Over the past few weeks, we've been hard at work improving DMOJ's backend for a better user experience, and today we've finally made these changes live.

Server Upgrades

The servers backing DMOJ have not received upgrades in years, and were constantly dangerously close to hitting CPU and memory limits.

After some particularly successful Black Friday shopping, we're happy to announce we've doubled the resources available to our frontend servers, and octupled those of our database. We've also split up several other services onto smaller machines dedicated to running them. Judging servers have not been updated, so expect no change in submission runtimes.

All servers have also been migrated from a New York datacenter to one in Montréal, so Canadian users should experience improved connectivity (international accesses should not be affected significantly). In our tests, the new servers render pages 20-40% faster than the old ones, and leave a lot of room for increased load during peak times.

Since this required massive changes to our networking setup behind-the-scenes, it's possible that there might be slight issues in the next few days.

New Facebook-friendly CDN

We've heard reports of DMOJ links being blocked on Facebook and Messenger, and have taken steps to resolve this. Previously, resources were being served off of dmoj.ml (for site resources) and camo.dmuser.ml (for SSL-proxied user content) — as of recently, Facebook blocks sites linking .ml TLD domains. As a result, we now serve off of dmoj.algome.me and camo.algome.me, respectively. If you use NoScript, uMatrix, or similar script-blocking browser plugins, you will have to allow these domains to use DMOJ.

Facebook issues should clear up within a few days.

Minor Judge Changes

The judge has seen a lot of work recently, largely for improving stability. Among others,

• it has been ported to Python 3, so there might be some issues popping up on complex problems
• it now disables address-space layout randomization on submissions (this means segfaults should be more reproducible)
• the sandbox permissions have been tweaked
• all JVM-based languages (Java, Kotlin, Groovy, etc.) now use -XX:+UseSerialGC
• Java 10 support has been added
• Java 7 support has been dropped, and all Java 7 submissions have been remapped to Java 8
• C11 support has been added
• Scala can be used with extends App now
• support for R has been dropped

Thanks for participating in the TLE '17 November contest!

The winners are:

1. y0105w49
2. zhouzixiang2004
3. Xylofo
4. r3mark
5. tankturtle

Editorials for each of the problems will be uploaded to the respective problem pages.

We hope you enjoyed the contest, and see you next month!

We're excited to invite you to the third Thorndeau Logic Evaluation of the 2017-18 school year!

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

Thanks for participating in the DMOPC '17 November contest!

The winners are:

1. REEmark (perfect score)
2. mmaxio (perfect score)
3. y0105w49
4. zhouzixiang2004
5. kobortor

Editorials for each of the problems have been uploaded to the respective problem pages.

We hope you enjoyed the contest, and see you next month!

Additionally, mmaxio found an error in the P2 problem statement. This round will still be rated, but if anyone feels that they were affected by this mistake, then comment or contact us on Slack before the next contest, and we will cancel that your rating change from this contest.

Starting this year, there will be a couple changes to the DMOPC/DMPG.

Starting with this DMOPC:

1. The DMOPC will return to being a monthly contest, from last year's almost monthly format.
2. The top 20 Canadian High School contestants across all rounds will automatically qualify for the DMPG Gold Division.

As for the DMPG:

1. There will still be 3 divisions: Bronze, Silver, and Gold.
2. The Bronze and Silver Divisions will be open to all.
3. The Gold Division will be open to the top 20 Canadian High School contestants across the DMOPC rounds, and there will be prizes given to the top coders.

Note that this is subject to change.

On Tuesday, November 14th, we'll be hosting the November Don Mills Open Programming Contest!

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

Contestants may participate in any 3-hour window between noon EST of Nov. 14th and noon EST of Nov. 15th. Please see the contest page for more details.

See you soon!

Thanks for participating in the TLE '17 October contest!

The winners are:

1. y0105w49
2. r3mark
3. zhouzixiang2004
4. bruce
5. wleung_bvg

Editorials for each of the problems will be uploaded to the respective problem pages.

We hope you enjoyed the contest, and see you next month!

We're excited to invite you to the second Thorndeau Logic Evaluation of the 2017-18 school year!

Anyone with a DMOJ account is welcome to participate and anyone without one is welcome to register and participate.

The TLE '17 October contest will be a 3-hour virtual contest, which will allow contestants to participate in any 3-hour window from 4:00 PM EDT to 11:59 PM EDT on October 27, 2017. Please see the contest page for more details.

See you soon!

The DWITE Online Computer Programming Contest was a popular contest that ran from 2002 until its discontinuation in 2012.

Since the data is publicly available (and had been lying around on our servers for the better part of 2 years), we've released the first batch of DWITE problems on the DMOJ. There's 150 in all, which will be released in full over the next few days. You can view them here.

Many thanks to Cthulhu, aeternalis1, BenjaminBLi, and kipply who helped format the questions.

Since there's over a hundred new problems, chances are high that there will be formatting errors in the them: if you find any, please do let us know on Slack.

Thanks for participating in the DMOPC '17 October contest!

The winners are:

1. tankturtle (perfect score)
2. ivan100sic (perfect score)
3. y0105w49 (perfect score)
4. d (perfect score)
5. bruce (perfect score)

Editorials for each of the problems will be uploaded to the respective problem pages.

We hope you enjoyed the contest, and see you next month!

On Tuesday, October 10th, we'll be hosting the October Don Mills Open Programming Contest!

Anyone with a DMOJ account is welcome to participate, and anyone without one is welcome to register and participate.

Contestants may participate in any 3-hour window between noon EST of Oct. 10th and noon EST of Oct. 11th. Please see the contest page for more details.

See you soon!

Thanks for participating in the TLE '17 September contest!

The winners are:

1. bqi343
2. y0105w49
3. r3mark
4. Paradox
5. zhouzixiang2004

Editorials for each of the problems will be uploaded to the respective problem pages.

We hope you enjoyed the contest, and see you next month!

We're excited to invite you to the first Thorndeau Logic Evaluation of the 2017-18 school year!

The TLE this year will be a combined effort of Pierre Elliott Trudeau High School and Thornhill Secondary School students and alumni. Anyone with a DMOJ account is welcome to participate and anyone without one is welcome to register and participate.

The TLE '17 September contest will be a 3-hour virtual contest, which will allow contestants to participate in any 3-hour window from 4:00 PM EDT to 11:00 PM EDT on September 29, 2017. Please see the contest page for more details.

See you soon!

Thanks to everyone who participated, and congratulations to the winners!

1. bqi343
2. y0105w49
3. imaxblue
4. r3mark
5. Eliden

It's that time of the (school) year again, and to celebrate, we present the Back to School '17 contest! Get back into your tip top programming shape and start the school year with a new rating!

Back to School '17 will consist of 8 problems, with difficulty ranging between CCC Junior to IOI level.

You can choose a single 4 hour period between September 9 and September 10 EDT.

See the contest page for more details.

Thanks for participating in BFS '17!

The winners are:

1. bqi343
2. imaxblue
3. d

The winners will be contacted shortly about their prizes. Editorials will also be up shortly on the respective problem pages. In the meanwhile, we ask all contest participants to fill out a quick survey so we can improve future contests.

Survey here

We hope you see you next year!

Summer is just about over, and school is around the corner. We hope you had a great summer, and we want to make your school year even greater by kicking off with a new rated contest, including Amazon gift cards as prizes!

The contest will take place in a 2-hour window anywhere from Friday 3:30 PM - midnight EDT, and will consist of 6 problems of CCC Junior - CCC Senior difficulty.

See the contest page for details on contest rules and prizes.

Thank you to everyone for coming out to the 3rd annual Don Mills Programming Gala!

Congratulations to our winners:

Gold Division

1. ZQFMGB12
2. r3mark
3. imaxblue, WilliamH

Silver Division

1. Paradox
2. Tan, lpang
3. sunnylancoder, fungucide420

Bronze Division

1. Day, putonium
2. DishonestHips, Hypnova
3. Gthtjkt

We hope to see you all next year! A link to the archive can be found here.

As the academic year comes to an end, we'll be holding our final DMOPC in the form of the Don Mills Programming Gala.

This event will take place at Don Mills C.I. on Monday, May 15^th.

The contest will be split into three divisions of increasing difficulty, with prizes awarded to the top competitors. For interested competitors unable to attend the on-site event, we will also be hosting mirrors of the divisions, open for anyone to participate in.

Space is limited, so sign up soon! More details and registration options may be found here. You can find the results of last year's DMPG here.

Registration is now closed. Thank you for your continued interest.