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A guessing game…

I was playing this guessing game with a bunch of friends couple of days back, where each of us had a note pasted on our foreheads with a name of a famous person written on it. The goal was to guess the name, asking only polar questions. I was stuck trying to think of sports which doesn’t involve a ball (turns out I had Usain Bolt) and couldn’t help contemplating on the optimality of the questions asked. I found it kinda interesting, and hope you will too.

Here’s a simplified model of the game.
There are 2 players. S is a set having N (finite) elements, known to both players. Each player picks one element from S at random.

Goal:

  • Each player has to guess the element the other player has picked.

Rules:

  • A player, in his turn can ask yes-no questions.
  • If the answer is ‘no’, the turn passes to the other player.
  • If the answer is ‘yes’ the player retains his turn, up to M number of consecutive questions.(i.e. after M questions, the other player gets the turn)

Q1. What is the optimal strategy (best questions to ask) for a player?
Optimal = the expected number of turns taken to correctly guess is minimized

Q2. What is the maximum number of turns a player would need to arrive at the correct element?

p.s.
Hint:
From an information theory perspective, the idea is to maximize the information from each turn, with different probabilities of yes/no.

p.p.s.
Another important question on a different note.
Q3.What is the probability that someone thinking of optimal strategies in party-games would be invited again to one? (given that the crowd is just as geeky) :p

Posted in Puzzles. Tagged with .

By Madushanka
June 11, 2010

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Got a bike.. Yay!

The bike

I bought a bike, which is a lot more affordable mode of transport in the summer term, as I have to buy a bus pass otherwise. Not only that, riding a bike is much more fun than coming in the bus. Considering the walking distance to the bus stops, and the waiting times, this is much quicker as well.

I thought of buying a cheap used one, since everyone was saying that there is a high risk of bikes being stolen. There, indeed, are quite a few such incidents. people either steal the whole bike, or parts like wheels, seats or lights. It is somewhat irrational, coz bikes are not that expensive, and it’s hard to imagine people wanting to steal an old bike. Still, I decided to buy a used bike, as used bikes are less attractive to the thieves.

It’s not the best bike you could have. The chain is a bit lose, which means I cant put much force on the pedal. It is kind of a annoying, but since the land is very flat here, it is OK for day-to-day activities.

Although it is a crappy bike, I am much excited to have it. Having a bike means that i get to ride along the paths in the river valley during the summer. I am looking forward to do that. Although not much, the bike does offer more travelling area.. which means more to experience.. more possibilities. EXCITING!!! :-)

————————————–
Things to check when buying a used bike, in order of importance IMHO.

  1. Brakes – whether the brakes work / how good in terms of breaking distance.
  2. Gear system + chain – does the gear mechanism work, is the chain ok(not lose) in all modes.
  3. Wheels – how worn out
  4. Frame – strength, signs of corrosion
  5. Seat.  – how comfy

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By Madushanka
May 22, 2010

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Book::Fundamentals of Wireless Communication

I am going through Dr David Tse’s book(Fundamentals of Wireless Communication-David Tse and Pramod Viswanath) on wireless communications these days. I found it a very interesting read.

A draft version of the book can be found here http://www.eecs.berkeley.edu/~dtse/book.html.

And there is a video of a short course by David Tse, which is based on the book, can be found here. The videos are quite useful to grasp the general idea of the main points, and watching it before reading the book is likely to make understanding the content easier.

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By Madushanka
May 21, 2010

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A year later..

My last post here was more than a year ago!

I was surprised to notice this,  because I was under the impression that I enjoy writing.  I am pretty sure I have it listed under my hobbies. Yet, I did not actually make any new posts for over an year.

Well, you can’t do everything you want. There are many things limiting your daily life. I think about the time you graduate from high school, the limiting factor in your life becomes ‘time’. I saw in a comic similar to this, that when you are a kid it’s money, and when you get old it’s energy, that limits our experiences. So I think right now, my hobbies are limited by the  amount of time I have.

Understanding this becomes an important point in prioritizing things in our lives. If you realize in your life the bottleneck is time, that should be the governing element in your choice of activities. Managing your time becomes much more important than balancing your account. Making sure time is spent for the right things, at this stage, is key to living your life.

So, right now, the question is, do I have time for this? Well, over the last year I must have wasted quite enough time to write a book! But I must have had things that I’d rather do, than writing.That is the only explanation.  So, may be I must take it off my hobby list.

Anyway, writing for me, was somewhat an acquired taste. I need to like writing, because it is becoming increasingly important in my work as a grad student. Hence, I think I should put more time for this. Hopefully, the next post will come before another year.

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By Madushanka
April 28, 2010

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A traveller at the sunset…

You look so alluring, with a golden hue..
a feast to the eyes, painting a heavenly view..
I hold my gaze, in these moments too few..
you appear grander than ever, at this hour of adieu..

For the warmth of your hugs, of rays so golden..
for the shine of your smile, that brightened my way..
I’m grateful, indebted; it’s true, I’m beholden..
I whisper to myself, amidst a dusk so grey..

I will move on, my lips let out a sigh..
This is not my stop, no, not what I had in mind..
You wouldn’t rise from the west, oh! is this good bye..
At a point of no return, a way forward, I must find

I summon my energy, my luggage weighing me down..
take it off my back, should I, but it’s all that is mine..
the memories so precious, of your smile and the frown..
all I held dear obscured, with the fading sunshine..

as shadows creep over, I’d need a blaze, just as bright..
a star down the road, a ray of hope at the onset..
to brighten up my world, and to leave me in a plight..
with a darkness veiling the shadows in a sunset..


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By Madushanka
January 10, 2009

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Rab Ne Bana Di Jodi

I got to watch a hindi movie after a looong while, and I believe this is the first one I watched in theatre. Well, I’m not a big fan of bollywood movies, but I did not think this movie was totally useless. ;-)

In a nutshell, the plot is about 2 ppl, getting into a relationship without love, and the guy faking a different personality to win the love of his wife. Well, it is not this simple, but I wouldn’t wanna ruin it for those who dint watch it yet.

As any hindi movie, this puts too much drama in every thing. The way the 2 ppl gets in to the relationship, the sudden ability of the guy to emulate a very different personality and few other aspects take this a bit further from being very realistic. Forexample, the extreme lack of intimacy in the original relationship, the inability of the wife to see through the very little disguise, the fight with the sumo player, the guy knowing exactly how to make the girl happy in his disguise and not even making the faintest sign in his original self are few of the points that make the plot a bit unrealistic.

Having said that, I still found the underlying messages somewhat interesting.
1. Dancing classes are great places to pick up women
2. Never let your wife go to a dance class alone. :D :D
yeh… i was just kidding..
1. One interesting idea is the tendency to look outside your relationships to get what you are missing, and overlooking some important things in your original relationship. This is not a very rare situation in any real relationship, and the conflict of choices between the exciting new relationship and the boring existing one seem to be well communicated, although I feel this plot is not the best way to present that theme.

2. The other theme I find interesting is the struggle of the guy including changing his personality to win the love of his wife. The conflict inside him between these personalities is also interesting, since he knows, although it wins the love of his wife, the new personality is not the real him. I believe, he not wanting to change himself to suit the relationship, and expecting his wife to appreciate his silent acts of love is very understandable. Because, changing one’s self to suit a relationship is not gonna be very effective in the long run, in my opinion.

The acting of Sharukh Khan, I thought, was really good, showing lot of emotion. And there were many funny moments, that do make u laugh. ;-)

But like many hindi movies, this wasn’t a very intelligent movie. The plot wasn’t the most realistic, and the movie was very one dimensional. In the main guy’s role, the only aspect shown is his relationship with his wife. His professional relationships, other personal relationships, or any other aspect wasn’t discussed much. This movie reminded me a bit of “Shall we dance”, and the conflicts the guy in that faced, with his family and the new interest. Shall we dance, in comparisan presented a lot wider perspective of the character. I don’t get why most of the hindi movies present relationships as the soul/main purpose of life, which is not a realtity for most people now.

I wouldn’t know exactly how this ranks against other hindi movies, but I think this is a good movie in bollywood standards. If you are looking for some light humour and romance, and not mind the unrealistic plot, I believe you would enjoy this one. Well at least I did.. :-)

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By Madushanka
December 25, 2008

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I’m an INTP

Myers-Briggs Type Indicator is, I believe, the most widely used personality type categorization currently used. It identifies 16 types of personalities, according to factors like introversion-extroversion approach for decision making, etc.. It basically checks whether you are more of an introvert or extrovert, intuitive or sensing, perceiving or judging and feeling or thinking. I first took this test a few years back, and quite recently again. I found the results very interesting.. Here’s what I got..

INTP

Rodin’s Thinker is introverted. Here these thinkers ponder the apparent chaos of the world in order to extract from it the universal truths and principles that can be counted on. These principles, once extracted, will provide the logical structure on which to build strategies.

They have a finely nuanced ability to analyse situations, find root causes and foresee consequences. They distrust action taken too quickly without the necessary investigation. They are usually levelheaded, objective, impersonal yet intensely involved in problem solving. They are fiercely independent, seeking input and comments from a chosen few. When reporting to others, they need to establish credibility first: their own and that of the person they are reporting to. If the gap in knowledge and expertise is too great and their own proficiency dismissed, belittled or ignored, they will lose interest and motivation.

They are less interested in running the world as they are in understanding it. They are curious and capable of explaining complex political, economic or technological problems, taking great pleasure in explaining all the factors and intricacies. They are rigorous with their thoughts and analysis, choosing the exact words that convey precisely what is meant. They may spend a lot of time defining words, concepts and systems in order to define a problematic solution.

They are armchair detectives, scientists and philosophers, spending most of their time in quiet reflection to ponder truth, and solve mysteries. They may tend to neglect social requirements and responsibilities, finding many relationships to be too superficial to be of much interest.”

Well, the description is not very far from the truth, i guess.

The important thing about these kinda tests is that they help our self discovery a lot. It’s not only about finding out who ywe are.. but also finding out where we’re good at.. and where we can improve. We can see the basic assumption or values that we build up on, and most importantly would help understanding the other personality types. I have a good friend of mine who is a complete opposite to me in the personality type (an ESFJ), but knowing that we have very different personality types helped a lot in improving our friendship..

You also can check your personality type by answering the questions here.
To find out about your personality type, thisis a good source.

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By Madushanka
December 24, 2008

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My sister’s keeper

New York Times bestselling author Jodi Picoult is widely acclaimed for her keen insights into the hearts and minds of real people. Now she tells the emotionally riveting story of a family torn apart by conflicting needs and a passionate love that triumphs over human weakness.

Anna is not sick, but she might as well be. By age thirteen, she has undergone countless surgeries, transfusions, and shots so that her older sister, Kate, can somehow fight the leukemia that has plagued her since childhood. The product of preimplantation genetic diagnosis, Anna was conceived as a bone marrow match for Kate — a life and a role that she has never challenged…until now. Like most teenagers, Anna is beginning to question who she truly is. But unlike most teenagers, she has always been defined in terms of her sister — and so Anna makes a decision that for most would be unthinkable, a decision that will tear her family apart and have perhaps fatal consequences for the sister she loves.

My Sister’s Keeper examines what it means to be a good parent, a good sister, a good person. Is it morally correct to do whatever it takes to save a child’s life, even if that means infringing upon the rights of another? Is it worth trying to discover who you really are, if that quest makes you like yourself less? Should you follow your own heart, or let others lead you?”

My sister’s keeper is one of the most interesting books I’ve read.. eh, not literally though.. you see, I couldn’t find the book.. so i settled for the next best option.. the aduio book.. I found in demonoid.com..

The story goes is told in first person.. I normally like first person narratives.. here the the main characters takes turns in narrating the chapters.. giving full accounts of the story pressenting different perspectives..

The story is a good read on human relationships.. simply, how much hard work they requires.. the committment.. It was also interesting to see the subjectivity of viewpoints.. you know, how often we are having a misconception on something.. sometimes because we don’t know the story.. or lack of communication.. or someitimes, simply because we don’t want (or can’t afford) to see..

I found the story remarkable.. with the great twist at the end.. (only after a friend of mine told that I noticed, the prologue even isn’t what it first appears to be..)

I can’t say i liked how things end.. and it goes on to emphasise few other messages of the story..
the first would be…”people think that they know what they are getting.. but most of the times, they don’t..”

and the other “life isn’t fair”…

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By Madushanka
July 10, 2008

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Final year at uni…

I started my final year at uni..the first semester of the 4th year in my undergraduate degree.. 
It has being 6-7 months since the end of last semester, since we were out in the industry as full time interns meanwhile.. 

It is not quite fun coming back to the lecture-assignment-exam life again..
The only consolation is that I get to spend more time with my friends.. 
Still, I can’t believe that there is only one year left in my uni life as an undergraduate.. the time flies indeed.. the 3 years passed doesn’t even feel like few months..

The life after graduating is going to be lot more fun, I believe.. and I am excited to step out of this uni.. excited about the new opportunities and experiences it’s gonna lead me to.. 
But I still am gonna miss this.. the boring lectures.. hanging out with friends. etc etc..

I guess.. no matter how interesting the prospects are.. it is still kinda worrying to let go of the past.. change is scary.. 

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By Madushanka
June 24, 2008

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CIMA Exams

phew.. the exams are finally over.. I was studying for my CIMA exams for the past few weeks.. during my uni hols.. It is not quite fun to get stuck in an exam while most of your friends are partying and enjoying the hols..

Anywho.. the exams were tough… and I ran outta time in 2 outta 3 papers.. and I would be quite surprised if the marker find my handwriting legible..

The content in CIMA is quite interesting.. The stategy making process.. the organizational behaviour analysis.. investment decission analysis.. all these are beyond my scope as an engineering undergraduate and I simply love the additional ways of thinking and analysing that it offers me..

Still.. exams suck no matter how interesting the course contents are..:-)
The results won’t be out for few months..
and I just have to wait and see how things went..

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By Madushanka
May 22, 2008

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