Good Morning All,


6th week is here and the sun is shining. I daresay soon it will be flip flop weather.


This Wednesday we will be having our important Annual General Meeting, during which we will be electing a committee to replace Alex, Ian, Laurens and I. There will be pizza, and potentially hot cross buns. Please note yet another change in venue for this event from our printed term card. We will be on the first floor of St Catherine’s lodge.


Since, yet again, no one correctly solved last week’s technology challenge the prize for whoever solves it this week will be £15. Along with last weeks clue, another is printed below.


Details about the AGM, the technology challenge, an event CoreFiling are running and possibly more are below.


Have a good one,


Ben and Alex

CompSoc Co-Presidents




                      The Oxford Computer Society




CompSoc AGM including elections:

Wednesday 22/02, 6pm, St Catz Arumugan Building First Floor Meadow Facing

FB Event:


Please note the change in venue compared to our printed termcard


Out with the old, in with the new.


We will be reviewing progress the society has made this term and discussing any other issues that arise. Elections for the 2012/2013 committee will be held (further details to be sent on mailing list). If you are interested in standing for a position please get in touch with the committee if you have any questions.


If you are interested in the intricacies of how the AGM/society works then please see the constitution. (


Pizza and drinks will be provided! (and possibly hot cross buns)


The Arumugan building is the fancy name of the lodge, we will be in the room just to the left after you go up the stairs. We’ll put up some signs in the lodge (which is that big glass building straight in front of you as you walk into catz) to the room.


Here is a handy map for finding Catz: If you get truly lost in Catz, you can call Ben on 0754 999 3401.


This event, like most CompSoc events, is free for anyone to attend. Although only members of the society may vote in the meeting.


Specific election information:


If you think you might be interested in a role on the committee then please feel free to get in touch with us over and we'd be happy to answer any questions that you might have – alternatively speak to us in person of course!


Along with the positions required by the university (President, Secretary and Treasurer) a number of other roles could be suitably created, such as Vice President, Social Secretary, Sponsorship Secretary, Publications Officer, etc. (basically whatever title + support that you think could be provided to the society). Personally, I (Ben) believe that a larger committee than the required roles is highly preferable – there is an upper limit of 10 members to the committee. Constitutionally, we have the that the required positions are:


The President, to preside over meetings, to authorise all expenditure and ultimately be responsible for the running of the Society.

The Secretary, to take minutes at meetings, deal with Society correspondence and stand in for the President when necessary.

The Treasurer, to maintain the accounts of the Society, report to the members thereon, and to stand in for the Secretary when necessary.


The elections themselves will proceed as follows. Initially nominations for President will be asked for, candidate(s) will then give a few words in proposition, questions may be asked to the candidate(s), and then a secret ballot (everyone at the meeting (who is a member) writes down their vote on paper) will be held to determine the winner by simple majority (not counting abstentions). The same will then follow for Secretary and Treasurer. Following this any other positions can be nominated and voted on.


To be nominated you must be proposed by another member, and then seconded by another different member – you must also be a member. You may stand for as many roles as you like, although once you have been appointed to one you cannot stand for another. You may propose or second as many other members as you like (but only 1 per position). For each position you may vote to abstain from voting.


If you are considering standing and need a proposer/seconder feel free to get in touch with as we would be happy to support any candidates looking to stand.




CoreFiling Drinks:


Local software company CoreFiling is hosting an informal get-together at

The Red Lion pub on Thursday 23rd February. Members of the development

team will be on hand to talk to students considering careers in the

software industry and to discuss the opportunities for internships and

full time positions available at CoreFiling. Are you  interested in

working with Java, Python, XML and Linux? Curious about Extreme

Programming and Test Driven Development? Want to know how international

software projects are managed?  If so then come along for a chat over a

drink or two to find out more.


Drinks and snacks will be provided. No need to book.


Date: Thursday 23rd February (6th week)

Time: 5.30pm - 8.30pm.

Location: Red Lion Pub, Gloucester Green.




Technology Competition:

Challenge 6:


A discrete elevator simulation.


This challenge is using a given list of discrete elevator request events (found at determine the number of elevators required to service the requests, and their final configuration once the requests have been serviced. The number of elevators required is the minimum needed to ensure all requests are serviced within 21 time blocks (ie completed in 21 or fewer time blocks after creation).


In the file of event requests, an event is either “SKIP”, or a list of requests in the form “x to y;”. “SKIP” is the event where no request was made. “x to y;” is the request go from floor x to floor y. Each line corresponds to the a time block, ie line 0 = time 0, line 1 = time 1 etc. In a single time block the requests for that block are made, then the elevators move in the direction they are travelling in, then the elevators service any requests at the floor they are now at. If an elevator is empty it can enter travel mode, where it will travel towards a selected request with the intention of servicing specifically that request (it can service others as long as they do not want to go past the selected request), as soon as it has picked up the specific request it travels in the direction needed for that request and resumes normal mode.


An elevator can only move up 1 floor, down 1 floor or remain at the same floor during each time block.


There is a building containing elevators which is 10 stories high, with each floor numbered 0 through to 9 (ie. 0 is the ground floor). Users request the elevator by pushing a button on the floor they are currently at, indicating the floor they are going to.


An elevator’s initial configuration is that it is idling at level 0. Individual elevators follow the following protocol:


Elevators can be in 2 modes: Normal mode and Travel mode

Normal mode:

1 currentFloor = currentFloor + direction //as long as this won’t place the elevator out of the building

2 let people out of the elevator if they are in it and this is their floor

3 if no one is in the elevator, then direction = 0 //ie we are idling

4 if anyone is waiting at currentFloor and would like to travel in the same direction as the elevator (or the elevator is idling) then they get on and we go to the floor they requested, if we were idling then we go in the direction for that floor. We always let the people who have been waiting the longest on first.


Travel mode:

1 currentFloor = currentFloor + direction //as long as this won’t place the elevator out of the building

2 let people out of the elevator if they are in it and this is their floor

3 if anyone is waiting at currentFloor and would like to travel between targetFloor and currentFloor then they get on

4 if currentFloor = targetFloor then let anyone on who would like to go in targetDestination direction and set direction to be towards targetDestination

5 switch to Normal mode


An elevator will switch into Travel mode if at the end of part 4 of normal mode it does not contain any passengers. When it switches into travel mode, it will take a request (x to y) which isn’t being acted upon by another elevator and travel to targetFloor (x), doing as much transporting as it can on the way, then will travel towards targetDestination (y). When it is travelling towards targetDestination it has switched back into Normal mode.


If there are [0..N] elevators the system acts in the following manner:

1 todo = <read in request events happening on this time block (if there are any)>

2 for i = 0 to N do

3    execute elevator i’s protocol once, removing any request events from todo which it can immediately handle

4 for i = 0 to N do

5    if elevator i is in Normal mode and empty, and todo is not empty then

6          take the request which has been waiting longest (x to y) from todo, and switch elevator i into Travel mode with targetFloor = x and targetDestination = y

7 advance the time by 1 and go back to step 1


One request is determined to be waiting longer than another if it was generated before the other. If they were generated at the same time, then the request before the other in the list defining them in the requests.txt file is the one that has been waiting longer.


Answers can be submitted to<num of elevators><final floor of elevator 0><final floor of elevator 1><etc..> (obviously without the brackets, ie just a string of numbers). Whilst the solution to this challenge may seem to favour using methods taught in 2nd year CompSci, it can clearly be solved without using any of that fanciness.


An example runthrough and solution can be found at


As a clue to help you solve it, 6 elevators are required to service all of the requests in time. A second clue is that none of the lifts end up in positions 0, 2, 4, 6 or 9.


Anyone (with a email address) can sign up to the competition through the website, but only members can receive prizes. isn't connected to the compsoc network, and so you will need to make a new account to participate.


For more details about the competition see or contact if you have questions about this round.




Technology Competition:

Week 5 result:


No one solved the challenge!




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