Monthly Archives: March 2015

Second year group project demos

Last Wednesday was the culmination of the second year group projects.  We had an afternoon of demos followed by lightning talks from each group showing off their projects.

Here is a brief summary of the projects that the Queens’ students worked on:

Retail Category Manager:  Tatsiana’s group were given the brief of making it easier for retailers to list their products in online marketplaces like Amazon.  The idea was to auto-categorise a list of products based on keywords in the name and description.  They adopted a neat Bayesian approach which they trained on the products already categorised in the marketplace.  This had a nice effect that if a misclassification occurs it can be manually corrected and then the prior probabilities can be updated to reflect the new knowledge.

Location Based Teaching: Radu and Sid’s project was to build a location tracking system which tracked smart phones using iBeacons.  They then implemented a location-based callback system so that you could be notified of interesting events near-by in the building.  The location system worked by matching fingerprints of visible beacons with a previously created fingerprint map.  They managed to get quite accurate results (within 10 metres) in some parts of the building.  However, in more open spaces the accuracy was less good (sometimes even putting you on the wrong floor).   They built an Android app and a website which worked pretty well.

Sid demonstrating his location-aware Android application to Ramsey.

Sid demonstrating his location-aware Android application to Ramsey.

Building the Matrix:  Katie, Ben and Jamie got to play with two Oculus Rift headsets.  They had to build a distributed multiplayer virtual reality game. A lot of work went into this since they built their whole 3D engine from scratch in C++.  The game was bumper cars.  They had managed to get the latency on the headtracking down really well so when you moved your head the view updated very smoothly.  However, the latency of the game controls was quite a bit bigger – that’s my excuse for why I kept getting bumped off the track.

Ben and Jamie demonstrating their virtual reality game.

Ben and Jamie demonstrating their virtual reality game.

Micro friends video diary: Matt’s project involved automatically summarising video.  Their software automatically generates a short 3 second highlight clip of your video and shares in on a social network that they built.  They used various image processing algorithms (such as face tracking) to try and work out which were the best frames to include.  And they built an entire social networking website for people to share and follow other peoples video clips.

Well done to everyone for successfully delivering your projects on time.

A Friendly Competition

This week, in a session run by Jan, we were split into teams comprising one student from each of the first, second and third years and presented with a series of increasingly difficult problems to solve. There were fantastic prizes such as chocolates, flapjacks and even bottled water available for the winners, the runners up and, well, pretty much everyone.

Three people enter a room, each one with either a blue or a red hat on their head. They do not know the colour of their own hat but they can see the hats of the other two people. Once they had a chance to observe the colour of the other hats, they can guess what colour their hat is or say nothing. All guesses happen simultaneously and no other communication is allowed. if no one guesses wrong and at least one person guesses correctly, they win, otherwise they lose. Given that the colour of each hat is assigned randomly by a flip of a fair coin, what is the best strategy and how often does it win?

The first question was one of probability. Surprisingly unintuitive, perhaps you wouldn’t expect there to be a strategy any better than picking at random, but you’d have to think again. Radu, on my team, got to the answer fairly quickly but it took much longer for him to convince Holly and me that he was correct!

You are given two hourglasses. One measures 4 minutes and the others measures 7. Can you measure 9 minutes?

Bonus: given two hourglasses that measure n and m minutes, what values of k minutes can you measure and how much set up time do you need?

This question is closely related to the perhaps more widely known problem of measuring a specific amount of water given two unmarked jugs that are known to hold n and m litres respectively. You can fill the jugs up, empty them, or transfer water from one jug to the other until one is either full or empty. You can’t, say, pour out half of the water, however: you have no way of measuring exactly half, just as you have no way of knowing when exactly half of the time from one of the hourglasses is up in this problem.

Our team solved the hourglasses question more quickly than the first one, perhaps because all of us had seen the isomorphic water jugs question before.

Given a standard 52 card deck, 5 cards are randomly chosen by a member of the audience and given to a magician. He then selects one of the cards and keeps it, while arranging the remaining four cards on a table face up. A second magician then determines what card the first magician kept. What strategy did they use?

Note that while arranging the cards on the table, only their order can be significant, e.g. you cannot rotate them in any way to give extra information to the second magician.

In this clever question, it appears at first as if you do not have enough bits of information available to communicate which of the remaining 48 cards has been selected. Indeed, our team almost didn’t believe that was possible at first, and not one of the teams present was able to solve the problem after almost twenty minutes of discussion.

Eventually, Jan stepped up to the whiteboard and explained the solution — after a few people left the room, determined to come up with an answer themselves and refusing to have the game given away to them. Even once it had been explained, many of us didn’t see how the solution worked until we had discussed it amongst ourselves for another five minutes!

Following this question, the hour for the meeting was almost over, and besides, the non-muggles among us had to leave to go to a Harry Potter themed formal hall. But the dedicated computer scientists stayed for one final enigma.

You are given 3 Turing Machines and want to determine which ones terminate and which ones don’t. You have access to an Oracle that, given a Turing Machine, tells you whether it terminates or not. However you can only query it twice.

Again, this question seems impossible because you are only given two bits of information and must seemingly use those to distinguish between 8 different possibilities. However, a solid understanding of the theory of computation led Eduard to a brilliant way of generating that final bit that the Oracles cannot themselves provide.