Education, Life

All Shall Be Well

You step in the stream,
But the water has moved on.
This page is not here.
-- Internet Folkore

Rather surprisingly even for me, it has already been over five months since my last post. Writing a thorough and yet succinct account about everything that happened over that time is way beyond my literary abilities, so here's a bullet-point summary about a few things worth mentioning from that period.

1. Cambridge CST Part IB Exams

Back in June 2012, folks at Computer Science Tripos Part IB (including me) had the opportunity to enjoy four consecutive days of exams. The structure of papers was straightforward: three hours, nine questions (one or two questions per course); five questions had to be answered.

University of Cambridge, Jennings Prize

Jennings Prize '11

If I could give a single advice to someone who is about to go through this process, it would be "focus on the time". Three hours will not be enough to answer five questions, and there will be almost no time to think about anything if you get stuck. Most likely, the bottleneck in your answers will be the speed of your writing, so don't make a huge mistake by thinking that you will be able to do less revision and figure out things "on the spot". You won't.

At the end of the day, of course, it's not the grades that matter, but... receiving the thing on the left was still nice.

2. Internship at Microsoft

My office at Microsoft

My office at Microsoft (Redmond, WA, 2011)

After three days from my last exam I arrived to my office at Microsoft, in Redmond, WA.

Over the summer, I was working as a Software Development Engineer in Test in Microsoft Office team. In particular, I was writing a performance testing suite for the feature that is used across Office and Windows divisions when developing and updating over 50k+ pages of documentation on MSDN.

Microsoft Campus, Redmond, WA, 2011

Microsoft Campus

Well, I say "working". The summer was literally packed with events for interns! Starting with the intern day of caring, when we spent a full working day volunteering for the community, and ending with the huge intern celebration involving Dave Matthews and customized Xbox + Kinect bundles for everyone!

And then, there were meetings and talks by senior people in the company. And by senior people, I don't mean my manager's manager. Just to throw in a few names, we heard talks from Andy Lees, Steven Sinofsky and, of course, Steve Ballmer (or as he's known within the company, SteveB).

Seattle Skyline, WA, 2011

Seattle Skyline, WA, 2011

I even had a half-an-hour chat with the head of the Microsoft Office Division, Kurt DelBene - definitely one of my best experiences over the whole internship!

Also, the perks that you get as an intern are incredible: paid flights, subsidized housing, free bike, two weeks of free rental car, gym plan (and if you're around Redmond, WA area - check out the Pro Sports Club). That, and all-you-can-drink soda at work! (OK, so you don't get free food as in some other places, but trust me, you will able to afford food from your intern compensation package).

With Coworkers at Vancouver, BC, Canada, 2011

Vancouver, BC, Canada

Finally, there are people that you are working with. If you are as lucky as me, then everyone's going to be exceptionally smart, and nevertheless, extremely approachable. I wouldn't have achieved anything over this summer if not for my team; their help and guidance was invaluable. And not only limited to the working environment - the weekend trip to Vancouver, BC was pretty epic, and I already miss our regular Friday basketball games, just outside the office.

However, to make things even better, I have already received an offer for the summer of 2012! If there aren't any major changes, there is a good chance that I will spend my next summer working as a Program Manager intern at Microsoft Office team!

Microsoft Campus, Redmond, WA, 2011

Microsoft Campus (Redmond, WA, 2011)

3. Vacation

This year me and Ada have decided to go to Turkey. We have spent two final weeks of September in a beautiful Alanya region: the weather (every single day above 30°C/86°F) justified the nickname of the region ("Where The Sun Smiles") and the Mediterranean Sea was simply magnificent. We were also very lucky with the choice of the hotel: two pools, five minutes away from the sea, extremely polite and courteous staff, and great all inclusive food and drinks!

Anyway, a picture is worth more than a thousand words, so here's a few of them. Enjoy!

P.S. Fact: it is possible to get a 500% discount when buying a leather jacket in Turkey. Verified. And it takes only a little bit over two hours of negotiating.

162 Kudos
Development, Education

Backpropagation Tutorial

The PhD thesis of Paul J. Werbos at Harvard in 1974 described backpropagation as a method of teaching feed-forward artificial neural networks (ANNs). In the words of Wikipedia, it lead to a "rennaisance" in the ANN research in 1980s.

As we will see later, it is an extremely straightforward technique, yet most of the tutorials online seem to skip a fair amount of details. Here's a simple (yet still thorough and mathematical) tutorial of how backpropagation works from the ground-up; together with a couple of example applets. Feel free to play with them (and watch the videos) to get a better understanding of the methods described below!

Training a single perceptron

Training a multilayer neural network

1. Background

To start with, imagine that you have gathered some empirical data relevant to the situation that you are trying to predict - be it fluctuations in the stock market, chances that a tumour is benign, likelihood that the picture that you are seeing is a face or (like in the applets above) the coordinates of red and blue points.

We will call this data training examples and we will describe ith training example as a tuple (\vec{x_i}, y_i), where \vec{x_i} \in \mathbb{R}^n is a vector of inputs and y_i \in \mathbb{R} is the observed output.

Ideally, our neural network should output y_i when given \vec{x_i} as an input. In case that does not always happen, let's define the error measure as a simple squared distance between the actual observed output and the prediction of the neural network: E := \sum_i (h(\vec{x_i}) - y_i)^2, where h(\vec{x_i}) is the output of the network.

2. Perceptrons (building-blocks)

The simplest classifiers out of which we will build our neural network are perceptrons (fancy name thanks to Frank Rosenblatt). In reality, a perceptron is a plain-vanilla linear classifier which takes a number of inputs a_1, ..., a_n, scales them using some weights w_1, ..., w_n, adds them all up (together with some bias b) and feeds everything through an activation function \sigma \in \mathbb{R} \rightarrow \mathbb{R}.

A picture is worth a thousand equations:

Perceptron (linear classifier)

Perceptron (linear classifier)

To slightly simplify the equations, define w_0 := b and a_0 := 1. Then the behaviour of the perceptron can be described as \sigma(\vec{a} \cdot \vec{w}), where \vec{a} := (a_0, a_1, ..., a_n) and \vec{w} := (w_0, w_1, ..., w_n).

To complete our definition, here are a few examples of typical activation functions:

  • sigmoid: \sigma(x) = \frac{1}{1 + \exp(-x)},
  • hyperbolic tangent: \sigma(x) = \tanh(x),
  • plain linear \sigma(x) = x and so on.

Now we can finally start building neural networks. Continue reading

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Development, Education, Life

Halfway There

Another term in Cambridge has gone by - four out of nine to go. In the meantime, here's a quick update of what I've been up to in the past few months.

1. Microsoft internship

Redmond, WA, 2011

Redmond, WA, 2011

In January I had the opportunity to visit Microsoft's headquarters in Redmond, WA, to interview for the Software Development Engineer in Test intern position in the Office team. In short - a great trip, in every aspect.

I left London Heathrow on January 11th, 2:20 PM and landed in Seattle Tacoma at 4:10 PM (I suspect that there might have been a few time zones in between those two points). I arrived in Mariott Redmond roughly an hour later, which meant that because of my anti-jetlag technique ("do not go to bed until 10-11 PM in the new timezone no matter what") I had a few hours to kill. Ample time to unpack, grab a dinner in Mariott's restaurant and go for a short stroll around Redmond before going to sleep.

On the next day I had four interviews arranged. The interviews themselves were absolutely stress-free, it felt more like a chance to meet and have a chat with some properly smart (and down-to-earth) folks.

Top of the Space Needle. Seattle, WA, 2011

Top of the Space Needle. Seattle, WA, 2011

The structure of the interviews seemed fairly typical: each interview consisted of some algorithm/data structure problems, a short discussion about the past experience and the opportunity to ask questions (obviously a great chance to learn more about the team/company/company culture, etc). Since this was my third round of summer internship applications (I have worked as a software engineer for Wolfson Microelectronics in '09 and Morgan Stanley in '10), everything made sense and was pretty much what I expected.

My trip ended with a quick visit to Seattle on the next day: a few pictures of the Space Needle, a cup of Seattle's Best Coffee and there I was on my flight back to London, having spent $0.00 (yeap, Microsoft paid for everything - flights, hotel, meals, taxis, etc). Even so, the best thing about Microsoft definitely seemed to be the people working there; since I have received and accepted the offer, we'll see if my opinion remains unchanged after this summer!

2. Lent term v2.0

Well, things are still picking up the speed. Seven courses with twenty-eight supervisions in under two months, plus managing a group project (crowd-sourcing mobile network signal strength), a few basketball practices each week on top of that and you'll see a reason why this blog has not been updated for a couple of months.

It's not all doom and gloom, of course. Courses themselves are great, lecturers make some decently convoluted material understandable in minutes and an occasional formal hall (e.g. below) also helps.

All in all, my opinion, that Cambridge provides a great opportunity to learn a huge amount of material in a very short timeframe, remains unchanged.

There will be more to come about some cool things that I've learnt in separate posts, but now speaking of learning - it's revision time... :-)

Me and Ada at the CompSci formal. Cambridge, England, 2011

Me and Ada at the CompSci formal hall. Cambridge, England, 2011

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Development, Life

Morgan Stanley Internship

After work (Canary Wharf, 2010)

After work (Canary Wharf, 2010)

Last week I received a short e-mail from my former manager at Morgan Stanley:

"Hi Manfred,

Just to let you know that GlobalAxe all went live last week and so far no issues at all."

Since the people on the trading floor started using my system and it seems to be standing on its feet so far, it probably is a good time to recap on what had happened over my ten week internship at Morgan Stanley.

I was working as technology analyst in repo trading team (in institutional securities group). My task was to develop and integrate a new screen into trading software, to create an associated e-mail subsystem generating daily/weekly reports for senior executives and to code a website which would provide access to the data for executives/sales people without the trading software on their machines.

Development-wise it involved working with quite a wide range of technologies, such as C# and CAB for UI development, Java/Spring for e-mail report generation/server backend, MVC under ASP.NET for the website, Transact-SQL for Sybase DB backend; everything interconnected with SOAP/XML and distributed locally over in-house pubsub systems or through IBM's MQ for inter-continental data transactions.

Even though working and learning about all these technologies was fun on it's own right, the best thing I would say about my experience was the people.

Night at Canary Wharf, 2010

Night at Canary Wharf, 2010

There is no better feeling than having a quick call with traders in New York demoing them the stuff that you just wrote, then dropping an e-mail to Tokyo checking if your recent changes made it through to their database, discussing the architecture of your system with the guys in your team and then going to the global team video-meeting; all in the same day.

And sometimes you feel the need to pinch yourself, because the level of responsibility that you get as an intern is staggering. You have the same rights and responsibilities as any other team member: a screw up in your code can block sixty people from submitting their code before the end of the iteration, a failure to convince the head of traders in NY that what you are doing is going to help them will affect the name of the whole team, and so on.

But then, you own your project: you make the final design decisions, you implement it and you give it to the end-users, who often appear to be bigshots. And that more than makes up for a few late nights in the office. Plus, Canary Wharf is absolutely beautiful at night.

Without expanding too much (and breaching too many non-disclosure agreements) - it was definitely the best experience so far: in terms of team, project, technology, skill, involvement and everything else. And it seems like I will have a chance to repeat it again: I have already received an unconditional offer for the internship at MS next summer!

Oh, and regarding the summer days spent in glass, steel and stone towers... well, Majorca more than made up for it!

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CST Part 1A

... otherwise known as Part 1A of Computer Science Tripos in University of Cambridge has officially ended.

All in all, a rather enjoyable year. From the introduction to ML by the brilliant Prof. Larry Paulson, to the realms of Discrete Mathematics II (with a wicked a proof of existance of ordinal numbers in the exam); from Algorithms to Software Design, from Digital Electronics to Operating Systems, from Floating-Point Computation to Regular Languages and Finite Automata; and everything in between.

A crash course, but the one that is definitely worth going through.

If you're just about to come to Cambridge (or just starting your part 1A), here are a few simple tips that proved to be helpful for me:

  • Don't fall behind - in lectures, ticks, homeworks, supervision assignments - in Cambridge pace it's difficult to catch up.
  • Do things in advance - it's usually a very good idea and pays off well.
  • Make sure that you keep your work/life balance: do a bit of sports (many choices in University of Cambridge Societies website) and go out once in a while. Paradoxically, having a few hours off in a week will help you to stay on top of things.
  • Finally, keep an eye on these subjects: Discrete Mathematics II, Operating Systems II, Floating-Point Computation, HW ticks (sorted by the effort they took from me, in decreasing order). They might be different for you, but these particular ones are worth being aware of.

But most importantly - enjoy what you're doing.
Good luck and have fun.

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Education, Life, Music

"The Hard Way is the Right Way"

While the Europe is paralyzed by the volcanic ash and I am restrained from coming back to Cambridge, here is a quick recap of what I have been doing for the past couple of months.

1. Guitar

It looks like it is becoming a tradition - another vacation ends with a guitar video. This time - a short slow blues in Stefan Grossman's style. The usual apologies for the sound, video and playing quality apply.

Slow blues in E (Sefan Grossman's style).

2. Professional

The Chartered Institute for IT
I was accepted as a student member to the Chartered Institute for IT (former British Computer Society). For the next two years (at least) I should be reachable through this e-mail:

3. Studies

Without getting into the gory details, the outcomes of the Lent (read: second) term in Cambridge can be summarized by:

Mandelbrot Set

Mandelbrot set (1280x1024)

  1. a wallpaper "spit out" by ML depicting a rather standard Mandelbrot set fractal (on the right),
  2. an animation "spit out" by Java depicting eight-hundred generations of the spacefiller pattern in the Conway's Game of Life (further on the right),
  3. and an insane amount of material to prepare for the upcoming exams; both broad and not as shallow as I expected.

I am still extremely enjoying it, even though the amount of my spare-time has decreased. (As an afterthought - I still had time to play basketball for Blues, Lions and my college, so maybe it was not that bad).

4. Internship

Over the summer I will be working as a Technology Analyst for Morgan Stanley, in their Innovative Data, Environments, Analytics & Systems (IDEAS) group.

During the interviews Morgan Stanley really left a very good impression both at the level of knowledge of the people working there and the communication and culture inside the company. We will see if that applies in day-to-day situations. In any case, I have nothing against spending the summer in Canary Wharf and seeing the investment banking industry from inside.

It will surely give me more things to write about in this blog, so be sure to check back once in a while.

Internship Offer Packs from Morgan Stanley and Citigroup

Competition: internship offer packs from Morgan Stanley and Citigroup.

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Development, Education

Conway's Game of Life

1. Description

In 1970s John Horton Conway (British mathematician and University of Cambridge graduate) opened a whole new field of mathematical research by publishing a revolutionary paper on the cellular automaton called the Game of Life. Suffice it to say that the game which he has described with four simple rules has the power of a universal Turing machine, i.e. anything that can be computed algorithmically can be computed within Conway's Game of Life (outlines of a proof for given by Berlekamp et al; implemented by Chapman as a universal register machine within the Game of Life in 2002).

Launch the Game of Life...

Glider in the Game of Life

The Game of Life is a zero-player game, i.e. the player interacts only by creating an initial configuration on a two-dimensional grid of square cells and then observing how it evolves. Every new generation of cells (which can be either live or dead) is a pure function of the previous generation and is described by this set of rules:

  1. Any live cell with fewer than two live neighbours dies, as if caused by underpopulation.
  2. Any live cell with more than three live neighbours dies, as if by overcrowding.
  3. Any live cell with two or three live neighbours lives on to the next generation.
  4. Any dead cell with exactly three live neighbours becomes a live cell.

For more information, patterns and current news about the research involving Game of Life check out the brilliant LifeWiki at

2. Implementation

The following applet visualising the Game of Life has been developed as part of the coursework for Object-Oriented Programming at the University of Cambridge, all code was written and compiled in Sun's Java SE 1.6.

Click on any of the screenshots or the button below to launch the Game of Life (and if nothing shows up, make sure that you have the Java Runtime Environment (JRE) installed).

Game of Life Implementation by Manfredas Zabarauskas

Spacefiller (Game of Life applet)

Continue reading

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Education, Life, Music

Unplugged in G

Another vacation, another video - as usual, apologies for the sound, webcam and playing quality. Three days left 'till the journey back to Cambridge.

Gel electrophoresis of Senecio vulgaris, S. squalidus and S. cambrensis DNA strands.

Gel electrophoresis of Senecio vulgaris, S. squalidus and S. cambrensis DNA strands.

Vacation status: haven't even touched anything related to Computer Science. On the other hand, brushed up on complex trigonometry/logarithms and series expansions (read: maths), and feel reasonably happy to discuss plant evolution through polyploidy (read: biology, see: picture on the right).

Post-vacation status update: apparently I did have to discuss plant evolution through polyploidy in my exam! What were the odds...

Anyway, here's the video. Oh, yes, and while we're at it - happy New Year to you all.

Eric Clapton - Wonderful Tonight (0:00/3:50),
Guns N' Roses - Wild Horses (3:54/6:16).

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Development, Education, Life

It Literally Pays Off to Do Homework in Cambridge

Well done! - joint shortest traditional (and practical :-) sort for the OS1a prize tick.

"Well done! - joint shortest traditional (and practical :-) sort for the OS1a prize tick". Cambridge, 2009.

45 minutes, 28 MIPS instructions and £25.
Computer Science FTW.

# Copyright Manfredas Zabarauskas, 2009.
# MIPS routine that reads an array of ten integers 
# and prints the sorted array to console.
main:   sub $t7, $sp, 40
l_read: li $v0, 5
        sw $v0, 0($t7)
        add $t7, $t7, 4
        bne $t7, $sp, l_read
l_out:  sub $t8, $sp, 36
        sub $t7, 40
l_inn:  add $t8, $t8, 4
        lw $t2, -8($t8)
        lw $t3, -4($t8)
        ble $t2, $t3, no_swp
        sw $t2, -4($t8)
        sw $t3, -8($t8)
        move $t7, $sp
no_swp: bne $t8, $sp, l_inn
        beq $t7, $sp, l_out
l_prnt: li $v0, 11
        li $a0, 10
        li $v0, 1
        lw $a0, 0($t7)
        add $t7, $t7, 4
        bne $t7, $sp, l_prnt
        li $v0, 10


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