In Love With Computer Science

There's a nice article written by a senior lecturer of UCSC, Dr. Chamath Keppitiyagama about the Turing Machine. I really like that article since I'm a big fan of theoretical computer science. It is a good attempt to show up an important concept to the ordinary people. I thought to repost it's content here to make it secure so that if the original article goes off, I won't miss it. :)

Link to original article: http://www.nation.lk/edition/component/k2/item/3666-a-computer-for-hundred-rupees?.html

A computer for hundred rupees?

No, I did not miss by several zeros – I meant it. We can build such a cheap computer and I guarantee that it can solve any problem that can be solved by those fancy and expensive computers. Now do not rush to buy processors, power supplies and other equipments, because we do not need them!

You can get the following ‘parts’ under hundred rupees. You need a long paper tape (a very long one), a pencil, an eraser, and a note pad. Take the long paper tape and using the pencil draw equal-sized squares along the tape.

That is it. Now there are some rules to follow. You can move the tape one square to the left or one to the right. You can write ‘1’ or ‘0’ on the square directly under your hand. If you wish you can erase anything on the square directly under your hand. After taking any action you can write a number in the note pad to indicate your ‘state’. The note pad has a table that you can consult before taking any action. This table tells you what to do – write, erase, move left or right – when you are in a given state and after reading a particular value from the tape. All that you can do is limited to those few actions.

That is your 100 rupee computer. I am not joking, but this machine is so powerful that it can solve any problem that can be solved on fancy computer. In fact, if a problem can be solved using a computing device, this computer can solve it. If this computer cannot solve a problem then it can never be solved using even a super computer. Unbelievable, isn’t it? Yet, it is true.

This machine is called a Turing machine. It was designed by Alan Turing in 1936, quite a long time before anybody made a computing device that resembles modern day computers. He did not propose it as a machine to be built and used for actual computation, even though you can easily build one if you really want to and use it for computation. Alan Turing proposed the Turing machine as a model of computation. He proposed that if any problem can be solved using computers this extremely simple machine can solve it and only the problems that can be computed on this machine can be solved on computers. It makes our 100 rupee computer a very powerful one indeed!

I have simplified the description of the machine quite a bit. A Turing machine needs an infinitely long tape, but let us ignore those details. Initially, the problem to be solved is written on the tape using ones and zeros on the squares (strictly speaking they do not even have to be ones and zeros, they can be any symbols). When the machine stops – that is when you stop moving the tape back and forth – the answer will be on the tape encoded in ones and zeros.

Computer scientists and mathematicians use this simple machine to study whether problems can be solved on computers and if so what are the most efficient ways to solve them. They do not actually build the machine, but use it to think of computing as a sequence of those actions allowed in the Turing machine. Even though they look very complicated, modern day computers try to mimic this machine. The role that you played in our 100 rupee computer is played by the processor and the memory chips take the place of the paper tape. The electronic processor is just faster than you and the problems can be solved faster, but apart from the speed, modern computers are not more powerful than a Turing machine. In fact, they are less powerful since none of them have an infinite memory whereas the Turing machine has an infinitely long tape (memory).

The power of this simple machine does not stop there. I am sure you have heard of those wonderful programming languages such as Java, C# and Python. Those programming languages are no more powerful than the simple set of instructions on our rudimentary computer. If you can write a nice program using those languages, you can write the same one using our simple set of instructions, but that would be tedious. Most of us have the notion that computers are all powerful devices. Well they are in some ways, but so is our Turing machine! I am sure now you have lost your faith in computers.

(The writer is a Senior Lecturer, University of Colombo School of  Computing)

Gnuplot For Visualizing Data

When writing research papers and technical documents, displaying data in a useful manner is really important. Specially when presenting different evaluation results in a statistical form in documents we  need to draw different types of graphs. Since it is important to me, I was looking for a good tool for that for sometime. Since I'm using Ubuntu Linux, the best recommended one I could find on the Internet was Gnuplot. It's a free tool and very powerful to draw different types of graphs.

Since it is a command line tool it takes some time to learn about how to use Gnuplot for our requirements. Therefore I postponed my Gnuplot learning process several times and finally today I got some first hand experience. At first I found this blog post. Then it sent me to this tutorial which contained so many helpful information. I recommend it if you really want to learn to use Gnuplot tool from the beginning.

To make my mind easy to memorise what I have learnt up to now, I decided to write a little summary of the basic things I need to use Gnuplot. So, here we go.

 1. To install gnuplot on my Ubuntu-11.04 system, I issued the following command in the terminal.

         sudo apt-get install gnuplot-x11

2. No I can start gnuplot by issuing the following command.

    gnuplot

It will show a prompt like the one showed in the above picture and all the other thing has to be done on this prompt. If you want to exit from the gnuplot, type 'exit' on the prompt.

3. Now let's create an example plot and write it in to an image file. To do that issue the following commands on the prompt.

    set terminal jpeg 

    set output 'our_file_name.jpg'

    plot sin(x)

Now in a new terminal you can go to the working directory of the gnuplot and open the 'our_file_name.jpg' file to view your graph. You can find out the working directory of gnuplot by typing 'pwd' on the prompt just like you do in normal terminal. To change the working directory use 'cd' as follows on the prompt.

cd "/path/to/new/directory"

4. To add the names of the graph, the x axis and the y axis use the following commands.

         set title "My graph title"

    set xlabel 'x axis'

    set ylabel 'y axis'

After changing these settings we have to re-run the previous plot command with new changes. We can do it in shorten way by using 'replot' command as below so that you don't have to write a plot command again and again since sometimes plot command is too long with so many parameters.

    set terminal jpeg

    set output 'plot.jpg'

    replot

5. Even though we set different parameters in gnuplot as above, they are gone if we exit from gnuplot and start it again later. Therefore it's useful to save current configurations so that we can load them again.

View the current configuration by issuing the following command.

    show all

You can save the configuration to a file as below.

     save "savefile.plt"

You can load a saved configuration from a file by the following command

      load "savefile.plt"

6. Now we want to draw a graph using the data which comes from another data file. Consider the following file named 'my_data.dat'.

 1 10 11   
 2 20 23   
 3 30 34   
 4 40 45   
 5 50 56   
 6 60 67        
 7 70 78   
 8 80 89   
 9 90 100  

We have three columns of data in that file. Let's draw a graph with first two columns.

      set terminal jpeg
     set output 'first_graph.jpg'
     plot "./my_data.dat" using 1:2 title "First line" with lines

first_graph.jpg

Now let's draw two graphs in the same figure. The first graph use first column as x-axis and second column as y-axis while the second graph use the first column as x-axis and third column as y-axis. Here's how we do that. 

     set terminal jpeg
     set output 'second_graph.jpg'
     plot "./my_data.dat" using 1:2 title "First line" with lines, "./my_data.dat" using 1:3 title "Second line" with lines

second_graph.jpg

There are so many other things to learn in Gnuplot to create nice graphs. I believe that learning gnupot would not be a wastage of time since good data visualisation is an important skill which should be in a computer scientist. So, I should expertise it in the future.  :)

That's all for now. Enjoy drawing graphs with gnuplot!

Moving Into an Important Time

I couldn't write something useful here for a considerable time. Even though I'm really busy on my final year project works I was unhappy about leaving my blog without writing something. I'm writing this post to make my mind although there's nothing useful in it.

Currently I'm in a crucial time period in my final year project. The designing phase went without any pain but now I'm facing so many issues from the beginning of implementation phase. So, for about a month I had a huge pressure in my head. But I think now most of those issues are solved to a considerable extent and therefore I hope to move in a straightforward process. That's about my project.

EasyPic Board (thanks to Chathika for the picture)

In this semester I'm taking the Robotics & Embedded Systems course and therefore I have to work with electronic stuff. Even though I'm working closely with embedded platforms from a longer time in Wireless Sensor Networks research work, I hadn't step into much lower hardware level. In this semester with this new course I think I will earn the necessary skills in electronics that I was lacking for years.

There's another important thing we have ahead. It's the ICTer 2012 conference. International Conference on Advances in ICT for Emerging Regions (ICTer) is mainly organised by our university with so many partners. As the SCoRe research group we hope to submit a paper to it. So, currently we are completing the paper writing task these days. The call for papers notice can be found here.

So, in every aspect it's a busy time. But I will try my best to keep my blog alive since this is the place which allows me to write anything I like.

A good tool for designing research posters

Recently I had to design a poster for a conference. I was thinking about which tool to use for it. One of a researcher on our lab suggested me to use a free and open source tool called Scribus. I hadn't used it before but found that it is really helpful for designing the poster. 

Even though I'm not good at designing posters like stuff, I had to put a big effort to come up with my poster. Following image shows how it finally looked. It may not have been designed considering all the Do's and Dont's  of designing academic posters since I hadn't enough time to worry about them.

I hope Scribus will be the tool for me to prepare posters for a long time from now on.

Science and Music all together - The Symphony of Science

Recently I found a very nice website called The Symphony of Science which contains an excellent set of music with the voices of so many great people. I downloaded some of the music videos and they are really inspiring.

I would like to share two of those music videos which are my favorites.

Nice Diagrams For A Research Paper or Thesis

Until recent time I have been using Inkscape to draw technical diagrams for different documents and articles I write. However now I think I have found the best tool for such tasks. DIA is a diagram creation program which is inspired by Microsoft Visio. DIA is the perfect tool for preparing very high quality sketches for technical documents.

Since most of the time I use Latex to prepare my documents, I need all the diagrams and graphics in special formats that can be included in Latex documents. For example When preparing research papers using Latex templates most of the times I had to convert my images and documents to EPS file format since the Latex template for the particular conference or journal needs the graphics in that format. What I used to do in such situations is to convert the images and diagrams using an on-line file converter to the EPS format. DIA tool supports so may file formats so that we can export our diagrams to any of them.

DIA can be installed using the software center or otherwise using the command line by issuing the following command.

sudo apt-get install dia


Enjoy preparing quality diagrams for your research papers and technical documents!

The End of a Wonderful Semester - Lessons Learned

           "The dream is not what you see in sleep,
                 dream is which does not let you sleep"
                                                        - Dr. Abdul Kalam

Last Friday, we finished our first semester of the fourth year. Now what we are going to face is the semester end exam. When I start my fourth year after studying for three years in the university, I had been holding a huge collection of experiences and memories in my mind. With all those things, I looked ahead about the fourth year as a totally different time period and I expected something different.


    At the end of this semester when I think back about past few months starting from the October of last year, I wonder how much a fantastic time it was. Unlike all the other semesters, we had a common word in our mouth all the time which is research. In my point of view, the core of the 4th year is the main research project that we have to do throughout the year. Identifying an interesting research problem, reading deeply about the related research works done on that domain and taking initial steps to find a solution can be considered as the main tasks that have to be done during the first semester according to my understanding.


    Unlike the other years, we began to create a closer relationship with the academic staff specially with the supervisors of our research projects. I have two supervisors in my research. They are Dr.Jeevani Gunathileka and Dr.Kasun De Zoysa. Their guidance have helped me to correct the way I work on my project up to now.

    In addition to the research project, I had five more course modules to follow in this semester. Two of them namely "Research Methods" and "Research Seminar" are mandatory courses. If I talk about the "Research Methods" course conducted by Dr.Ruwan Weerasignha, I would say it is a course which helped me to look at the world in a totally different angle. Some of the lectures he did around the topic "Towards a philosophy of Computer Science" led me to read a lot on philosophical texts regarding that. I never thought that philosophy would be such an interesting thing to read without becoming boring. I'm so sure that I will continue to read more on philosophy in the rest of my life time because of the influence I received in this semester.

     The other mandatory course we had is the fantastic "Research Seminar" series. In each week we discuss about two research papers presented by two participants. These research papers are belong to various domains of Computer Science and therefore it increases the breadth of our knowledge while our individual research project increase the depth of our knowledge in a specific research area. Our lecturer Mr. Dulan Wathugala do a great job on throwing us on to the research ocean and help to learn how to survive there.

    Except for few occasions, I never let the paper presenters an easy life at the research seminars. We had lots of arguments and big discussions regarding the papers and their solutions presented for various problems. I can honestly say that I significantly improved my questioning ability by attending to the research seminars. This is the semester I talked a lot. My voice was there in every major discussion and argument. The good news is Research Seminar series will be continued in the next semester also.

    It is not just the academic stuff that made this semester fascinating. We organized our last function in the undergraduate life with a great effort and at the same time with a great fun. It is the Going Down 2012 party we organized for our seniors. Since a big portion of our 2007/2008 batch is in the software industry because of they passed out from the university after completing the three year degree, most of the decoration works and responsibilities had to be handled by the 4th year students who are the remaining part of the batch 2007/2008 inside university. I personally enjoyed all the works we carried out in the preparation for the party. Even in the party day, I enjoyed a lot and danced as much as I wanted in the DJ. It was a fantastic time.

    It is not true if I say it was happiness and joy always around me in this semester. I had so many challenges, difficulties and struggles parallel to the happiness and joy. I could get through all those life experiences with the great helps of all the awesome people around me who never let me go down.
   
    At the last "Research Methods" lecture on last Friday, Dr.Ruwan invited Dr.Shiromi Arunathileka to conduct that last lecture. At the end of her lecture she expressed about her life experiences and difficulties she faced in her life. I felt that we are having a very special and passionate set of people as our lecturers not only in academic works but in life in general. In her lecture Dr.Shiromi highlighted a famous quote of great scientist Albert Einstein to convince us that sometimes we have to follow our intuition that comes from a deepest place in our heart since the rationality does not guide us in the right direction in life always. I return from this note leaving that great words here.

    “The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift.”
                           ― Albert Einstein