not been updated.

Thanks a lot, buddy!!


but the links are showing 504 GATEWAY error

The CF predictor was/is incredibly useful. I imagine this would be too.
Nice work! :slight_smile:


Awesome tool buddy :slight_smile:

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You can try now. That was due to almost all available resources being used in calculation phase. I modified script to use less resources, so this error shouldn’t be occurring frequently now

Excellent Work.And one small suggestion can you sort the names if possible or is there any way to find my username quickly?

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Just press ctrl+f and enter your name.


Thanks a lot

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Amazing Work
Now really don’t need to much worry about my ratings change.

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starred on github.
Nice work dude.

according to this I’ll be loosing 31 points at the moment…
but great job!!!
good way to get a fair warning.

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Very nice work. To be honest, once I thought of doing this, guess I don’t need to now :). Your work is amazing. Thanks, we needed this.

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nice job mate :smiley:

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That’s some amazing work man :slight_smile:

Currently the links say “Application not available”. Excellent work by the way, I used the predictor during the June Long Challenge and it was very accurate in my case, appreciate the time you put into this.

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Hi, I believe this error is somehow due to free resources exhaustion. Refreshing a few times works though. Temporarily, I also uploaded latest generated ranklist here:

Exactly accurate (100%)

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great dude! really useful.

Very useful!! Great initiative!