Reflections

One and a half year! It’s been around one year and 6 months since I reached Singapore. It has been a period filled with twists and turns – all of them, amazing. Now when I look back, I am proud to say that it has been one of the most rewarding periods in my life. Most importantly, the reason for what I came here for, I have completed with a (self) rating of exceeding expectations – Yeah! I graduated, with flying colors.
I came to Singapore for doing my masters. I was a bit afraid and didn’t have any idea about what to expect. My friends had warned that life will be very difficult without a job and friends. I truly hoped that I am prepared to start out from scratch, to get out from the comfort zone I was in, 1.5 years back. I vividly remember sitting at the stairs of my apartment (22nd floor) the night I reached here, alone, sipping a beer and thinking how I would feel or where I would be, two years down the line. And now, here I am, 1.5 years down the line, finishing my masters, with a group of amazing friends - just the way I always hoped for, with a job I always dreamed for and looking forward an exciting future.
When I made the choice to come here and purse higher studies, I could only hope that it would be a good decision. But now I can ‘state’ that it turned out to be one of the best decisions I have ever made. During the last 1.5 years, I have met some of my best friends ever, who are part of my life more than even I am part of my life, learned a whole lot of things (of course that was the main goal), more than that, the course sparked my interest in many fields I never thought I would find interesting (e.g. probability theory), found a job which is extremely satisfying, which allows me to do the things I love to do, met lots of people who opened up the whole new door of exciting opportunities that I can pursue. I learned to adapt to different environments, managed to balance work, study and personal life, learned to work under a hectic schedule, more than that, I learned how to keep my spirits up even when I had to work 24/7. I traveled a lot, experienced different things, met different people and discovered the world under the water & over the mountains and many others. The tenure at NUS exposed me to the amazing possibilities the world has to offer, or more accurately, the power of knowledge.

I can say from my heart that I have thoroughly enjoyed my learning experience in NUS, and I truly wanted to gain knowledge which is very different from my school days when I studied to somehow push through the exams. I know I have only managed to get a glimpse of the amount of knowledge out there, and that excites me. When I completed my undergraduate studies, I didn’t have a very good idea as on what is it that I want and I moved along the crowd. Now I know what is it that I want, or more like, what is it that gives me the feeling of “Wow! This is awesome; I want to do more of this”.
Above all, I would like to thank NUS and each & everyone who were (and still are) part of my journey - my parents, my sister & brother-in-law (who gave me the inspiration at times when I was down), my friends, my teachers, my colleagues, and to that occasional ‘stranger’ who gave me hope when I didn’t know what’s next, whom some people call, God.

EE5902 Multiprocessor Systems Qn. Paper

Subject: EE5902 Multiprocessor Systems
Department: ECE Dept, NUS
Semester I, AY 2009-10 Question Paper

Here I go again. My second exam for this semester also didn’t have previous year question papers published. Remembering the questions this time was a bit tough as it contained 20 one word type questions. I have somehow managed to remember bits and pieces of up to 16 questions. The rest, I hope my friends will help me. If you have attended this exam and have any comments about this post or if you know any missing questions, please post a comment. Please don’t mail them to me. I don’t need them. I am doing this in the hope that I may help some students in the upcoming batches. If you find this helpful, please leave a comment so that I know I have helped someone. Thanks to my 2 friends who helped me in remembering these questions.
Q1. [These questions are not in the order in which they are asked. I am putting the questions I remember in the order I jot down them right after the exam]
1. State only the correct statements
a. [Don’t Remember]
b. Data parallelism is not scalable [Something similar]
c. [Don’t Remember]
d. Control Parallelism is not limited by pipeline length
The correct statements are __________
2. [Summation]j,k [Summation]j,k(aik + bik) Computations like these are best suited in __________
3. Write a typical RT for a CV 1011 in the space provided (page 278)
4. __________ level parallelism is prohibiting the increment of factor k for a k-issue superscalar architecture
5. Baseline network has only one path from input to output (T/F)
6. For a superscalar processor of degree m and n instructions, as n tends to infinity, the speed up factor becomes __________ (notes chap 6, page 55)
7. Pentium is RISC in the higher level and computes CISC operations in the inner core level (T/F) (Notes Chap 3, slide 30)
8. If hit ratio of level Mi of memory is pi, the expression for access frequency for Mi __________ (Notes Chap 3, slide 69)
9. If the number of processing elements are between 1024 and 16384, it is typically considered to be a __________ (page 32)
10. If the time complexity of a problem is of O(2^n . n^2), it is clearly of polynomial complexity (T/F) (page 34)
11. What is the time complexity of the expression () [Forgot the exact expression]
12. MAL is greater than or equal to maximum number of check parks in the RT and less than or equal to the average latency of any greedy cycle. Also the average latency of any greedy cycle will be one greater than the number of ones in the initial collision vector. So, MAL is greater than the number of ones in the ICV. Point out what is wrong with this statement in the space provided below.
13. Non-linear pipelines and the reservation tables have a many to many mapping (T/F)
14. Loop level parallelism is considered to be __________ grain with less than 2000 instructions (Page 61 and it was given 200 instructions, not 500)
15. Power is proportional to the square of the frequency in embedded processors. (T/F) [Not sure about this statement, but it was relation between power and frequency which is given in slide 40 in the first lecture]
16. [One problem with coming up with an expression with some T1, T2, T3 and T3 and E1, E2, E3 and E4 for something. Don’t remember, I didn’t get time to look at this as this was the last question in the set]

Q2. We have a system with cache and memory. The cache capacity is 8 blocks and each block is one word. We have a 4 x 10 array, X(i, j) which is stored in main memory from address 7A00 to 7A27 in a column major fashion. (7A00 contains X(0, 0), 7A01 contains X(1, 0) etc). MM is also word addressable. The following program is executed

TOT = 0
For j = 0 to 9, do
TOT = TOT + x(0, j)
End do
AVE = TOT / 10;
For i = 9 to 0, do
X(0, i) = X(0, i)/AVE; /* Normalizing all the elements in the first row */
End do

Run the LRU algorithm on the above code for both the following scenarios
(i). Direct Mapping
(ii). Associative Mapping
Draw the mapping diagram also.
Hint: The memory is in hex [and some more, which I don’t remember]

Q3. A computer architect wants to connect 8 processor nodes to 8 memory modules using an MIN. He/she decides to use a baseline network, but wanted to have more connections from input to output and decided to have 5 stages. The first 3 stages – stage 1 to stage 3 – is done as normal self-routing network. Then from stage 5 through stage 3 is also self-routing network. For e.g., if we partition the whole network into two parts around stage 3, we will get exact mirror image. For this network, answer the following questions,
a. Draw the above stated network
b. How many paths are there for a given input-output pair
c. Device a strategy to route a given input node to an output node
d. A processor connected to the first switch in the first stage, P(0) is connected with memory module in the last switch in the last stage – M(7). Now the processor P(3) wants to connect to M(3). Show how the connections are reconfigured for the above design (qn. Q3 - c)

Q4. (Same question as problem 6.13 in text) For the same 4 pipelined stage in Qn 6.13,
a. Specify the reservation table
b. Find the collision vector
c. Draw the state diagram and mark the transitions

Q5. Formulate the differential equations for the reliability model for memory with state diagrams and with full equations (Same question as the reliability model for memory in notes)

[---- Questions Paper Ends Here ----]

Some doubts I had during my preparation for this exam. There are more which I never wrote down and now I don’t remember them. I had all these doubts by the end of my preparation which was just before the exam, so I didn’t get time to clarify them.

Qn. 19 in self test. The answer given is False. But in the text page 55 says “Bernstien’s conditions simply imply that two processes can execute in parallel if they are flow independent, anti independent and output independent”. Does it directly contradict the answer or is it ‘cos it doesn’t say anti-independence?
Qn. 28 in self test. The answer given is CRCW, but in text page 37, 38, it is clear that the ‘uncommon’ type is ERCW.
Qn. 43 in self test. “All processors need not be executing an instruction concurrently in a MIMD machine”. The answer for this one says False as per the self test answers, but the qn no. 10 in the qn bank “In a MIMD computer, all processors must execute the same instruction at the same time simultaneously” which is given as False too, directly contradicts this.

Page 346 in text. The input to the switch from both p1 and p2 shows e1 as the increment factor. It should be e1 and e2 right?
Can we consider pipelines as a MISD stage or a systolic array. Cos they are multiple fn units acting on a single data stream with specific function. In linear pipelines, the stages cannot be programmed. But in non-linear, different stages can be programmed also right?
In the Pentium, why do we need 2 bits for the history in the BTB? We need only one bit right?
Qn. 29 in self test, given a CV, how can we uniquely say the number of pipeline stages in the RT? Even is no stage is left unutilized in any cycle, the m of the CV will be less than n-1 right?

Some points I wish to note here, (just like my previous post)
1. I am not sure about the answers of the multiple choice questions and that is why I have given pointers to the page where they are mentioned.
2. There is no guarantee for any of these questions to be exactly the same as seen in the question paper. I simply wrote down what I remember after the exams.
3. I am publishing this the next day of my exams and so I don’t know the results, yet.
4. Please don’t send me mails asking for answers, please post comments in the comments section so that someone else may answer.

EE6902 Computer Communication Networks Qn. Paper

Subject: EE6902 Computer Communication Networks

Department: ECE Dept, NUS
Semester I, AY 2009-10 Question Paper

I wanted to do this from last semester onwards. There are some modules for which the previous question papers are not released by the department. I wanted to write down the questions and publish them. Maybe it will help someone in the coming semesters. Since I had back to back exams last semester, I was not able to do it. This semester, I have taken the module called computer communication networks which comprises mainly the fundamentals and concepts. The previous year question papers were not released and I and my friends wondered how to prepare for the exams or how the pattern of the questions may be. That’s when I decided this year I am going to write down and publish the questions as I remember them. I and my friend made small notes of the questions after the exam itself and now I made it to a better form.

If you are reading this for your exams, all the best and perform well. If you have attended this exam and know the missing questions or if there is anything to add to this blog, please do so by leaving a comment. If you find this ‘venture’ helpful, do leave a comment. After all, it feels good to know that I have helped someone. Special thanks to my friend Dana, who helped me a lot for my exams, without whom I would not have made this blog possible or even study well for the exam.





Some Notes:
1. There is no guarantee for any of these questions to be exactly the same as seen in the question paper. I simply wrote down what I remember after the exams.
2. Even though I answered most of the questions, I am not sure about the answers and also I am too lazy to write down the answers. As our professor says, give it a try.
3. I am publishing this the next day of my exams and so I don’t know the results, yet.
4. In the end of the questions, the symbol © doesn’t mean copyright. All copyrights are with the professor or the university (or with whomever it is). It just means ‘courtesy’. ;)

Newly Added
I am posting the answer for the question 2 here. This answer has been sent by my friend Ganesh. Thank you very much Ganesh :)

Designing a logo

I do bits and pieces of painting/drawing once in a while and I love almost everything that had anything to do with computer graphics. Electronic games are my weakness, but that’s mainly from a user point of view. Other interests are graphics programming, designing etc. Creativity has its own advantages. You can create, destroy or modify almost anything you want. More than that, I like playing God. So I jumped right in to the opportunity to design a new logo for our organization and my logo is selected as the new official logo.
Our organization - ARL - was on the process of revamping its website and the employees were given the choice of coming up with a new logo. We were free to come up with anything. No bounds were there. But it had to be agreeable to others in the lab. The main factors I had to keep in mind when designing a logo was that it should be easily printed on paper (in color, gray scale and black & white) as well as clothes (embroidery), stationery items like mugs, pens, plastic etc. Also the colors should stand the test of time and space (stretching, different media etc).
In the beginning, I was not sure whether I could do it. Finding the starting point was my main challenge. I had to formulate and idea and then start off from there. I kept thinking about it for some time and decided that I will start from where my predecessor stopped - the old logo. My plan was to rebuild the old logo first, may be with minor modifications in phase 1 and then add any new ideas as it comes along my way.

Old Logo

I looked at the old logo and asked myself, what are the key elements in there and what can I do to make them look better. After some thought and discussion with my professor, I decided to concentrate mainly on the following.
1. Make a new earth with glossy surface and a good reflection (inspiration: windows vista aero interface)
2. Make the bubbles, bubblier.
3. Decide whether to retain the waves or not. If retaining, try a different look. (The shell & waves are adaptation from the TMSI (Tropical Marine Science Institute) logo, to which ARL is affiliated to.)
4. New fonts for ‘ARL’.
I started with the earth part. The only tool I have used for the whole process is Adobe Photoshop. (Both ver. 7 and CS4). I searched the net for tutorials for a glossy globe and found this one.
http://www.denisdesigns.com/blog/2009/06/create-a-glowing-globe-icon-in-photoshop/
And that’s from where I started. The result of my first experiment looked like this.
Ok, now that I have a place to start from, I started playing with other factors like the bubbles, fonts, waves etc. Some of the tutorials I have used are given in the reference section. I downloaded custom brushes, fonts etc. My reconstructed logo, with new bubbles and font, but without the waves looked like this.
Ok, phase 1 is over. Now for the next phase, I wanted ideas, something that everyone will notice from the previous logo, at the same time, retaining the key elements of the old logo. That’s when I noticed the color combo of NUS website. Orange, blue and white. That’s from where I got the idea of using different colors. Ok, orange and blue, one of my favorite combos and at the same time, a theme which goes along with NUS website theme also. I had to start the logo all over again. The result looked much better than the green one (from my point of view).
I also had to create the ripples that originate Singapore. For that I found many methods/tutorials, but none was getting close to what I wanted. Then my professor sent me a link to try and voila! It worked. Also it was he who suggested keeping a simple font.
The result of my earlier experiments looked like this.
Another of my experiment with waves and without ripples resulted the following.
I ignored the idea of waves in the beginning itself as I was not able to do a nice work and it’s a bit difficult job and I was too lazy for that.
The above logos were used to collect feedback. Some of the main feedbacks received were, the ‘ARL’ text is not proportionate to the size of the globe, the gradient color scheme is difficult to do embroidery on t-shirts, the ripples are too small, since the ripples are there in the land, it given an impression of tsunami (We wanted the ripples to represent acoustic waves - showing the relation to our research domain) etc.
I redesigned again and came up with the final logo with bigger ripples explicit to the blue region (water) and a bigger single color ‘ARL’.

Final Logo

And that’s how this logo was born. Different versions of logo were made with different sizes, background (alpha channel), color/gray scale etc.
I never thought I will end up with this logo when I started. But when looking back, I feel great about this project. Special thanks for my professor who helped me from the starting point till I finished this project, with valuable advices and suggestions.
Along with the logo, I have also designed a simple map to reach our facility which you can find in the ‘contact’ page in our website. It was real fun making it.

References and tutorials which helped me in designing the logo
Glossy Globe
Bubbles
Text Effects
Ripples

Additional references and tips
Layer Masks
Custom Brushes
ARL
http://arl.nus.edu.sg/twiki/bin/view/ARL/Contact
http://arl.nus.edu.sg/twiki/bin/view/ARL/People
I am not an expert in photoshop, but drop in a comment if you think I can help you with photoshop.

Back to College Days: Trip to Melaka, Malaysia

I was going nuts trying to crack my wireless protocols assignment when that mail popped up in my maibox. “Trip to Melaka, Organized by NUS”, anyone interested? I believe in a principle which goes like, “Never say No to friends”. That’s how it all began.
Day: February 28, 2009, Saturday
Time: 0630

No no, its not the time when I woke up to study, but it was the time we gathered in front of the sports hall (our gathering point) to start our trip. I had no idea what to expect or what exactly is this trip about and what is there is Melaka. For me, it’s all about spending time with my friends and taking a break from my hectic schedule. So I didn’t have any expectation about my first international trip except that I knew there will be one more county’s stamp in my passport. But it turned out to be one of the most memorable days in my life and I went through a lot of feelings I thought was lost forever - the feelings and colors of college days - it felt like being back in my undergrad days.

Just like a dream!

A beautiful Chinese Letter carved in a rock in a temple. I have no idea what this means!

Old drawings in the wall of a temple

Our lunch and dinner was fabulous.

There are 2 things I like for a meal.
1. A delicious meal, as usual
2. A good company to start digging in to the task
And this was one of those rare occasions when I had both. For both lunch and dinner, there were around 7-9 dishes, with chicken, crab, prawns, fish, shark, vegetables (I didn’t concentrate in this area much), and dessert. Also, I think they were authentic Malay dishes, but since all of us were Indians, we had not much choice to get clear idea about the names of the dishes. Even if there were some means to get to know the names of the dishes, I seriously doubt we would have done that, ‘cos we were all very busy ‘fighting’ across the table that there was no time to talk.

A busy Melakan Street.

Since the city is kind of an old city, the streets are narrow. The buildings were painted really colorfully and you don’t get the feeling of a city.

In front of the Church of Christ

Who we are? (Click on the photo to read)

From Right
My House Owner : Aniket (My Housemate and a very dear friend)
My Financer : Ashwin (Friends for past 9 years)
Would be Dr. : Karthik (A new guy I met on the trip day, doing PhD in NUS)
Possible Roommate : Sampath (A possible future roommate)
Shashi Sir : Robin (A great friend who is my current roommate)
From Singapore : Girish (He is from Singapore itself)
Classified : Classified (;))
The Trouble Maker : Srijith (Karakku company)
Me : Me (You put your definition in the comment section)

A busy day in the Museum

Stairs to the courtyard or heaven?

F.R.I.E.N.D.S

Melakan Street: A view from the Top

An Ancient church in Melaka

This church - I think the name is St. Francis Chruch - is located on top of a small hill from where you get a really gorgeous view. It really was fun and soothing being there, enjoying the wind, and the songs of the native singers and there were several artists doing live drawing/paintings.

The Native Singers

A View from the Church

Tea Time: A Coffee shop in Melaka

Yeah, The Trouble Makers

No intro needed I guess. We went around looking for a coffee shop and had some fun and got lost from the group. We had to roam around for a while to find the group. Since it was another country, our mobiles didn’t work, we went back to the place where we started and the group was gone. Our choices were to go back to Singapore on our own - The Red Bus - or to go to the police station and ask for help. Before choosing from the above options, we asked some of the pedestrians for their mobile and called one of our friends and somehow got back to bus. And we heard some ‘sweet’ words from the ‘nice’ people who were waiting for us. The poor tour guide went around looking for us and came back exhausted to report he couldn’t find us, and we were there. Since he was a very good person, he didn’t tell us anything.

The End: The GSS group from NUS

I would like to thank all of my friends and whoever else who made that trip possible, because of whom I had one of the most memorable days in my life.
More Photos @ http://picasaweb.google.com/gssmalacca/TripToMelakaMalaysiaFromGSSNUSByManuIgnatius?#

ps: There are a lot more things I would love to write about this trip, but I am too sleepy now. Also, this was supposed to be a cultural trip.