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 (Crysfly), 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.
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?
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.
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.
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
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.
No he wasn't top 5.
Please predict my placement. Lol, hoping for at least bronze :sob:
177!
Wow, that is literally the last person who got bronze. Clutched haha
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".
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).
I'm a bit confused about what is going on your plots with the rating distribution of the gold medalists. For example, it looks like only in this last plot is there someone with rating just below 2000 in gold. But this plot should simply contain a subset of the data from the other plots. So that doesn't make any sense.
Thanks for reporting. There was a bug in calculating this plot. After recalculation, it added just 0.01 to the correlation. Here is the correct one.
Whats mine im curious
115! But personally I think you can easily reach silver.
OK guess we'll never know this year Since i fucked up my national OI horribly
💔
Nice pfp brother
mine?
107, but your account is quite fresh. I think you can easily reach silver.
Predict my placement too please
95, on the cut of silver and bronze.
Can you predict mine placement?
90, on the cut of silver and bronze.
Pretty good, I got 85th on IOI 2024.
the model was probably trained on your data lol
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...
ngl gold on IOI as a master is very based
I am interested!
171
Can you predict mine
135
I actually got 199 :(
Please note: The model doesn't predict the placement in IOI 2024, it also take into account the growth you'll have during the time you have until IOI 2025.
Oh I didn't notice. That's nice. I also think that my rating actually says that I should rank better than I actually did in IOI
Can you predict mine please
115
Predict mine please
137
Can you predict mine please
85! Silver.
❌
Can you predict mine please ?
149
Thanks ! And now ?
139
Could you please predict mine?
185
Could you do again?
199
would like to know mine over the course of time. grinding for expert rn
212
Mine plzzz
106
please predict mine
72
mine
229
so Orange or higher in cf = almost guaranteed IOI medalist
quite interesting, cf rating is so much valuable than what I thought
It's not. It's just that when reahing 2100+ level (preferably, from div1, reaching master from one lucky div2 contest isn't what i really mean...) you have enough skill/common sense, call it whatever you want, to be able to get medal even in you worst performance case. That's why it's (almost) always guaranteed IOI medal. You can't describe any medal with certain required cf rating (there is an actual CM gold medalist this year as well as there are many GMs in silver/bronze), but you can give such a "lower bound" for skill level (which div1 masters characterize pretty well). Everything else is mostly luck.
the classic "correlation does not imply causation".
How does the fit look if you only look at silver and golds? I feel like getting bronze on IOI is fairly easy once you have some solid CP base, so it probably correlates with higher rating on any website. For the distinction of silver vs gold, though, it becomes a lot more critical to practice the format and the problem styles, so something like CF shouldn't be too predictive (except maybe in the 3000+ rating, which just signifies insane abilities overall).
a lot of it is also just random noise due to ioi being only a 2 day event. Even previous IOI results won't correlate with future IOI results. For example, consider https://stats.ioinformatics.org/people/1144
I'm well aware that there's a lot of variation (me), but still might be somewhat interesting to see the correlation. But you're probably right that there's too much noise to get anything useful from this one year.
Could you predict mine, please?
140
What about mine?
254
What's the significance of this score?
It's your predicted placement in IOI 2025.
Can you predict mine please?
104
Actual rank: 71!
Hope you to calculate Guo Yuchong,Huang Luotian and Shen Jiyu's real score,not the score after they were punished to get a more precise answer.
What's your prediction about me?
148
Mine?
107
Actual rank: 274.
mine ?
I don't think my model can predict correctly for unrated account. Go participate in at least 5 contests and come back.
mine?
142
Mine please :)
73
Can you predict mine
183
Can you predict my placement?
168
Can you predict mine?
Unsuccessful hacking attempt.
LOL
Which is my prediction?
156
Thanks
Which is my prediction?
148
Actual rank: 156!
can you help me check my predictions?
223
please predict mine
47
Can you predict mine please
174
Actual rank: 121.
Curious, Arpa:
What does this analysis (I mean the predictions part) look for other IOIs? [Since you mentioned you can predict performance in IOI 2025, that would probably mean older accounts get an "unfair advantage" due to more time to practice?]
Also, this analysis has been done for CF ratings at the time of IOI, right? [Which may not be the max rating of the said account till IOI time]
I wonder how the graphs / plots look if you consider the max ratings?
Also, just for fun: can you predict mine please?
Do you mean in IOI 2026+? I think that there is no accurate prediction.
Here is the plot for max rating, but note that it shows a bit less correlation with the IOI result (Pierson Coefficient is 0.80). It seems very similar.
The last contest you participated in is very old and can't be used for prediction.
Actually, I meant something like IOI 2024, 2023, 2022 etc by "other IOIs"
I basically meant that, since older accounts get "more time to practice" (example: someone's last contest is in 2023, so they get two years for IOI 2025 compared to someone whose last contest is in 2024), so perhaps would be better to think in terms of IOI of <"last contest" + 1 year> or something.
Regarding the max rating plot, that's also interesting how it has very slightly lower correlation, but still strong.
Can you predict mine?
233
Thanks! What about now ?
232!
woww, I've developed lol( I didn't participated a lot of contests in this account). See you in 5 months :D
Hey, can you predict mine now :D
217
Hey, can you check now lol
Are you going to participate in IOI 2025?
no, but training for 2026
Unfortunately, I found an issue in my predictor I hope I can fix it before IOI 2026 and we can have it by then.
okay thanks! good luck
Can you tell us how you predict placement of people ? Is that possible to make a website that can predict placement of users by their handle ?
I'm thinking about that.
What about mine?
114
Can you please predict mine?
178
Can you predict mine please?
87
I think the following adjustments would make it more accurate:
1) filter to those who have participated in at least six contests, because otherwise their rating would be downwardly biased due to the CF base rating of 1400 being credited over six rounds, and
2) filter to those who joined at least once over the past six months
me tooooo....please
220
Can you predict mine?
90
Close, I am actually 89th.
Please note: The model doesn't predict the placement in IOI 2024, it also take into account the growth you'll have during the time you have until IOI 2025.
Could you calculate it after 2100? I am actively thinking about leaving codeforces
2100 is where the fun begins
Lmao I agree. But sadly olympiads aint no fun and implementation and algorithm heavy
It's funny that what used to be people asking for their future rating to be predicted turned into people asking for a prediction of their expected IOI ranking XD
Now on a more serious note, great job for your work, now as a follow up, it would be interesting to see whether this metric remained the same over the years and how can these results reflect a country's improvement or downfall in terms of future IOI performances and what can we learn from this.
Whats mine im curious
120
Can you predict mine please.
221
Can you predict mine please
142
Predict mine please
241
I'm not an expert in these areas but it might simply be correlation and not causation. meaning that practicing cf contests might not directly improve your IOI performance (though it probably does a little bit, or up to a certain point), but people with higher ranking at IOI might have been more skilled at solving cf problems.
mine?
is it worth participating in IOI ??
278. IOI is always worth participating in!
Thank you !
We need 2025 edition now
Mine?
118
Btw Jiyu Shen participated in the contest. He would have gotten the gold medal if he hadn't been disqualified.
Mine?
139
What about mine plz qwq?
-38, good luck!
mine?
80
Actual rank: 126.
BTW Arpa,
I think there might be one more thing to take into account, especially at higher medal levels like Gold and all.
So, I would guess that most of the IOI people would be training on IOI-like problem sets (of course they probably often also train on CF, to maintain speed / form, different problems, just for fun and practice etc)
That said, often you'd find that some IOI people, especially at the top of IOI, like Gold etc, have a lot of skill, but it is not THAT much reflected in their CF rating, maybe because they might have done too few CF contests, so ratings didn't converge. Or maybe their "IOI skill" is high, but "CF skill" lags behind.
So, because of that, it might not be fully correct to say something like: "2469 CF rating roughly means IOI Gold level".
Of course I agree that "general CP skill" is a thing and CF is a good measure of that, so that is why the fact that "2100+ master = almost guaranteed IOI medalist (at least bronze)" is probably true.
I just wonder if we can do some sort of math, or something to account for this "lag" in "IOI skill" vs "CF skill" (or also the fact that some people's CF accounts lag behind due to less participations), and then get some sort of an "equivalent" of an IOI medal.
Example: maybe we can say: "while the median IOI Gold is 2469 rated on CF, something like +100 may be a better representation, so something like 2550 on CF would imply kinda skills comparable to getting Gold on IOI" Basically, IOI gold implies 2469 BUT we can't quite reverse this implication directly, more correct might be to say: 2550 CF implies median IOI Gold, or something like that?
I am just putting out thoughts here, and curious about your thoughts. Would love to see other ways of looking at this (or any other mathematical insights here)
Also, to be fair. cc: Arpa I just noticed there are data points in your plot which have like 1500-1600 or something rating and a bronze / silver medal at the IOI (As you mention in the rating cutoffs)
I think this is nowhere near their true skill. It's just that they probably didn't do enough contests on CF.
Wonder if some data cleaning here is needed.
Also, your prediction model seems to map newbie / pupil level people also into some IOI rank like 250. (of course, some countries may be much much easier to qualify for the IOI from, and some like China are harder to qualify from than win IOI Gold), but still seems a bit too optimistic.
One more small potential thing to think about
cc: Arpa
This statement: "A higher CF rating, with a gap of at least 100, correlates with an 87% chance of achieving a better placement at IOI. "
Might be a bit of an overestimate, because given n people, it considers all n^2 / 2 pairs of ratings. Here, if some two points differ by say 500-600 rating or more, then they truly are in different leagues, so the stronger one probably WILL rank higher.
However, we shouldn't count such cases in the "87% success" cases perhaps, because it is obvious that someone rated 1900 will probably lose to someone rated 2500. This will trivially increase the 87% number.
The more important information is probably something like: "can a +100 or +150 jump in rating create a higher placement?". Probably considering all pairs with a rating gap of 100-150 points or something like that would be better?
Otherwise, a majority (or large fraction) of the N^2 pairs, would probably be with a > 500 gap or something, which skews things
Thoughts?
I can share all the data with you to investigate what you want.
Sure, thanks!
Will DM you.
mine?
188
Mine?
202
Thanks a lot
mine?
70
Thanks! What about now?
Congrats! 49!
Actual rank: 67!
Mine? pls
254
Actual rank: 290!
Can you predict mine, please ?
And thank you ^_^
183
Actual rank: 209!
Would you predict me pls?
205
A note for people who put comments onward: As we get closer to IOI 2025, the prediction becomes more precise. Also, the window for growing narrows, so it's normal to see people with the same rating as you get better placement prediction in the past (like 5 months ago).
Would you be able to predict mine?
178
can you predict my placement? (please not last)
264
can you predict mine pls?
218
im baaaackk (i want a good rank :pray:) could you predict mine please?
You're telling me that I'm IOI bronze material? No way
Predict mine please
139
Can you predict mine?
180
Actual rank: 194!
Mine ?? Hhh
367
could you predict mine please
228
Predict mine please (and if I have bronze or not)
mine as well pls
397
160
Why didn't you just provide the regression equation? It would save you a lot of commenting, unless you just wanted to keep the blog relevant, which would actually be pretty smart.
It's not a fixed regression. It changes with time! Read above.
I see it as a typical idea btw.
Predict my place please
59! Great.
Actual rank: 88!
could you predict mine please