MikeMirzayanov's blog

Saratov Summer School "Sazanka 2010"
By MikeMirzayanov, 15 years ago, translation, In English

The first information letter


General information


From 2nd to 12th August 2010 Saratov State University runs an international student summer school in computer programming. Teams of three people and individual participants are invited to take part in it.

The school will take place in a picturesque place at one of Saratov resort centers on the Volga bank. The participants will be provided comfortable rooms for 2-4 people and meals three times a day. The resort center owns a beach and sport grounds.

The school curriculum includes lectures by Saratov state university coaches, joint trainings, problems tutorials and topical workshops. The curriculum is designed for younger university students who aspire to achieve high results at programming competitions.

The fees are 15000 RUR (~ 500 USD) for a person. Moreover, each team or an individual participant should bring a laptop with the support of WI-FI.

All interested participants and teams should register at http://acm.sgu.ru/sazanka-2010/ till 10th June 2010. Don't postpone the registration, as the number of participants we can take is limited.

You can get additional information by e-mail mirzayanovmr[symbol-at]gmail.com. As since the official language of the school is Russian, the registration requires knowledge of Russian. Also it is recommended to view this page in Russian.

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Codeforces Beta Round #14 (Div. 2)
By MikeMirzayanov, 15 years ago, translation, In English
Today's round is not quite usual. The participants of the first division can register on it and to participate out of competition. This round will be some alpha-testing for this functionality, but for the next div. 2 round you can expect a stable version. 

This round prepared for you by: homo_sapiens, Julia, Nerevar, KudryashovIA and me. 

I want a high-ranking 
MikeMirzayanov

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Known issue
By MikeMirzayanov, 15 years ago, translation, In English
There is known issue which sometimes leads to the fact that with the start of contest we have to restart the application (the same goes for the end of the contest). Please do not panic if it happens. In worst cases it will take 2-3 minutes. I’m resolving this issue, but at the moment it is not yet completely resolved. Thank you for your understanding.

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Codeforces Beta Round #12 (Div. 2)
By MikeMirzayanov, 15 years ago, In English
Hello again. I hope nobody has forgotten to register?

In this contest we will try alpha of our chat - if something goes wrong, we turn it off: please do not panic:)

Links:
Problemsetters: Дмитрий Матов и Игорь Кудряшов. Thank them for their contributions.

I wish you to advance to the first division.
Mike Mirzayanov.

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Funny things on contests
By MikeMirzayanov, 15 years ago, translation, In English
Sometimes funny things happen on contests. On a recent training Ivan Fefer was unsuccessfully submitting one of the problems for a long time. After all he asked me. There followed this dialogue:
Ivan: - I have a question on the problem D.
Me: - What is the problem?
Ivan: - It is about a tree and requests.
Me: - So it's C.
Ivan: - ...oops... The question is removed ...

Do you have a funny story about something that happened to you during the contests?"

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Codeforces Beta Round #9
By MikeMirzayanov, 15 years ago, translation, In English
Welcome to Codeforces Beta Round # 9. 
The problems of this round prepared by Alex_KPR. Thank you, Alex_KPR. Also Nerevar participated in the contest preparation.

Julia, a special thanks to you for the excellent translations.

Wish you high rating,
MikeMirzayanov

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Tutorials crowdsourcing
By MikeMirzayanov, 15 years ago, translation, In English
In case you are not familiar with the term, this the way of filling the site with content by the joint effort of the community. You might read a Wikipedia entry.
Basically, the idea to apply crowdsourcing to contests tutorials seems quite natural, but… it works badly. As you see, it is not the first time there has been no one willing to help the community. The question is: why and what is the way-out?

Let’s discuss it together. What should be changed/improved in order to make contests tutorials appear at Codeforces?

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Codeforces Beta Round #8
By MikeMirzayanov, 15 years ago, In English
Welcome and good luck on the round! 

I'd like to remind that if you have any questions on the problems, the best way to ask them is to use the web interface on the problems page. 

Later in the same post we will discuss the round. 

Wish you high rating,
MikeMirzayanov.

UPD. For contest you may thanks team Saratov SU #5, namely, users Fefer, Gerald and Polichka.

UPD2. And better late than never: the presence of English statements we are obliged only to Julia. Many thanks to her for 8 wonderful translations of 8 rounds.

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Announcement of Codeforces Beta Round 8
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Codeforces Beta Round #7
By MikeMirzayanov, 15 years ago, translation, In English
The contest is rescheduled to start on 19:45.

Thank you all for participating in Codeforces Beta Round #7. I hope you enjoyed it. You may discuss the problems and system in comments. Please express your opinion, especially if you notice any inappropriate behavior. And as always, I will read with interest the suggestions for improvement.

From today on both-divisions contests ratings will be updated separately for each division. I. e. ratings will be calculated as if two contests (one per division) have taken place on the same problemset.

Also I would like to see someone who wants to write contest tutorial. This must be done in Russian and English languages. Of course you must solve the problem on either contest, or in the practice. If you have a desire to do it - write in comments. Your post will be published on the main page and later available on special link available from the contest page.

Many thanks to the contest problemssetters: RAD and e-maxx.

Good luck.

Ratings has been updated. Solutions are available for view.

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Announcement of Codeforces Beta Round 7
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Codeforces Beta Round #6
By MikeMirzayanov, 15 years ago, translation, In English
Welcome to the Codeforces Beta Round #6.

It will be good to see your feedback and impressions in the comments.

Wish you high rating,
MikeMirzayanov.

UPD. It seems the problem D has some tricky issues around judge solutions. Judge solutions will be fixed and the problem will be rejudged. If it will affect many participants, the contest will not be rated.

UPD 2. We have reduced constraints in the problem D and made rejudge. No solution passed tests. So the rejudge affected significantly only 4 participants, who solved it during the contest. But all of them increase their rating if we will count the contest as rated event. So we decided to make it rated and put problem with lowered constraints into the practice.

UPD 3. And by the way, the round tutorial is waiting for a volunteer. The tutorial should be in Russian and in English. It will be published on the homepage and later will be available via special link from the contest page.

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Source Code Viewing
By MikeMirzayanov, 15 years ago, translation, In English
Hello to everyone.

The latest news - now you are able to see the source code of the solution. During the contest you can view your own solutions only, but when the contest is finished you can view the solutions of any other participant. The table with the solutions is available via the problemset page, the solutions there are sorted by the program length. Pay attention, please, that you are free to change the sorting criteria using the option at the bottom of the table. 
There is another principle that gives you the chance to view the source codes of solved (during the contest or practice) solutions only. Personally, I regard the principle "everyone sees everything" as more suitable for our regular contests.  Am I right?

When you run a contest within your private community, you'll be able to set up your own principle for viewing solutions (or to switch off this function at all). But this functionality is under construction now. 

Wish you high rating,
MikeMirzayanov

UPD. Standings page is improved. You may double-click into a table cell (or use Ctrl+click) to view the submissions history.

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Codeforces Beta Round #5
By MikeMirzayanov, 15 years ago, translation, In English
Welcome and good luck on the round! 

I'd like to remind that if you have any questions on the problems, the best way to ask them is to use the web interface on the problems page. 

Later in the same post we will discuss the round. 

Wish you high rating,
MikeMirzayanov.

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Announcement of Codeforces Beta Round 5
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Time of Codeforces Beta Round #5
By MikeMirzayanov, 15 years ago, translation, In English
Hello, everybody. 

At this point we have already decided on the date of Codeforces Beta Round#5: it's Saturday, March 20. The exact time is still unknown. I do want to find the best time suitable for most participants. Please, express your ideas in the comments - of course, you should not come up with the time that suits only you, but suggest the most suitable time for the majority.  

Wish you high rating,
MikeMirzayanov

UPD.  Thanks to everybody who wrote comments - I've read them all. The venture proved to be useful. Without your help, I wouldn't have been able to take into consideration all those factors which can affect the number of participants.  After much thought, I've made a decision to schedule the round for 19:00 (Moscow time) - I think this option is convenient for most users of the site. It does not mean that we will not experiment with time in future - we will try morning contests, but I can't promise about 5:00:).

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Codeforces Beta Round #4
By MikeMirzayanov, 15 years ago, translation, In English
I propose to discuss here the issues and troubles associated with Codeforces Beta Round #4.  On our side, we identified three difficulties: 
  • Slow judging - apologize for the large queue, to the next round, I assume significantly increase the speed of judging;
  • Runtime errors on Python solutions - apparently the decision they want to load some library, which is prohibited by security reasons;
  • Sometimes incorrect runtime errors - apparently the result of the antivirus on testing servers, they will be turned off on the next rounds
Also express your impressions about the round.

P.S. And by the way, the round tutorial is waiting for a volunteer. It is desirable that it will be one of the leaders of today's competition. The tutorial should be in Russian and in English. It will be published on the homepage and later will be available via special link from the contest page.

UPD. The ratings have been updated.
UPD 2. Thanks to KudryashovIA for his help in making contest.

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Mistake in email notification
By MikeMirzayanov, 15 years ago, translation, In English
In email notification (in Russian) I've made a typo. The phrase "It starts on March 12 (Friday), 2010, 12:00" should be read as "It starts on March 12 (Friday), 2010, 15:00".

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Codeforces Beta Round #3
By MikeMirzayanov, 15 years ago, translation, In English
I propose to discuss here all that concerns Codeforces Beta Round #3. Of course, during the competition it is forbidden to write anything about the solution of problems and similar things  

For the time of this contest, we turned off the chat server. This does not mean that it will not operate in future - I think it is a convenient and efficient way to communicate during the competition and you may expect it in the future.  

Also I'd like to announce Codeforces Beta Round #4, which will be held next week. It will be for participants from the second division (non-rated users or those having less than 1500 rating points). We will try not to delay Codeforces Beta Round #5, which will be opened for all. 

Wish you high rating,
MikeMirzayanov

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Announcement of Codeforces Beta Round 3
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Codeforces Beta Round #3 - Thousand apologies
By MikeMirzayanov, 15 years ago, translation, In English

It seems everyone is in the know that Codeforces Beta Round#3 didn’t take place in the appointed time. Seemingly, it happened because of the increased popularity of the site, on the one hand, and some of our bugs, on the other. For sure, it’s a pity that things went in such a way. On the other part, if everything had failed during the contest, it would have been worse. The contest is rescheduled for Sunday, 15:00 (Moscow time). Please be sure to check here for the start time in your time zone: http://www.timeanddate.com/worldclock/fixedtime.html?&day=07&month=03&year=2010&hour=07&min=00&sec=0&p1=179

I’d like to remind you that the project is in Beta yet, and we’ll work on the problem and try to fix it.

Thanks for your understanding,
MikeMirzayanov

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Table of Ranks
By MikeMirzayanov, 15 years ago, translation, In English

According to The November Revolution of Colors and Titles, the text below is not an actual and just a historical document.

Not so long ago a new rating system was introduced at Codeforces. To complete the picture I’ll tell you about our Table of Ranks.

From this moment on all the participants will be given ranks that reflect their skills and abilities at such a hard field as computer science and problem solving. Judging by the results of previous rounds you will gain (or lose, I hope it’s not your case) points. If you score big success, you are promoted to a higher rank. You can see the dependence between rating and ranks in the table below. Moreover each rank has its color, which is reflected in the table.

RatingRank
0-1199Recruit
1200-1349Corporal
1350-1499Sergeant
1500-1649Lieutenant
1650-1799Captain
1800-1999Major
2000-2199Lt. Colonel
2200-2399Colonel
2400-2699General
2700+Marshall

As you have already noticed: we have only three captains in our regiment: vepifanov, gusakov, RAVEman. But I’m sure, after Codeforces Beta Round#3 we’ll have a number of promotions.

Wish you high rating,
MikeMirzayanov

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Codeforces Maintenance
By MikeMirzayanov, 15 years ago, translation, In English
Codeforces will be unavailable for up to 6 hours while we upgrade our infrastructure (March 3, 4PM - 10PM). Thank you for your understanding.

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Codeforces Rating System
By MikeMirzayanov, 15 years ago, translation, In English

As some users have already noticed - contest rating has been added to Codeforces. For now it is in beta too, but it looks very adequate. Here's how it is calculated.

Each person is characterized by their rating, the number R. If person A's rating is RA, and person B's is equal to RB, then the formula


gives the probability that A will get a higher position than B in the round final standings. By the way, here everything is very close to the Elo rating.

Before updating your rating after the end of the round, for each participant his seed is calculated, that is the place that the participant is expected to take in this competition. Thus, two things are known for each participant - his seed (the expected place) and rank (the actual place). Depending on the difference between these two values, your rating increases or decreases. If the difference is higher, your rating changes more.

There are a few technical points:

  • if it is the first contest for a participant, his seed is calculated as 1 + n / 2, where n is the total number of participants in the round;
  • changes in the ranking of contestants are multiplied by a correction factor such that allows the sum of ratings of the participants to remain unchanged (before and after the round).

As at TopCoder all users are divided into two divisions: the first (rating over 1500 1650) and the second (rating_ not more than 1500 1650). Not rated users fall into the second division automatically.

Wish you high rating,  

MikeMirzayanov

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Codeforces Beta Round #2
By MikeMirzayanov, 15 years ago, translation, In English

Thank you all for participating in Codeforces Beta Round # 2. I hope you enjoyed it. You may discuss the problems and system in comments. Please express your opinion, especially if you notice any inappropriate behavior. And as always, I will read with interest the suggestions for improvement.

Congratulations to the three leaders: RAVEman, GarnetCrow and ivan.popelyshev!

See you at Codeforces Beta Round # 3.

P.S. And by the way, the round tutorial is waiting for a volunteer. It is desirable that it will be one of the leaders of today's competition. The tutorial should be in Russian and in English. It will be published on the homepage and later will be available via special link from the contest page.

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Announcement of Codeforces Beta Round 2
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Codeforces Beta Round #1
By MikeMirzayanov, 15 years ago, translation, In English
In this topic I would like to raise issues around Codeforces Beta Round # 1. What did you like? What is not liked? What seemed uncomfortable? What can be changed to make participation more comfortable?  I wonder your opinion on contest web-interface. 

Please do not write about access the site with the address http://codeforces.net/ (I recommended to use http://codeforces.com:8081/). I guess the problem is around of Apache Virtual Hosts + AJP Connector. Something is configured incorrectly or doesn't work properly because , then it works so good. In short, I will correct. 

I'm waiting for your comments. And, of course, welcome to Codeforces Beta Round # 2. 

Also I would like to see someone who wants to write contest tutorial. This must be done in Russian and English languages. Of course you must solve the problem on either contest, or in the practice. If you have a desire to do it - write in comments. Your post will be published on the main page and later available on special link available from the contest page.

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If there are problems with site
By MikeMirzayanov, 15 years ago, translation, In English
You can try http://codeforces.com:8081/

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