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Arpa's blog

IOI vs CF performance: 2024 Edition
By Arpa, history, 3 hours ago, In English
CF ratings are unrelated to your IOI results. CF contests differ significantly from IOI contests.

❌ Wrong!

A higher CF rating, with a gap of at least 100, correlates with an 87% chance of achieving a better placement at IOI. In fact, the relationship between IOI placement and CF rating is strongly connected. The Pierson Correlation Coefficient for these two factors is -0.83.


Correlation between CF rating and IOI placement

❗ What is that outlier participant on the top-right? He is Jiyu Shen (PubabaOnO), with CF rating of 3000+, but it seems that he was unable to attend the contest 💔

Here are the statistics on CF ratings for each medal:

Medal Minimum Median
🥇 2029 2469
🥈 1501 2274
🥉 1637 2082

Additionally, I've discovered an interesting correlation: participants' ratings one year before IOI also correlate with their final ranks. By the way, some participants showed remarkable jumps in their ratings during that one-year period. Specifically, there were 4 participants with 1000+ growth in CF rating!



Correlation between CF rating a year before IOI and IOI placement

Based on this insight, I’ve trained a model that can predict your placement at IOI. If you’re curious about your predicted placement for IOI 2025, leave a comment! Note that as time passes, the model can determine your place more accurately. So you may comment again 6 months later to see the updated prediction.

Check out the similar blog for IOI 2019 here.

IMPORTANT: I've received massive downvotes recently, so I want to have the number of upvotes and downvotes separately. If you are going to upvote this blog, please click on this button too: .

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3 hours ago, # |
  Vote: I like it +19 Vote: I do not like it

What I find quite interesting is that difference between gold and bronze is only 400 points. Not a small amount, but it's by no means a large gap. I'm interested if something similar is at their OI level?

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    3 hours ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    I do believe being Red from CM is much harder than being CM from nothing. 7 out of 100 total CF user is CM, 4 out of 100 (+1900) CF user is Red. It's not just 400 rating difference due to non-linear nature of logarithms? is this correct term?

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    75 minutes ago, # ^ |
      Vote: I like it +7 Vote: I do not like it

    Reaching 2400 from 2000 is several times harder than reaching 2000 from 1600. For most people, it's nearly impossible. That's why the significance of a 400-point difference depends heavily on the rating range.

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3 hours ago, # |
  Vote: I like it +17 Vote: I do not like it

just a small detail, I believe Jiyu Shen was disqualified, but his performance was top 5 if I recall correctly, so it does still support your point

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    2 hours ago, # ^ |
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    Thanks for pointing that out. I wasn't aware of it. I noticed his scoresheet was empty and assumed it was due to his absence.

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3 hours ago, # |
  Vote: I like it -24 Vote: I do not like it

"unable to participate" kekw, how much did you get paid

i guess he couldn't do it without a phone, sad to see the rewriting of the history going underway

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105 minutes ago, # |
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Please predict my placement. Lol, hoping for at least bronze :sob:

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70 minutes ago, # |
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What if you remove everyone that hasn't done, say, 5 rated contest in the last 6 months? Otherwise, your data contains ratings that probably aren't "true".

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    61 minute(s) ago, # ^ |
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    I only included people who participated in at least a contest. I did what you say right now, and correlation got stronger just by 0.02 (=-0.84).

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62 minutes ago, # |
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Whats mine im curious

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    57 minutes ago, # ^ |
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    115! But personally I think you can easily reach silver.

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56 minutes ago, # |
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mine?

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    47 minutes ago, # ^ |
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    107, but your account is quite fresh. I think you can easily reach silver.

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55 minutes ago, # |
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Predict my placement too please

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    48 minutes ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    95, on the cut of silver and bronze.

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50 minutes ago, # |
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Can you predict mine placement?

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50 minutes ago, # |
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While the data does indicate correlation between CF rating and IOI result, I disagree that it's wrong to say "CF contests differ significantly from IOI contests". It is a very different style of contest: 2-3 hours and you must solve as quick as possible vs. 5 hours, no penalty for resubmission, subtasks etc.

Of course, being good at one will probably mean you are good at the other, since the core problem-solving skills are applicable to both. But personally I struggle to consistently perform on div 1s due to silly mistakes, running out of time or getting stuck on one problem for too long and having too high penalty even if I solve later problems. Meanwhile in an OI contest none of those factors are nearly as significant, and I had a very strong performance at IOI this year. Of course maybe this just means I need to train more on Codeforces...

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