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ITU at NCPC 2019 (5 October)

This page summarises the preparation for ITU students for the Nordic Collegiate Programming Competition (»Danmarksmesterskaberne i Programmering«) for 2019

The Nordic Collegiate Programming Competition (NCPC) is a programming and problem solving event held every year. Teams of 3 programmers try to solve as many problems as they can (from a list of a dozen or so tasks) in five hours. The NCPC is open to all, but in order to compete in the “official” part (placing in the national championship or proceeding to the European or world finals), you need to be a university student, and you need to register in advance and participate on site. That is also the most fun and satisfying experience.

How difficult is this?

This is for you. If you have programming skills corresponding to a single ITU introductory programming course, you should be able to solve 1–2 problems. You should feel very good about that. If you have even taken an introductory algorithms class (or other problem solving class) then maybe 3–4 questions are within reach, which puts you very high on the list. You can look at last years’ standing for all of Denmark; as you can see this event is highly welcoming of newcomers. (Don’t get distracted by the monstrous performances of the top participants; think of it like running the Berlin marathon — you don’t feel bad about being slower than the world record holder in the same race).

The event (»Danmarksmesterskaberne i programmering«)

The Danish events label themselves Danish Championships, and typically take place in Aarhus, Odense, and Copenhagen. ITU Students are encouraged to participate in the Copenhagen event hosted at KU, and supported by NetCompany and JobIndex.

If you want some inspiration, here is a hyggelig film about the 2016 event:

You can also look at the

  • web site for NCPC 2018 (last year), where you can see the team names and how well they did (under Final standings), read the problems, and look at the slides explaining their solutions. As you can see, there were 0 ITU teams. We want to change this.

Preparation at ITU

You should totally participate. If you’re on your 2nd year of studies and enjoy programming, problem solving, and collaborating, this is a brilliant, engaging, and intellectually and socially satisfying way to improve your skills – it is also great team building. And boy, does it look good on your cv.

  • Create a team. You want to create a team, maximally (and preferably) of 3 people, and find a suitably painful team name. If you don’t yet have a team, we will probably be able to create some during September. If you want to seriously compete, you need to read the rules for participating in the official championships, see the event web site. Or you can be like me and just participate for the fun of it. Align your expectations with your friends.
  • Chat channel: https://talk.itu.dk/channel/dmprog-ncpc-2019 : a chat channel at talk.itu.dk for this event. If you’re an ITU student, you already have an account. We’ll use this to communicate about pizza, problems, teams formation, news, etc.
  • NCPC Coaching Fridays at ITU at 15: Most Fridays at 15–16, starting 30 August, one of the ITU teachers will be available (room to be announced) for some coaching. Among other things, we’ll go through last year’s NCPC problems, point to other good material, discuss strategy and preparation. See the bottom of this page for an overview.
  • Bjarki’s course. Bjarki Ágúst Guðmundsson maintains a very ambitious course about competitive programming at https://algo.is. Includes links to relevant open Kattis exercises. No matter where you are in your skill development, there should be a module or two for you that makes you better.
  • Johan’s book. Johan Sannemo, Principles of algorithmic problem solving. Similar to Bjarki’s course, slightly different format and focus.
  • Grind. Log on to open.kattis.com. Sort the problems by difficulty and solve them from the top. Or search for NCPC to find old contest problems.
  • Teambuild. Do some programming in your team in order to understand your group’s dynamics. (The contest is with a single computer, so only one person at a time is typically typing.) Agree on one or two languages. (Python 2 and Java both are good choices.)
  • Select written material. You can bring any written material. So: Learn not to rely on on-line material (you can’t google stackoverflow during the contests) and find out which written you actually need and can navigate (say, a programming language reference, but not all 4 volumes of the Art of Computer Programming). You can even maintain your own evolving document, with often-forgotten code snippets, standard templates, hints to yourself, your editor configuration, soothing picture of a kitten, etc. Here’s an example from a very experienced partipant (Måns Magnusson), heavily focussing on algorithms: https://github.com/exoji2e/notebook.
  • Warm-up event Friday 20 September 16-19. JobIndex will host a 3 hour warm-up event for the Danish Championships (not on Kattis, but on the Sphere server at https://www.spoj.com/DMWARM19/). You’ll have to register for that on the server. (Previous events can be seen by changing the URL in the obvious fashion.) We’ll host the event simultaneously at ITU in some room (to be announced), registered students will be treated to Pizza and soft drinks by the Computer Science Department.
  • Another warm-up event. The Kattis people probably also will host a warm-up event, presumably for the full 5 hours of a standard competition, but the details remain unclear at this point. If it works out: Free Pizza at ITU again.

Coaching Fridays

These are extremely informal meetings. The expected skill set that of 2nd year Software students, but everybody is welcome. We’ll see if this is useful at all.

  • 30 Aug, 13-14. 2A08. (Thore). Welcome. Kattis basics, NCPC basics, tips and tricks, questions and answers. Solution of NCPC 2018 problem B–babybites (where Thore’s team was 1st last year!) and C–codecleanups.
  • 6 Sep, 15-16. Somewhere. (Thore) H–houselawn, greedy algorithms, I-intergalactic bidding.
  • 13 Sep, 15-16. Somewhere. (Thore) Graph problems. deliverydelays (very hard! we didn’t manage to solve it)
  • (20 Sep): Maybe no coaching, since there’s a warm-up event. at 16.

Worrying about superintelligence is like worrying about overpopulation on the Sun.

Worrying about artificial intelligence is like worrying about overpopulation in Bangladesh.

Will Code for Drinks @ Scrollbar, 2nd edition

On Friday 12 April, we ran another social coding event in the IT University of Copenhagen Friday bar ScrollBar. “We” is two colleagues (Martin Aumüller and Troels Bjerre Lund) and myself. This is the second time we try this, and it was a big success again. More than 50 teams participated, more than 40 solved at least 3 problems(!), and two of the ITU student teams solved 5 problems(!). The atmosphere was just great. Scrollbar was filled with teams of people gathered around laptops, paper, and drinks – typing, laughing, smiling, arguing, drinking, fist-pumping, thinking, and snogging.

The target audience is 1st years students on ITU’s various programmes, and that audience has matured a lot since the Fall. We decided to make the selection of problems a lot harder, with 6 problems (compared to 4 in the Fall), one of them pretty challenging.

We used the Kattis problem to host the event, using publicly available problems. The even site is https://open.kattis.com/contests/fwmxyb, and the problems were Križaljka, Pig Latin,Opening Ceremony, Datum, Entering the Time, and Worst Weather Ever.

In the organising group, we spend a lot of time on problem selection, and I’m again very happy with the resulting set. All the problems were immediately appealing, as well as easy to debug locally. (You can quickly make your own inputs for many of them, and verify your implementation’s answer with your own eyes.) Most of these problems require zero algorithmic insight at all and can be solved in interpreted Python 3 within the time limit. For one problem you need to sort, and another uses binary search. Except for one problem, all were easy-to-medium and don’t involve a lot of code. (My own solutions require 3, 9, 15, 15, 43, and 45 lines of python code.) For most of the problems, it’s clear “what to do,” but there are still some design choices to make, a lot of edge cases to avoid or handle, and a tiny bit of problem solving.

After a lot of soul-searching, we added a single hard problem, F, in order to keep even the experts among the audience busy – the event was graced by the presence of some very, very experienced competitive programmers. There was some good-natured sniping among these groups: the expected presence of an expert team from Sweden led to the creation of a Danish-German team of ITU employees named for Ulrik Gyldenløve, who fought victoriously against the Swedes in 17th century.

Scoreboard Hacking

To maintain the social aspect of the event, we decided to stick with a common scoreboard projected against the wall of the bar. It provides some kind of shared visual presence even for the non-coding guests at the bar. For this, we managed to implement one of the ideas from the Fall: the non-competitive ordering.

Here’s how the final standings of the event look using the standard Kattis scoreboard:

The standard Kattis scoreboard is sorted by number of solved problems; ties are broken on total time; the board also shows failed attempts.

We worry a lot about de-emphasizing the competitive aspect of the event, which lead us to rethink the scoreboard design. “Our” event is about people working in teams and solving problems. Once this is realised, the the information design is clear. We don’t want the board to include the team rank, or various timings, nor the documentation of failure. Instead, the board is about teams and solved problems, as well as the overall timer.

The transformed Will Code for Drinks-scoreboard.

“Our” board is sorted by most recent solve, so that every team gets a brief moment at the top. Team members could proudly walk up to the bar, announce their team name which was shown at the top of the score board, and receive their free drink. This worked spectacularly; people were sooo happy.

Hiding the unwanted table rows and re-ordering the board required nontrivial javascript-hacking using the Tampermonkey userscript manager in the Firefox web browser, mostly done by Tobias Christiani. (We discussed other ways of implementing the idea, but this one turned out to be easiest and least intrusive.) While we were at it, we changed some of the CSS style information to keep the design in sync with ScrollBar’s visual identity. It looks nicer, and it is nicer than the original.

Next event?

The next Will Code for Drinks will certainly happen in the Fall of 2019. I remain frustrated about how hard it is to attract inexperienced programmers – my ambition is to make 1st-year students aware of how much they can already do with their skill set. Martin, Troels, and I do provide help with problem solving and debugging, wearing silly hats. This works well for those inexperienced programmers who actually show up to the event, but I would like there to be more than a few handful of those.

One idea is to arrange a separate event specifically aimed at 1st-semester students, and advertise it directly to that population. “Will Hello World for Drinks?” in October, only 1st year students can register, lots of TA support? Followed by standard “Will Code for Drinks” for everybody in late November? Or is this exactly wrong because of the separation? Talk to me if you have an idea. Buy me a beer first.

Will Code for Drinks @ Scrollbar 2018

Homemade poster for the event

I am foremost a teacher, and I care a lot about introductory programming, computational thinking, algorithms, and the social environment of a university.

As an experiment in “social coding,” we implemented an event called “Will Code for Drinks @ Scrollbar” in the Friday bar at IT University of Copenhagen on 23 November 2018. The basic idea is to get beginning programmers—this includes 1st semester students and professors—together for a few hours, solve some well-defined programming exercises, and get a drink for each solved exercise.

Preparation

The idea was born over a couple of lunches with colleagues, and thanks to the enthusiasm of Martin Aumüller and Troels Lund it quickly developed momentum.

The platform we used for this is Kattis (open.kattis.com), which is a well-working system developed for programming competitions. Kattis comes with thousands of extremely well-done exercises, a reliable server with an accessible web interface, and very simple procedures for registering individuals, forming teams, and hosting contests.

Preparation included:

  1. Establishing rapport with the ITU Friday bar—a student-run organisation that hosts a social event every Friday afternoon during the semester. They loved the idea, and we were able to find a free date where no other ScrollBar event or theme (Halloween) was already planned, and no other ITU event (Board Game night!) was scheduled elsewhere in the house by one of the many other social committees.
  2. Learning Kattis and solving dozens of exercises there in order to find a selection of the event. The idea was that students with very little programming experience were supposed to at least solve one exercise, possibly with help, during the event. The selection we ended up with were Baby Bites, Spavanac, the lovely Trik, and the somewhat harder Bank Queue. We figured that 3 drinks are enough for anybody, and wanted a more challenging problem to keep everybody engaged during the event.
  3. Spreading the word among first-year programming teachers and their students. During the weeks up the event, our enthusiasm infected several students, who registered on Kattis and started grinding in preparation.
  4. Decisions, decisions… should the event be called “Will Code for Beer” instead? Drink or drinks? How competitive should we make it?
  5. Creating a visual identity. My original plan was to use a lot of images of various people holding cardboard “Will Code for Drinks” signs. In the end, it was too much work (after talking to the communications department about GDPR), and I cobbled together a clean visual identity on my computer in a couple of minutes. Another reason to reject the hobo-theme is that it possibly repels students who are concerned about appearances.
  6. Find some way to pay for the resulting bar tab, and that will be acceptable to the Accounting and Finances section.
  7. Design and order caps so that assistants (Martin, Troels, and myself) would be visible during the contest. Alas, the caps were not delivered on time.
An early experiment in developing a visual identity for the event. In the end, I rejected this direction, despite the great resonance among students and colleagues, for purely aesthetic reasons.

During the event

The event was “just” a contest on the open Kattis server  https://open.kattis.com/contests/f4ktq9

The moment the contest started at 15:30, we had most of the students in the same room adjacent to the bar, so we could help with Kattis registration, logging in, reading from standard input, etc. After that, participants slowly moved into ScrollBar and the ITU Atrium. We kept ourselves visible and available, and helped with programming and problem solving.

After

I spent a few hours writing emails to individual groups that I had talked to during the contest, explaining other approaches to specific tasks. Then I sent a brief thank-you note to all participants that I could identify and invited feed-back and suggestions for improvement. This was quite boring, I had to identify partipants  who had registered under their own name on Kattis and had a name I could uniquely find in the ITU student roster.

Evaluation

This was supposed to be a test run, and I had hoped for 5 teams of students. In reality, slightly over 50 teams registered, with 130 participants. Stunning success!

Will Code for Drinks @ ScrollBar 2018 in full activity. Photo by Troels Lund.

Of the participants I was able to identify, 48 are first-semester students. These were the intended target group. More that half of the students are from the educations hosted by the Computer Science department, but all of ITU’s student populations were present. 45 teams solved at least one problem, 35 teams solved three. 10 teams solved all four problems; this includes the teams consisting of faculty members and Ph.D. students. Phew!

In the end, the “damage” was 183 beers, 80 cocktails, and 8 soft drinks. In total, students solved 132 programming exercises in 2.5 hours, and fun was had. As a teacher, I couldn’t be happier.

In just a few weeks, ITU is now the second-largest and second-ranked Danish uni on Kattis. Aarhus is still way ahead.

Future

I would love to make this event even more social and less competitive. An idea that came up during the contest was to have the scoreboard ranked by “most recent solve” rather than “number of solves”. That way, every team gets to be at the top at least once. Removing the scoreboard entirely is another option, but that removes the shared digital forum – in effect, all the teams would exist in their own little bubble.

The best idea we’ve come up with in this vein is to couple the teams with music playlists. Then the current leader (i.e., the team that most recently solved a problem) would decide which music is played in the bar. “Will Code for Drinks and Music” or “Will Code for Drinks and Rick Roll” or something. To make this work, we need a more advanced registration system, and we’d need to scrape the standings off the Kattis server.  All doable.

Another improvement would be to have our own, ITU- or ScrollBar-branded problems instead of relying on (often well-known) problems from the Kattis pool. We could switch to another system than Kattis (or build our own) but that is a lot of work, and there is intrinsic value in incentivising students to register on Kattis.

No matter the form, we will certainly do this again in Spring 2019!

A Glimpse of Algorithmic Fairness

Workshop presentation at Ethical, legal & social consequences of artificial intelligence, Network for Artificial Intelligence and Machine Learning at Lund University (AIML@LU), Lund University, 22 November 2018.

Abstract

Several recent results in algorithms address questions of algorithmic fairness — how can fairness be axiomatised and measured, to which extent can bias in data capture or decision making be identified and remedied, how can different conceptualisations of fairness be aligned, which ones can be simultaneously satisfied. What can be done, and what are the logical and computational limits?

I give a very brief overview of some recent results in the field aimed at an audience assumed to be innocent of algorithmic thinking. The presentation includes a brief description of the location of the field algorithms among other disciplines, and the mindset of algorithmic or computational thinking. The talk includes pretty shapes that move about in order to communicate some intuition about the results, but is otherwise unapologetic about the fact that the arguments are ultimately formal and precise, which is important for addressing fairness in a transparent and accountable fashion.

References

Toon Calders, Sicco Verwer: Three naive Bayes approaches for discrimination-free classification. Data Min. Knowl. Discov. 21(2): 277-292 (2010). [PDF at author web page]

Alexandra Chouldechova. Fair prediction with disparate impact: A study of bias in recidivism prediction instruments. [arXiv 1703.00056]

Cynthia Dwork, Moritz Hardt, Toniann Pitassi, Omer Reingold, Richard S. Zemel:
Fairness through awareness. Innovations in Theoretical Computer Science 2012: 214-226. [arXiv 1104:3913]

Michael Feldman, Sorelle A. Friedler, John Moeller, Carlos Scheidegger, Suresh Venkatasubramanian: Certifying and Removing Disparate Impact. Proceedings of the 21th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, Sydney, NSW, Australia, August 10-13, 2015. [arXiv 1412.3756]

Sorelle A. Friedler, Carlos Scheidegger, Suresh Venkatasubramanian: On the (im)possibility of fairness. [arXiv:1609.07236]

Úrsula Hébert-Johnson, Michael P. Kim, Omer Reingold, Guy N. Rothblum: Multicalibration: Calibration for the (Computationally-Identifiable) Masses. Int. Conf. Machine Learning 2018: 1944-1953. [Proceedings PDF]

Jon M. Kleinberg, Sendhil Mullainathan, Manish Raghavan: Inherent Trade-Offs in the Fair Determination of Risk Scores. Innovations in Theoretical Computer Science 2017: 43:1-43:23. [arXiv 1609:05807]


(The image at the top, the title slide of my presentation, shows a masterpiece of the early Renaissance, Fra Angelico’s The Last Judgement (ca. 1430), illustrating a binary classifier with perfect data access and unlimited computational power.)

Excellence in Teaching, ITU 2018

(I’m really proud about having received ITU’s Excellence in Teaching award for 2018. I am first and foremost a teacher, and view education as my most meaningful task. (It’s also the only thing that I am really good at.) Having my work recognised is immensely satisfying.

 

mads, thore.png

ITU Vice Chancellor Mads Tofte presents the award. 23 September 2018.

Here is the laudation from Vice Chancellor Mads Tofte:

Award for excellence in teaching

Every year, ITU awards a few teachers its Award for Excellence in Teaching. We do so based on what students have said about teachers in their evaluations. It is very difficult to choose, because students say so many positive things about so many different teachers. But we have arrived at the following, one from each of our three departments:

Associate Professor Thore Husfeldt of the Department of Computer Science

During the past year, Thore has been teaching “Algorithm Design”, “Algorithms and Data Structures” and “Foundations of Computing – Algorithms and Data Structures”. Here are some of the things that students write about Thore:

  • Absolute rock star
  • Best lecturer on ITU, hands down
  • Thore makes things, that seemed very complicated when reading the book, seem easy peasy when he explains them at the lectures.
  • Jeg kan godt lide den del af undervisningen, hvor vi ved håndsoprækning skal stemme om, hvilket svar vi tror er rigtigt på et spørgsmål. Typisk gør det, at Thore godt fatter, hvad det er, han skal uddybe.
  • The black board exercises in the lectures are a brilliant break in between the coding and explaining.
  • Very engaged! Obviously very capable and passionate about teaching this subject
  • It is the one class I don’t miss, even if it’s at 8am and that’s because of the quality of the teacher

Superintelligence in SF. Part III: Aftermaths

Part II of a 3-part summary of a 2018 workshop on Superintelligence in SF. See also [Part I: Pathways] and [Part II: Failures].

The third and final part of apocalyptic taxonomy describes the outcome, or aftermath, of the emergence and liberation of artificial superintelligence. The list of scenarios is taken from Tegmark (2018). In my introductory slide I tried to roughly order these scenarios along two axes, depending on the capability of the superintelligence, and the degree of control.

 

Tegmark.001

These scenarios are not clearly delineated, nor are they comprehensive. There is a longer description in Chapter 5 of Tegmark (2018). Another summary is at AI Aftermath Scenarios at the Future of Life Institute blog, where you can also find the results of a survey about which scenario to prefer.


Collapse

Intelligent life on Earth becomes extinct before a superintelligence is ever developed because civilisation brings about its own demise by other means than the AI apocalypse.

Reversion

Society has chosen deliberate technological regression, so as to forever forestall the development of superintelligence. In particular, people have abandoned and outlawed research and development in relevant technologies, including many discoveries from the industrial and digital age, possibly even the scientific method. This decision be in reaction to a previous near-catastrophic experience with such technology.

Turing Police

Superintelligence has not been developed, and societies have strict control mechanisms that prevent research and development into relevant technologies. This may be enforced by a totalitarian state using the police or universal surveillance.

Tegmark’s own label for this scenario is “1984,” which was universally rejected by the workshop.

Egalitarian Utopia

Society includes humans, some of which are technologically modified, and uploads.
The potential conflict arising from productivity differentials between these groups are avoided by abolishing property rights.

Libertarian Utopia

Society includes humans, some of which may be technologically modified, and uploads. Biological life and machine life have segregated into different zones. The economy is almost entirely driven by the fantastically more efficient uploads. Biological humans peacefully coexist with these zones, benefit from trading with machine zones; the economic, technological, and scientific output of humans is irrelevant.

Gatekeeper AI

A single superintelligence has been designed. The value alignment problem has been resolved in the direction that the superintelligence has one single goal: to prevent the second superingelligence, and to interfere as little as possible with human affairs. This scenario differs from the Turing police scenario in the number of superintellinces actually constructed (0 versus 1) and need not be a police state.

Descendants

The superintelligence has come about by a gradual modification of modern humans. Thus, there is no conflict between the factions of “existing biological humans” and “the superintelligence” – the latter is simply the descendant life form of the former. “They” are “we” or rather, “our children.” 21st century homo sapiens is long extinct, voluntarily, just as each generation of parents faces extinction.

Enslaved God

The remaining scenarios all assume a superingelligence of vastly superhuman intellect. They differ in how much humans are “in control.”

In the Enslaved God scenario, the safety problems for developing superintelligence (control, value alignment) have been solved. The superingelligence is a willing, benevolent, and competent servant to its human masters.

Protector God

The superintelligence weilds significant power, but remains friendly and discreet, nudging humanity unnoticably into the right direction without being too obvious about it. Humans retain an illusion of control, their lives remaing challenging and feel meaningful.

Benevolent Dictator

The superintelligence is in control, and openly so. The value alignment problem is solved in humanity’s favour, and the superintelligence ensures human flourishing. People are content and entertained. Their lives are free of hardship or even challenge.

Zookeeper

The omnipotent superintelligence ensures that humans are fed and safe, maybe even healthy. Human lives are comparable to those of zoo animals, they feel unfree, may be enslaved, and are significantly less happy that modern humans.

Conquerors

The superintelligence has not kept humans around. Humanity is extinct and has left no trace.


Oz

Workshop participants quickly observed the large empty space in the lower left corner! In that corner, no superintelligence has been developed, yet the (imagined) superintelligence would be in control.


Other fictional AI tropes are out of scope. In particular the development of indentured mundane artificial intelligences, which may outperform humans in specific cognitive tasks (such as C3P0s language facility or many space ship computers), without otherwise exhibiting superior reasoning skills.