Saturday, January 05, 2013
Disappointed
I am disappointed that the PM threatened yawningbread with libel. I've been going around telling my friends in the US: "Actually, times have changed, the government is opening up to criticisms and as long as you don't say these few things you're gonna be fine." Looks like I was wrong. I have nothing to say to the US critics of Yale-NUS.
Sunday, December 30, 2012
Saturday, December 29, 2012
Sexism in Tech
I understand that whatever I'm writing here can be used against me. But I still believe that people should be judged for who they are and not who they seem to be, and I hold myself to this standard. I just hope that whoever happens to chance upon this inactive blog in the future understands that I wrote this as a 23 year old and I may have changed by the time you're reading this. If I haven't, then judge me as appropriate.
I read this article recently: http://news.ycombinator.com/item?id=4980350
Before reading this article, I hadn't realized how big of a problem sexism in tech is. Man, I really feel for all the crap the writer had to go through. I can't empathize, but I know it must have felt worse than anything I've been through. But at that same time, I know that I have perpetuated this myself - I remember that at the first day working at BloomReach (a tech company), when Helen introduced herself to me, the first thing that I noticed was that she's cute. And the first question that popped to my mind was, "Are you an engineer?", because I've heard that women are underrepresented in engineering roles in tech and I wanted to check my hypothesis. She smiled and defused the question really well, but it was only after I read some other article that I realized the undertone in that question.
And so I realize I'm part of the problem. I am biased. When I find out that a woman I haven't met before is in tech, it genuinely comes to me as a surprise (especially if she's attractive, but that's another stereotype). Unconsciously, my words reveal my beliefs, and they make them feel a little smaller.
Why is this a problem? After all, stereotypes can serve as mental shortcuts that allow us to arrive at better decisions with less information. It is not factually wrong to claim that since women are underrepresented in tech, if the only information I am given is that this person is a woman, then the conditional probability that she's not in tech is higher than otherwise. So if I were to go up to a random woman(not in the CS department building of course) and say, "you are probably not a CS major", I would be right most of the time. But that makes her feel bad and doesn't achieve anything. So I know not to say it.
Alright, so I shouldn't voice out my beliefs based on stereotypes that make people feel threatened. But if it's likely to be true, I am still justified in believing it, right? Why should I be blamed for attempting to arrive at a belief that's more likely to be correct than not?
I think the problem here lies with priming. I'm not surprised at all when a guy tells me he's in tech - why? The base rate of people in tech isn't really that high in the first place. The difference, I think, is the bunch of concepts that pop into my head (aka the schemata that get activated) when I see a person. Somehow(just guessing), the schema for "probably not a tech person" gets activated when I see a girl but not when I see a guy, even though the belief would be justified for both guys and girls.
I really can't think of a "thinking cure" or "reading cure" for my bias. But I know of one method that has worked for me in the past. I previously held the stereotype that girls aren't good at math. But Elaine blows me out of the water when it comes to math, and working with her on psets has shattered this stereotype for me. I suppose if I had done psets with Irene it would nuke the stereotype into oblivion(along with whatever ego I started with), but I'm not at the level where I'm even taking the classes she's taking.
That might work.
(Unrelated random trivia: Lisa Einstein is currently studying undergrad physics at Princeton.)
Thursday, December 20, 2012
Monday, December 10, 2012
Reconciliation
Yesterday, I saw a video from North Korea about American propaganda. Despite the disapproving tone and wide generalizations, I think they've got some things right. It's an hour and a half long, but I think it's worth watching. (Also note that the translator now has some doubts about whether this film is really targeted at DPRK citizens or are actually targeted at the global population.)
In summary, the video is about how the US uses the media to maintain a consumerist culture and keep its citizens ignorant and "enslaved", so that they don't spend time thinking about things that really matter. It discusses how advertisements, celebrities, the War on Terror, and empty catchphrases are used to achieve this, how the US consumerist culture is unsustainable, and why people in the US are not truly free.
I was intrigued by this video, so I asked people about their thoughts on it over brunch.
"Oh, propaganda about propaganda? Propagand-ception!"
"It's from North Korea? They're not doing so well themselves either."
"What's wrong with a consumerist culture? Is there something that matters more than economics? Anyway you should watch this movie about North Korea invading the US, it's like top ten in the box office."
And they continued talking about their favorite food, sports teams, and the flowers in the middle of the table. Sigh. I guess these things matter a lot to them.
-------------------------
So here are my thoughts.
A preface to talking about "consumption"
One easy trap to fall into when talking about consumerism is using the word consumption to describe anything we do in order to make it sound like it is a bad thing to do, then using a different set of vocabulary to talk about an alternative in order to make the alternative sound like a "solution" to the "problem". The video commits this mistake a lot. Whenever the video talks about consumption, it shows footages of morbidly obese people eating junk food to viscerally cement the point that consumption = bad. But a farmer eating rice with beanstalks after a hard day of work is also consumption. So is taking the train. Many things we do are acts of consumption, and you have to do some of it to remain as a productive member of society. You have to eat something. You have to dress appropriately for your job interview. You have to go school because it helps you make better decisions, and the decisions you make affect others. All these are acts of consumption in some form, but few will argue that they are bad things to do. So consumption ≠ bad. But consumption is a word loaded with bad connotations, so I'll avoid using this word.
Balancing out the video's tone
The video claims that a consumerist culture is the result of a positive feedback loop in a capitalist economy:
1) People want to buy things. People who make and sell goods want to buy things too, so they want to make more money.
2) To make more money, corporations need to sell more goods, so they advertise aggressively. The most effective advertisements have an effect of making people want to buy their things. Go back to 1).
But the implicit message is that in such a culture, when people buy and use/eat things,
1) They are only doing it to make themselves feel better. It implies a hollow and ultimately unfulfilling existence. This is essentially the problem of how one can possibly find meaning in life if one subscribes to utilitarianism. It's a philosophical problem and capitalism did not cause it.
2) They don't do anything else. Since corporations strongly affect what people want to buy, by controlling what people buy they effectively control how people live, and thus the people are "enslaved". Well, this is not true. When someone buys a camera, it's generally for taking photos and not "look I have a camera I am cool". The things you own facilitate what you already want to do. It would take a fantastic leap of reason to argue that an artist who buys a canvas is a slave to consumerism just because he/she bought something from a corporation. Using something that you have bought is also not just a passive act that merely fulfills a hollow desire. You can use a cell phone's text messaging function to meet up with friends. A husband can also use his car to drive his pregnant wife home(shout out!). People want to be nice to each other and will do it in any way they want. There is still a great deal of freedom in a world where almost everything you use has to be bought with money.
3) They mostly buy things they don't need. Technically you don't need a camera to survive. Technically you don't need books either. Or vaccines. But now that technology has granted us such powers, why not use it? Good reasons: You could have spent that money on better things. It's bad for the environment. Bad reason: You don't need it to survive.
So the big problem that the video makes that it assumes that life in a consumerist culture is inherently unfulfilling. It need not be. But one thing they did bring up is: people could, theoretically, live happier and healthier lives with less impact on the environment, so why aren't we doing it? I think this is a good point. But there is the problem of how such a life is going to look like. The next problem is how we get there and stay there. It's hard though, because many people are already used to a certain lifestyle and it would be a very disruptive change. (People have tried disruptive changes before, but it didn't work.)
Is there a point to it though? Even if we are not making cultural progress, there is definitely progress in infrastructure and science. If the Earth is all we have to care about, then if we can find the "meaning to life", not having scientific and technological progress that doesn't really matter either. But we'll all be fucked if an asteroid comes along.
The problem of sustainability is a big problem for capitalism though. Perhaps capitalism causes such a strain on the planet that it doesn't even make sense to worry about asteroids. I don't know. But the technology actually exists to solve our problems, it's just that incentives are currently not aligned correctly for everyone to act in the optimal way. When solar/fusion power becomes available on a large scale, we're going to be okay.
In summary, the video is about how the US uses the media to maintain a consumerist culture and keep its citizens ignorant and "enslaved", so that they don't spend time thinking about things that really matter. It discusses how advertisements, celebrities, the War on Terror, and empty catchphrases are used to achieve this, how the US consumerist culture is unsustainable, and why people in the US are not truly free.
I was intrigued by this video, so I asked people about their thoughts on it over brunch.
"Oh, propaganda about propaganda? Propagand-ception!"
"It's from North Korea? They're not doing so well themselves either."
"What's wrong with a consumerist culture? Is there something that matters more than economics? Anyway you should watch this movie about North Korea invading the US, it's like top ten in the box office."
And they continued talking about their favorite food, sports teams, and the flowers in the middle of the table. Sigh. I guess these things matter a lot to them.
-------------------------
So here are my thoughts.
A preface to talking about "consumption"
One easy trap to fall into when talking about consumerism is using the word consumption to describe anything we do in order to make it sound like it is a bad thing to do, then using a different set of vocabulary to talk about an alternative in order to make the alternative sound like a "solution" to the "problem". The video commits this mistake a lot. Whenever the video talks about consumption, it shows footages of morbidly obese people eating junk food to viscerally cement the point that consumption = bad. But a farmer eating rice with beanstalks after a hard day of work is also consumption. So is taking the train. Many things we do are acts of consumption, and you have to do some of it to remain as a productive member of society. You have to eat something. You have to dress appropriately for your job interview. You have to go school because it helps you make better decisions, and the decisions you make affect others. All these are acts of consumption in some form, but few will argue that they are bad things to do. So consumption ≠ bad. But consumption is a word loaded with bad connotations, so I'll avoid using this word.
Balancing out the video's tone
The video claims that a consumerist culture is the result of a positive feedback loop in a capitalist economy:
1) People want to buy things. People who make and sell goods want to buy things too, so they want to make more money.
2) To make more money, corporations need to sell more goods, so they advertise aggressively. The most effective advertisements have an effect of making people want to buy their things. Go back to 1).
But the implicit message is that in such a culture, when people buy and use/eat things,
1) They are only doing it to make themselves feel better. It implies a hollow and ultimately unfulfilling existence. This is essentially the problem of how one can possibly find meaning in life if one subscribes to utilitarianism. It's a philosophical problem and capitalism did not cause it.
2) They don't do anything else. Since corporations strongly affect what people want to buy, by controlling what people buy they effectively control how people live, and thus the people are "enslaved". Well, this is not true. When someone buys a camera, it's generally for taking photos and not "look I have a camera I am cool". The things you own facilitate what you already want to do. It would take a fantastic leap of reason to argue that an artist who buys a canvas is a slave to consumerism just because he/she bought something from a corporation. Using something that you have bought is also not just a passive act that merely fulfills a hollow desire. You can use a cell phone's text messaging function to meet up with friends. A husband can also use his car to drive his pregnant wife home(shout out!). People want to be nice to each other and will do it in any way they want. There is still a great deal of freedom in a world where almost everything you use has to be bought with money.
3) They mostly buy things they don't need. Technically you don't need a camera to survive. Technically you don't need books either. Or vaccines. But now that technology has granted us such powers, why not use it? Good reasons: You could have spent that money on better things. It's bad for the environment. Bad reason: You don't need it to survive.
So the big problem that the video makes that it assumes that life in a consumerist culture is inherently unfulfilling. It need not be. But one thing they did bring up is: people could, theoretically, live happier and healthier lives with less impact on the environment, so why aren't we doing it? I think this is a good point. But there is the problem of how such a life is going to look like. The next problem is how we get there and stay there. It's hard though, because many people are already used to a certain lifestyle and it would be a very disruptive change. (People have tried disruptive changes before, but it didn't work.)
Is there a point to it though? Even if we are not making cultural progress, there is definitely progress in infrastructure and science. If the Earth is all we have to care about, then if we can find the "meaning to life", not having scientific and technological progress that doesn't really matter either. But we'll all be fucked if an asteroid comes along.
The problem of sustainability is a big problem for capitalism though. Perhaps capitalism causes such a strain on the planet that it doesn't even make sense to worry about asteroids. I don't know. But the technology actually exists to solve our problems, it's just that incentives are currently not aligned correctly for everyone to act in the optimal way. When solar/fusion power becomes available on a large scale, we're going to be okay.
Sunday, December 09, 2012
I remember one year ago, I asked a Romanian, "So Romanian uses the English alphabet?"
The reply: "English uses the roman alphabet."
---------fast forward---------
"Ah I see, so you speak English in Singapore. But where does the accent come from?"
"I don't have an American accent because I'm not from America."
The reply: "English uses the roman alphabet."
---------fast forward---------
"Ah I see, so you speak English in Singapore. But where does the accent come from?"
"I don't have an American accent because I'm not from America."
Thursday, November 29, 2012
Can the flaws in the MCMC algorithm give some insight on stereotyping?
Stereotyping = guessing based on prior assumptions. Tends to be more accurate than guessing at random.
Why bad? People less likely to recognize individual differences and focus on group differences, which may be of a small magnitude. Humans are limited - focus on group differences => less attention to individual differences (Side note: less attention to individual differences = bad? Or only in individualistic cultures like US?)
Flaw of MCMC algorithm: the sampling process is biased, especially when features are highly correlated. Positive feedback loop, occasionally broken by chance. Slow convergence. Similar to stereotyping? Less accurate, and tends to "jump to conclusions".
Stereotyping = guessing based on prior assumptions. Tends to be more accurate than guessing at random.
Why bad? People less likely to recognize individual differences and focus on group differences, which may be of a small magnitude. Humans are limited - focus on group differences => less attention to individual differences (Side note: less attention to individual differences = bad? Or only in individualistic cultures like US?)
Flaw of MCMC algorithm: the sampling process is biased, especially when features are highly correlated. Positive feedback loop, occasionally broken by chance. Slow convergence. Similar to stereotyping? Less accurate, and tends to "jump to conclusions".
Wednesday, November 28, 2012
random thoughts
Random ideas:
Is it feasible to scan entire books without flipping any pages?
- Approach: Powerful beam of focused light that passes through the pages. Focal length can be changed to provide more data points. Page boundaries can be discerned by the difference in absorbance of paper, laminate and ink.
- Difficulties: Thick hard-cover books would be quite opaque. Difficult for sensor to discern print on pages that face each other. Noise due to paper grain.
- Easier workarounds: Mechanical page flipper. In fact, it probably already exists.
VCG mechanism (which is truthful in DRM under non-negative valuation, non-positive external contribution and quasi-linear utility domain) is not collusion proof. It's truthful because telling the truth is the Nash equilibrium. However, Nash equilibrium does not imply sub-game perfect. VCG is also not collusion-proof. But interestingly, it seems that Nash equilibrium, if we consider for simplicity that the action set is continuous and differentiable, only considers the first and second derivatives of the multi-dimensional mapping between utilities and utilities (for each outcome rule assuming a dominant strategy exists for all players and they play that). Wait, it's not a derivative of a function - it's a derivative of many functions. Darn. I'm wondering if there is an many-to-many mapping equivalent of a Hessian determinant. If there is, it would probably be completely useless, but still kinda cool. The real solution might not even give any insight since non-integral indices doesn't mean anything at all in this scenario.
My first-world problem: Watching a youtube video on developing countries when I have a slow internet connection, and feeling guilty and annoyed at the same time when it stops to buffer.
Also, reading the Communist Manifesto while listening to "Do you hear the people sing" is pretty awesome.
I remember vaguely that I would once have used words other than "a mapping from the set of combination of clothes to days" in a dinner conversation. Nowadays it feels like a completely normal and natural way of saying something that everyone can understand. Thanks Charter club. (I think the words would have been a choice of outfit, but I'm not sure if my mouth has ever uttered these words before either.)
Quora is amazing. But I still think the problem of people repeating arguments that have a set of good counter-arguments still hasn't been adequately solved. I want to learn more about what it takes to build a large information system, and it's looking rather intimidating. There is the computational component, the incentive component, and the business component. I mean, holy crap it's a hard problem. But I still think it's absolutely worth solving. Branch is doing nicely on part of allowing people to debate on issues that branch out, and stack exchange is doing well on the community edited answers front. In fact, stack overflow is fantastic on search - if the top thread on google isn't the question you're asking, one of the "related questions" probably is. It's amazing and worth emulating. Stack overflow is solving one of the problems on forums. But debates aren't handled very well, and the available solutions still disappoint me. What I would like to see is more scoring of responses to arguments. Quora allows embedded quotes. That is fantastic - I would like the whole internet to allow embedded quotes, so that attribution is easy.
Seriously though, can we have embedded quotes for the whole internet? What would it take? First problem - webpages change. Can't archive everything - too much space needed. A browser tool for a generating citation on the fly? That would be nice, but seems a bit intrusive. Yeh, attribution of a source in a user-friendly yet informative and structured way is hard. Reproducing the source wholesale could probably do it. Sounds like a job that "turn it in" has already figured out though, so the infrastructure definitely already exists.
"Ideas" are difficult to handle - it's so context dependent. A probabilistic approach is good at figuring out the topic, but is it good at figuring out the meaning?
I wonder what hardwired parameters our brains have. What is the "corpus" of a human being? It would be interesting if we can get hold of all the sensory inputs to a child from birth onwards. What does the baby know about the world when it's born, and how much of it was learnt from experiences in the womb? (Alas, hard to know)
Implementing an MCMC algorithm for Bayesian reasoning is pretty interesting. There was this case where all the nodes reinforced each other, and the algorithm took a really long time to converge - because the chance of the algorithm "changing its mind" about the central node's value. It makes me wonder if that is somehow related to religious beliefs - strongly reinforcing nodes. But that requires a certain model of reasoning.
Thoughts on a model of reasoning (I'm sure the cogn-psy peeps have figured out a large part of it, but I guess I can always ramble). People can hold on to inconsistent beliefs. People only reason some of the times, and believe what has been said most of the time.
Is it feasible to scan entire books without flipping any pages?
- Approach: Powerful beam of focused light that passes through the pages. Focal length can be changed to provide more data points. Page boundaries can be discerned by the difference in absorbance of paper, laminate and ink.
- Difficulties: Thick hard-cover books would be quite opaque. Difficult for sensor to discern print on pages that face each other. Noise due to paper grain.
- Easier workarounds: Mechanical page flipper. In fact, it probably already exists.
VCG mechanism (which is truthful in DRM under non-negative valuation, non-positive external contribution and quasi-linear utility domain) is not collusion proof. It's truthful because telling the truth is the Nash equilibrium. However, Nash equilibrium does not imply sub-game perfect. VCG is also not collusion-proof. But interestingly, it seems that Nash equilibrium, if we consider for simplicity that the action set is continuous and differentiable, only considers the first and second derivatives of the multi-dimensional mapping between utilities and utilities (for each outcome rule assuming a dominant strategy exists for all players and they play that). Wait, it's not a derivative of a function - it's a derivative of many functions. Darn. I'm wondering if there is an many-to-many mapping equivalent of a Hessian determinant. If there is, it would probably be completely useless, but still kinda cool. The real solution might not even give any insight since non-integral indices doesn't mean anything at all in this scenario.
My first-world problem: Watching a youtube video on developing countries when I have a slow internet connection, and feeling guilty and annoyed at the same time when it stops to buffer.
Also, reading the Communist Manifesto while listening to "Do you hear the people sing" is pretty awesome.
I remember vaguely that I would once have used words other than "a mapping from the set of combination of clothes to days" in a dinner conversation. Nowadays it feels like a completely normal and natural way of saying something that everyone can understand. Thanks Charter club. (I think the words would have been a choice of outfit, but I'm not sure if my mouth has ever uttered these words before either.)
Quora is amazing. But I still think the problem of people repeating arguments that have a set of good counter-arguments still hasn't been adequately solved. I want to learn more about what it takes to build a large information system, and it's looking rather intimidating. There is the computational component, the incentive component, and the business component. I mean, holy crap it's a hard problem. But I still think it's absolutely worth solving. Branch is doing nicely on part of allowing people to debate on issues that branch out, and stack exchange is doing well on the community edited answers front. In fact, stack overflow is fantastic on search - if the top thread on google isn't the question you're asking, one of the "related questions" probably is. It's amazing and worth emulating. Stack overflow is solving one of the problems on forums. But debates aren't handled very well, and the available solutions still disappoint me. What I would like to see is more scoring of responses to arguments. Quora allows embedded quotes. That is fantastic - I would like the whole internet to allow embedded quotes, so that attribution is easy.
Seriously though, can we have embedded quotes for the whole internet? What would it take? First problem - webpages change. Can't archive everything - too much space needed. A browser tool for a generating citation on the fly? That would be nice, but seems a bit intrusive. Yeh, attribution of a source in a user-friendly yet informative and structured way is hard. Reproducing the source wholesale could probably do it. Sounds like a job that "turn it in" has already figured out though, so the infrastructure definitely already exists.
"Ideas" are difficult to handle - it's so context dependent. A probabilistic approach is good at figuring out the topic, but is it good at figuring out the meaning?
I wonder what hardwired parameters our brains have. What is the "corpus" of a human being? It would be interesting if we can get hold of all the sensory inputs to a child from birth onwards. What does the baby know about the world when it's born, and how much of it was learnt from experiences in the womb? (Alas, hard to know)
Implementing an MCMC algorithm for Bayesian reasoning is pretty interesting. There was this case where all the nodes reinforced each other, and the algorithm took a really long time to converge - because the chance of the algorithm "changing its mind" about the central node's value. It makes me wonder if that is somehow related to religious beliefs - strongly reinforcing nodes. But that requires a certain model of reasoning.
Thoughts on a model of reasoning (I'm sure the cogn-psy peeps have figured out a large part of it, but I guess I can always ramble). People can hold on to inconsistent beliefs. People only reason some of the times, and believe what has been said most of the time.
Monday, November 19, 2012
Warm fuzzy
I'm really moved today.
I'm in Charter Club (one of the eating clubs in Princeton), and honestly, I haven't been super on about it (I miss saying on and having people understand that it also means zealous). But today, we voted on changing the gendered lyrics of the Charter song. To me, using gendered terms isn't offensive, but it sounds unnecessarily antiquated. A portion of the club, about 150 of us, sat down and participated in an open moderated debate for and against changing the lyrics of the song. Each point was well made, good considerations were brought up, and important clarifications were raised. Having 150 people discuss a controversial issue openly, calmly and respectfully is not something I see all the time, and I'm super proud of everyone in the club for making this possible.
Rodrigo, the club president (soon to step down for the next president), cried during his last speech. His term was marked by the changes in the member selection mechanism (between a subjective bicker system and an open points system). He cried when he made the point about how our openness and respect makes us special, and even though it was short and to the point, it's one of the most moving speeches I've ever heard.
-----------------
Also, man, facebook is so cool, I really hope I can get in!!!
I'm in Charter Club (one of the eating clubs in Princeton), and honestly, I haven't been super on about it (I miss saying on and having people understand that it also means zealous). But today, we voted on changing the gendered lyrics of the Charter song. To me, using gendered terms isn't offensive, but it sounds unnecessarily antiquated. A portion of the club, about 150 of us, sat down and participated in an open moderated debate for and against changing the lyrics of the song. Each point was well made, good considerations were brought up, and important clarifications were raised. Having 150 people discuss a controversial issue openly, calmly and respectfully is not something I see all the time, and I'm super proud of everyone in the club for making this possible.
Rodrigo, the club president (soon to step down for the next president), cried during his last speech. His term was marked by the changes in the member selection mechanism (between a subjective bicker system and an open points system). He cried when he made the point about how our openness and respect makes us special, and even though it was short and to the point, it's one of the most moving speeches I've ever heard.
-----------------
Also, man, facebook is so cool, I really hope I can get in!!!
Thursday, November 15, 2012
O hai
So many people have actually serious blogs where they blog about one particular thing. In fact, almost everyone I physically meet now who has a blog keeps one where they talk about a topic others might be interested in, like programming or design or startups or law or non-profits. Hopefully people find whatever random thoughts I have to be interesting enough, because I can't be counted on to write anything else here.
-------------------------------------------------
With the obligatory meta-blogging out of the way, here goes:
Thoughts on virtualization:
So I'm currently learning about OS (Operating Systems). One very important thing that the OS does is to give each program* the illusion that it is the only program running on the computer - each program "thinks" it has all 4GBs (or however much) of RAM and the entire CPU to itself even though it's actually sharing those with all the other programs(except the OS kernel) that are running on the computer. How does the OS do it? Well, it turns out that at any one time, the state of a program's execution(called the context) can be stored in quite a small amount of space. Every once in a while, you can "freeze" the program, save the context, "unfreeze" another program, and repeat. In this way, each program gets to run some of the times, and is never aware of anything that happens when it is not running.
But if we stop there, other programs could also leave stuff lying around, which would break the illusion that each program is the only one running. So the OS kernel does something sneaky: it never exposes the actual space to the program. Each program gets a virtual space, such that anytime it looks at or changes something in its space, the OS kernel would give the program the impression that whatever the program is looking for is where the program thinks it showing the program that the corresponding real location contains. The OS kernel has to do this very carefully, otherwise the program would get confused, or even worse, it might accidentally allow the program to touch something it is not supposed to touch.
The nice thing about this world that if the OS is done right, each program doesn't "feel" that their requests take a long time, even though it might actually have taken 1 million times as long as it had ever existed for the request to be fulfilled (I think about that when I'm lining up at the DMV.) The bad thing is that you're all alone, and the only way to talk to anyone else is by making a phone call to "the system".
So suppose you are someone with the ability to stop time and you never die, you could actually give everyone on earth the illusion that they are alone! Freeze time for everyone, let one guy move once in a while, and then put everyone else in a small place, swapping them around from time to time.
Then truly, "Only through ourlove and friendship system calls can we create the illusion for the moment that we're not alone".
* technically it's a process/thread, but the details are not that important here.
Some notes on entropy, and an interesting consequence
Entropy is a measure of "disorder", but it's also useful to think of it as a measure of how little we know about a system - these are equivalent ways of looking at the same thing.
Suppose you have a room full of stuff. The usual thing to say is that a messy room has more entropy than a neat room, because the messy room is more "disordered". But we can also look at this from the information perspective. Imagine you have a robot that can reconstruct your room item by item. Now you tell your robot, "Construct a messy room." (Assume that the robot also understands what "messy" and "neat" means. This would become important later.) How much would you know about the room that has been reconstructed by the robot if you are not allowed to look at it?
Well, not very much, because the robot has a great deal of freedom in putting things in different places. You have no way to know where any particular thing is going to be, and even after you know where something is, you still don't know where all the other things are. You are, in fact, so clueless about the messy room that the robot would need to give you a lot of information before you really know where everything is. In other words, saying that a room is messy doesn't tell you very much about it - that what it means (at least from an information perspective) by high entropy. In contrast, if you told the robot to construct a neat room, you already know that the books would be on the shelves, and the tables and chairs are going to be some angle not too far from being a right angle before you even look at the room - saying that a room is neat tells you quite a bit about it. That's how it's low entropy. Another way of saying it is that, entropy is a measure of the number of ways you can make up something that agrees with a particular description. "Messy room" is less descriptive than "neat room", so there are more ways you can make a room messy compared to the number of ways you can make a room neat.
This ties in two fundamental ideas in physics and computer science together. It turns out that this sets absolute physical limits to the information density of a chip, or anything at all (though in practice, this density limit is about as relevant to chip designers today as the speed of light limit is to spacecraft builders). Here's the argument: suppose you make a chip that holds a lot of information, let's call it an "uber-chip". When I say, "Here's an uber-chip," I am allowing for many ways to make up an uber-chip. Perhaps I flip the last bit, perhaps I flip the middle two, or perhaps I alternate the bits... and so on. This means that chips of arbitrarily high information density also have arbitrarily high entropy. Now, the entropy of a black hole increases by a certain fixed amount when you drop a mass into it. Suppose you drop an uber-chip into a black hole. Well, so you've started with something to arbitrarily high entropy, and how you've converted it to some fixed amount of entropy - decreasing the total entropy of the universe in the process. You can't do that, so that means no uber-chip is possible.
And I think that's pretty cool.
-------------------------------------------------
With the obligatory meta-blogging out of the way, here goes:
Thoughts on virtualization:
So I'm currently learning about OS (Operating Systems). One very important thing that the OS does is to give each program* the illusion that it is the only program running on the computer - each program "thinks" it has all 4GBs (or however much) of RAM and the entire CPU to itself even though it's actually sharing those with all the other programs(except the OS kernel) that are running on the computer. How does the OS do it? Well, it turns out that at any one time, the state of a program's execution(called the context) can be stored in quite a small amount of space. Every once in a while, you can "freeze" the program, save the context, "unfreeze" another program, and repeat. In this way, each program gets to run some of the times, and is never aware of anything that happens when it is not running.
But if we stop there, other programs could also leave stuff lying around, which would break the illusion that each program is the only one running. So the OS kernel does something sneaky: it never exposes the actual space to the program. Each program gets a virtual space, such that anytime it looks at or changes something in its space, the OS kernel would give the program the impression that whatever the program is looking for is where the program thinks it showing the program that the corresponding real location contains. The OS kernel has to do this very carefully, otherwise the program would get confused, or even worse, it might accidentally allow the program to touch something it is not supposed to touch.
The nice thing about this world that if the OS is done right, each program doesn't "feel" that their requests take a long time, even though it might actually have taken 1 million times as long as it had ever existed for the request to be fulfilled (I think about that when I'm lining up at the DMV.) The bad thing is that you're all alone, and the only way to talk to anyone else is by making a phone call to "the system".
So suppose you are someone with the ability to stop time and you never die, you could actually give everyone on earth the illusion that they are alone! Freeze time for everyone, let one guy move once in a while, and then put everyone else in a small place, swapping them around from time to time.
Then truly, "Only through our
* technically it's a process/thread, but the details are not that important here.
Some notes on entropy, and an interesting consequence
Entropy is a measure of "disorder", but it's also useful to think of it as a measure of how little we know about a system - these are equivalent ways of looking at the same thing.
Suppose you have a room full of stuff. The usual thing to say is that a messy room has more entropy than a neat room, because the messy room is more "disordered". But we can also look at this from the information perspective. Imagine you have a robot that can reconstruct your room item by item. Now you tell your robot, "Construct a messy room." (Assume that the robot also understands what "messy" and "neat" means. This would become important later.) How much would you know about the room that has been reconstructed by the robot if you are not allowed to look at it?
Well, not very much, because the robot has a great deal of freedom in putting things in different places. You have no way to know where any particular thing is going to be, and even after you know where something is, you still don't know where all the other things are. You are, in fact, so clueless about the messy room that the robot would need to give you a lot of information before you really know where everything is. In other words, saying that a room is messy doesn't tell you very much about it - that what it means (at least from an information perspective) by high entropy. In contrast, if you told the robot to construct a neat room, you already know that the books would be on the shelves, and the tables and chairs are going to be some angle not too far from being a right angle before you even look at the room - saying that a room is neat tells you quite a bit about it. That's how it's low entropy. Another way of saying it is that, entropy is a measure of the number of ways you can make up something that agrees with a particular description. "Messy room" is less descriptive than "neat room", so there are more ways you can make a room messy compared to the number of ways you can make a room neat.
This ties in two fundamental ideas in physics and computer science together. It turns out that this sets absolute physical limits to the information density of a chip, or anything at all (though in practice, this density limit is about as relevant to chip designers today as the speed of light limit is to spacecraft builders). Here's the argument: suppose you make a chip that holds a lot of information, let's call it an "uber-chip". When I say, "Here's an uber-chip," I am allowing for many ways to make up an uber-chip. Perhaps I flip the last bit, perhaps I flip the middle two, or perhaps I alternate the bits... and so on. This means that chips of arbitrarily high information density also have arbitrarily high entropy. Now, the entropy of a black hole increases by a certain fixed amount when you drop a mass into it. Suppose you drop an uber-chip into a black hole. Well, so you've started with something to arbitrarily high entropy, and how you've converted it to some fixed amount of entropy - decreasing the total entropy of the universe in the process. You can't do that, so that means no uber-chip is possible.
And I think that's pretty cool.
Friday, September 07, 2012
pen it down
It's sometimes a mystery to me why there are so many problems I can ponder in my head that seem as unsurmountable conundrums, only to seem quite simple to resolve once I write them down(or more likely type them out). According to the extended Church-Turing hypothesis, all computable problems can be solved with a Turing machine. And a human brain is surely Turing complete, right? It can simulate a Turing machine by following the procedure step by step. But aha! The assumption of an infinite memory tape is not held! A normal human brain that doesn't write anything down can't store and retrieve arbitrarily long bit strings at will. So an unassisted human brain is not Turing complete. But armed with a recording device - aha! Then the human is Turing complete, and can solve all kinds of (computable) problems.
So I guess when people argue that writing is the greatest human invention, I could supply another (not particularly intuitive) reason to support that argument.
Thursday, September 06, 2012
double happiness!
I'm really happy for my sister. Both my sister and her now-husband are so amazing! I'm glad that things are moving ahead in their lives. I'm also glad that I can now refer to the amazingly intelligent, considerate and decisive (and lucky) Oliver Wicker as my brother-in-law instead of "just" my sister's boyfriend(which has a somewhat transient feel to it, even though they've been together for so long!). And I can refer to Kitty as "my sister-in-law... sort of" instead of the awkward "my sister's boyfriend's sister" which somehow seems more distant than it feels.
During the wedding reception(which was a high tea), I had the chance to sit with and talk to people around 9 years older than me. It's quite remarkable how... "steady" (forgive my diction) they seem! Conversation flows easily and casually even between strangers - they know what questions to ask to simulate a friendly chat, and how to respond in a witty manner. I wonder if it's because they are in the same age group and they have a better idea of what the concerns of people of that age are? Or perhaps making friendly conversation with people they've just met is a universal skill they've acquired over time? That seems like a really useful thing to learn. Sitting at that table I keep feeling that they know a great deal about life that I don't, but they are all pretty cautious about giving advice.
For a while after the reception I felt like I was the most immature of the bunch of people at the reception (well maybe excepting the one year olds), and wondered: Do all x year-olds talk like x year-olds? I don't want to be sound young and immature! Is there any way around it? And my mom told me: It can only come with experience, through success, failure, or even suffering, and all that will take time. Of two people of the same age, one can sound like old when talking about one thing, but he'll probably sound younger when talking about another, as the time they have will tend to equalize the amount of experience they have, and no experience has greater intrinsic worth over another, be it success or failure.
Oh well, I guess I can only wait then!
Wednesday, September 05, 2012
Brought about by change
I just identified the background music in NLB when they announce "Dear readers, the library will be closing in 15 mins, …) it's moonlight sonata!
--------------------------------
Today, when I received some change from a waitress, I was reminded of this story by my primary school teacher: there was once a student who didn't really know etiquette. So everyday, when the student submitted a notebook containing his homework to his teacher, the teacher would toss it aside and walk away without any explanation. This made the student frustrated yet puzzled. Every day he would greet the teacher, or say something nice before submitting his homework, but the teacher did the same thing: toss it aside, and walk away. It was only one day when he finally, by chance, decided to try handing in his homework with both hands that the teacher finally accepted it. So, according to my teacher, the moral of the story is: it's more polite to hand things over with both hands.
But the obvious thing in the mind of the student would be: Why doesn't the teacher just tell me what I'm doing wrong? Perhaps, the student could also have watched how other students were handing in their homework to try to figure out what he was doing wrongly. That reminds me of an article about reinforcement learning vs imitation vs instruction. The article found reinforcement learning to be less effective than both imitation and instruction for a certain task. It makes me wonder: if machines become conscious, would they get frustrated when we try to train them to do something by reinforcement learning? Would they think, "Yeh right, as if you know how to do it!" or "Why don't you just tell me what you want and not make me do this over and over again?"
But I guess there will always be some amount of reinforcement learning to be done as long as there are unsolved problems - some people need to stay at the forefront to do less inefficient learning task of discovering new methods, while others can help to spread the knowledge in a more efficient way by making more people aware of the method, or by teaching it well. Perhaps the moral of the story is that Nature is kinda like that annoying teacher in that story, and we as students should help to make each others' lives a bit easier.
Monday, August 20, 2012
Sunday, December 18, 2011
This is the 500th post! I can't believe that this blog has survived so long. Unfortunately, nothing epic is going to happen here (Then again, 500 is only special because we have 2 hands, 5 fingers, and Indian merchants were smart). This is just a test for a web service called "IntenseDebate", which I think seems pretty cool. Really! Nothing much to see here.
Sunday, November 27, 2011
I do hope that overseas Singaporeans stop giving people the impression that Singapore is a dictatorship/totalitarian/authoritarian/despotic state.
What prompted me to write this post is that some of my schoolmates from USA thought that Singapore isn't a democracy - they were genuinely surprised to hear from me that Singapore holds elections at all. When I asked them, "What gave you the impression that Singapore is not a democracy?" The response: "Even the other Singaporeans whom I've talked to don't seem to think that Singapore is a democracy."
I find it rather curious why some people from the US get the impression from Singaporeans that Singapore is some sort of an outright dictatorship. It is a matter of fact that Singapore is a democracy. Leaders are chosen by elections. Leaders are accountable to the people. Citizens have civil rights. What is left as a matter of opinion is the extent to which the above three are true, and whether that means that Singapore is "truly" a democracy.
I cannot generalize this to all overseas Singaporeans, of course, but from the ~5 Singaporeans whom I have encountered describing Singapore to Americans, I get the impression that they tend to be too eager to state why Singapore is not "truly" a democracy, but forget to mention that Singapore is a democracy in the first place. While another Singaporean will understand that Singapore isn't run by Mussolini/Hilter/Mao, someone who hasn't heard much about Singapore might have a different idea in mind when one says, "Well, we don't exactly have free speech, we are known for really strict laws, and the ruling party has been ruling since independence."
Why do we (the ~5 people we have met and admittedly, myself initially) so spontaneously speak of how Singapore isn't "exactly" a democracy before we even state that it is one? My guess is that Singaporeans are used to talking about Singapore-style democracy in the context where they are arguing about the finer points with other Singaporeans, who are well aware of and are used to all the rights that they have in Singapore. The largely pro-government mainstream media wouldn't hesitate to remind us that the government is accountable to the people. The rulers wouldn't hesitate to remind us that they are, after all, chosen by the people fair and square. The truth is not entirely that. Given these information as the basis to agree upon or to critique, New media and coffee-shop talks balance out the dominant influences of public opinion with a primarily anti-government stance to arrive at something that is more accurate.
The effect of this context of pro-government media is that when discussing Singapore politics, a Singaporean subconsciously assumes that the listener already knows some big things about Singapore. We are already used to doing all kinds of things with few state-enforced consequences, the things that we cannot do without consequences are particularly salient. We pretty much take our rights for granted. As such, we are used to talking about the rights we don't have and how elections aren't exactly fair, rather than the rights we do have.
This works fine in Singapore, because everyone lives here and has some intuitive idea of how "oppressed" we are. But when someone who is used to thinking of and talking about Singapore politics this way will be misleading to people who haven't heard much of Singapore. Without the preconception of all the things you can do in Singapore, it gives a rather negative and inaccurate impression.
I cannot prescribe what one should say to others about Singapore. After all, what I say is also mostly my own opinions. But I do hope that when Singaporeans talk to other people about Singapore politics, do consider that people might assume the worst if you only state what is not good.
PS: Another observation is that Malaysians tend to give a more positive portrayal of Singapore than Singaporeans themselves do. Maybe we can learn from them to produce a more balanced "pitch" about Singapore politics.
What prompted me to write this post is that some of my schoolmates from USA thought that Singapore isn't a democracy - they were genuinely surprised to hear from me that Singapore holds elections at all. When I asked them, "What gave you the impression that Singapore is not a democracy?" The response: "Even the other Singaporeans whom I've talked to don't seem to think that Singapore is a democracy."
I find it rather curious why some people from the US get the impression from Singaporeans that Singapore is some sort of an outright dictatorship. It is a matter of fact that Singapore is a democracy. Leaders are chosen by elections. Leaders are accountable to the people. Citizens have civil rights. What is left as a matter of opinion is the extent to which the above three are true, and whether that means that Singapore is "truly" a democracy.
I cannot generalize this to all overseas Singaporeans, of course, but from the ~5 Singaporeans whom I have encountered describing Singapore to Americans, I get the impression that they tend to be too eager to state why Singapore is not "truly" a democracy, but forget to mention that Singapore is a democracy in the first place. While another Singaporean will understand that Singapore isn't run by Mussolini/Hilter/Mao, someone who hasn't heard much about Singapore might have a different idea in mind when one says, "Well, we don't exactly have free speech, we are known for really strict laws, and the ruling party has been ruling since independence."
Why do we (the ~5 people we have met and admittedly, myself initially) so spontaneously speak of how Singapore isn't "exactly" a democracy before we even state that it is one? My guess is that Singaporeans are used to talking about Singapore-style democracy in the context where they are arguing about the finer points with other Singaporeans, who are well aware of and are used to all the rights that they have in Singapore. The largely pro-government mainstream media wouldn't hesitate to remind us that the government is accountable to the people. The rulers wouldn't hesitate to remind us that they are, after all, chosen by the people fair and square. The truth is not entirely that. Given these information as the basis to agree upon or to critique, New media and coffee-shop talks balance out the dominant influences of public opinion with a primarily anti-government stance to arrive at something that is more accurate.
The effect of this context of pro-government media is that when discussing Singapore politics, a Singaporean subconsciously assumes that the listener already knows some big things about Singapore. We are already used to doing all kinds of things with few state-enforced consequences, the things that we cannot do without consequences are particularly salient. We pretty much take our rights for granted. As such, we are used to talking about the rights we don't have and how elections aren't exactly fair, rather than the rights we do have.
This works fine in Singapore, because everyone lives here and has some intuitive idea of how "oppressed" we are. But when someone who is used to thinking of and talking about Singapore politics this way will be misleading to people who haven't heard much of Singapore. Without the preconception of all the things you can do in Singapore, it gives a rather negative and inaccurate impression.
I cannot prescribe what one should say to others about Singapore. After all, what I say is also mostly my own opinions. But I do hope that when Singaporeans talk to other people about Singapore politics, do consider that people might assume the worst if you only state what is not good.
PS: Another observation is that Malaysians tend to give a more positive portrayal of Singapore than Singaporeans themselves do. Maybe we can learn from them to produce a more balanced "pitch" about Singapore politics.
Saturday, September 10, 2011
Are exclamation marks outdated? CAPS LOCK IS QUITE GOOD AT GIVING THE IMPRESSION OF SHOUTING. In fact, from the first word of the 'capped' sentence that you read, you would already know that there is some shouting going in, whereas if you were reading a sentence that ends with an exclamation mark, you would have no idea that the sentence was meant to be emphasized, leading to only the last couple of marks "sounding louder" in your inner voice!
Tuesday, August 30, 2011
Five minutes
Can I summarize each course that I took last year in about five minutes? Let's see.
Classical Mechanics:
- Principle of Least Action is equivalent to Newton's Laws.
- Principle of Least Action goes like this: there is a quantity called "Action", which is a function of a trajectory(real or hypothetical). Only trajectories with an extremum action are physically possible.
- If you have N degrees of freedom, you can use this principle to write N equations of motion. Just plug the Lagrangian into Euler's equation.
- If there are constraint forces, find an excuse to put the constraint into the Langrangian (by adding "zero" times a Langrange multiplier). The magnitude of the Lagrange multiplier give you an idea of how "strong" the constraint force is.
- You can rewrite the Lagrangian in another form. Applying the Legendre transform gives the Hamiltonian. The point of doing this is to make it easier to express equations of motion in terms of momentum. You also get first order differential equations instead of second order ones. (Doesn't make it easier to solve though, since they are typically coupled for non-trivial cases)
- Noether's theorem - the coolest thing of all. "Every symmetry has a corresponding conservation law." It sounds like something that came out of Dao De Jing (ok maybe not that much). E.g., if shifting your setup in the x-direction isn't going to affect its motion, then this means that x-momentum is conserved. So this theorem links every displacement with some kind of momentum. BUT! The weirdest thing is, time is associated with Energy! Really interesting, and this will become significant later.
- Central force motion and Scattering. Some mathematical tricks, many useful formulae that you probably shouldn't try to derive by yourself during a midterm. Landau is brilliant, read each page many times.
- Oscillations with driving forces, damping forces and coupling. Driving forces - use Fourier transformation for periodic driving forces, use Green's function for the general case, Laplace transform works well too. Damping forces - memorize/refer to solutions of this kind of second order ODE, and be comfortable with complex exponents, trig functions and hyperbolic trig functions. Coupling - make small oscillation approximations, dump it into a matrix and solve the eigenvalue/eigenfunction problem. Maple/Mathematica is your friend. If coupling is weak, approximate generously.
- Non-intertial frames and rigid body motion. Nightmare fuel. Remember Euler's equations, remember how to use them. Developing an intuition, while not wholly rigorous, helps to prevent sign errors and saves time. There's also a magical equation, "d/dt|_inertial = d/dt|_body - omega cross", which nobody seems to know how to derive but somehow works marvelously well.
- Special relativity. The relativistic Lagrangian is -gamma mc^2. You can obtain it by doing a Legendre transform on total relativistic energy. All the above tricks apply, except that rigid bodies aren't so rigid anymore.
Multivariable Calc:
- Langrage multipliers are cool.
- The Hessian determinant is useful for checking whether a stationary point is max, min, saddle, or degenerate. Take note of boundary points.
- The Jacobian determinant is useful for doing multiple integrals. It's important to set the integral up properly.
- Line integrals - find a new parameter to describe the line, and integrate along it. Remember to take the dot product.
- Surface integrals - find two parameters to describe the surface, and integrate along them. Remember to take the cross product. Be careful with the orientation, or use intuition to check the answer and reverse-engineer the sign.
- Curl of grad is zero, div of curl is zero.
- There are three different manifestations of the "fundamental theorem of calculus" - a relationship between differentiation and integration. 1) If the vector field has zero curl, it's possible to express it as a grad of some scalar field. It's the relationship between gradient and line integral. 2) Divergence theorem expresses the relationship between divergence and volume integral. 3) Stokes' theorem expresses the relationship between curl and surface integral.
Social Psych:
- There are different ways of doing social psych research - typically analyzing data and doing experiments. There are advantages and limitations to all approaches. Note experimental biases, cultural differences, observer effects. Studies may be value-laden. They might also be conducted in unethical ways. Most studies quoted in this course are done in the US, so what is true there might not be true elsewhere.
- The "self" is a more fluid construct with East Asians than it is with Americans - i.e., different situations, different "self".
- Many biases - "Better than average" phenomenon is one of them. Tendency to warp perception/interpretation of reality to make oneself feel better.
- Situational influence -> Mechanism --> Phenomenon --> Effect. Two common mechanisms are arousal and rationalization.
- Attitudes influence behaviour, but behaviour can also influence attitudes. Some powerful persuasion techniques make use of this.
- Persuasion could take central route or peripheral route. Which route works better depends on a number of factors.
- Conformity and Obedience - [Asch, Milgram expt] Most people can be made to conform under the right circumstances (though there is always some who don't conform). A few factors that affect the degree of conformity/obedience have been found.
- Attraction - people are typically more attracted to those they meet more often and that they are more similar to.
- People form groups quite easily, and tend to bias against the outgroup.
- Stereotypes influence people's perceptions unconsciously but significantly. Approaches have been found to reduce this.
General computer science(Java)
A bit of the following:
- Elementary types and operations, Arrays, If else, loops, methods and arguments, recursion, classes and objects, scope and encapsulation, using data types, creating data types, linked lists, using interfaces, order of growth(time/resources), insertion sort vs mergesort, computability, tractability, P versus NP.
Writing seminar
- UNCLEAR THESIS/MOTIVE WILL BREAK AN ESSAY
- Read the source before critiquing it (instead of referring to someone else's critique)
- There are ways to twist a quotation to suit your purpose.
- Sometimes there's just no correct answer.
- Good stitching helps to make a essay more "flowy", which is good.
(To be continued)
Can I summarize each course that I took last year in about five minutes? Let's see.
Classical Mechanics:
- Principle of Least Action is equivalent to Newton's Laws.
- Principle of Least Action goes like this: there is a quantity called "Action", which is a function of a trajectory(real or hypothetical). Only trajectories with an extremum action are physically possible.
- If you have N degrees of freedom, you can use this principle to write N equations of motion. Just plug the Lagrangian into Euler's equation.
- If there are constraint forces, find an excuse to put the constraint into the Langrangian (by adding "zero" times a Langrange multiplier). The magnitude of the Lagrange multiplier give you an idea of how "strong" the constraint force is.
- You can rewrite the Lagrangian in another form. Applying the Legendre transform gives the Hamiltonian. The point of doing this is to make it easier to express equations of motion in terms of momentum. You also get first order differential equations instead of second order ones. (Doesn't make it easier to solve though, since they are typically coupled for non-trivial cases)
- Noether's theorem - the coolest thing of all. "Every symmetry has a corresponding conservation law." It sounds like something that came out of Dao De Jing (ok maybe not that much). E.g., if shifting your setup in the x-direction isn't going to affect its motion, then this means that x-momentum is conserved. So this theorem links every displacement with some kind of momentum. BUT! The weirdest thing is, time is associated with Energy! Really interesting, and this will become significant later.
- Central force motion and Scattering. Some mathematical tricks, many useful formulae that you probably shouldn't try to derive by yourself during a midterm. Landau is brilliant, read each page many times.
- Oscillations with driving forces, damping forces and coupling. Driving forces - use Fourier transformation for periodic driving forces, use Green's function for the general case, Laplace transform works well too. Damping forces - memorize/refer to solutions of this kind of second order ODE, and be comfortable with complex exponents, trig functions and hyperbolic trig functions. Coupling - make small oscillation approximations, dump it into a matrix and solve the eigenvalue/eigenfunction problem. Maple/Mathematica is your friend. If coupling is weak, approximate generously.
- Non-intertial frames and rigid body motion. Nightmare fuel. Remember Euler's equations, remember how to use them. Developing an intuition, while not wholly rigorous, helps to prevent sign errors and saves time. There's also a magical equation, "d/dt|_inertial = d/dt|_body - omega cross", which nobody seems to know how to derive but somehow works marvelously well.
- Special relativity. The relativistic Lagrangian is -gamma mc^2. You can obtain it by doing a Legendre transform on total relativistic energy. All the above tricks apply, except that rigid bodies aren't so rigid anymore.
Multivariable Calc:
- Langrage multipliers are cool.
- The Hessian determinant is useful for checking whether a stationary point is max, min, saddle, or degenerate. Take note of boundary points.
- The Jacobian determinant is useful for doing multiple integrals. It's important to set the integral up properly.
- Line integrals - find a new parameter to describe the line, and integrate along it. Remember to take the dot product.
- Surface integrals - find two parameters to describe the surface, and integrate along them. Remember to take the cross product. Be careful with the orientation, or use intuition to check the answer and reverse-engineer the sign.
- Curl of grad is zero, div of curl is zero.
- There are three different manifestations of the "fundamental theorem of calculus" - a relationship between differentiation and integration. 1) If the vector field has zero curl, it's possible to express it as a grad of some scalar field. It's the relationship between gradient and line integral. 2) Divergence theorem expresses the relationship between divergence and volume integral. 3) Stokes' theorem expresses the relationship between curl and surface integral.
Social Psych:
- There are different ways of doing social psych research - typically analyzing data and doing experiments. There are advantages and limitations to all approaches. Note experimental biases, cultural differences, observer effects. Studies may be value-laden. They might also be conducted in unethical ways. Most studies quoted in this course are done in the US, so what is true there might not be true elsewhere.
- The "self" is a more fluid construct with East Asians than it is with Americans - i.e., different situations, different "self".
- Many biases - "Better than average" phenomenon is one of them. Tendency to warp perception/interpretation of reality to make oneself feel better.
- Situational influence -> Mechanism --> Phenomenon --> Effect. Two common mechanisms are arousal and rationalization.
- Attitudes influence behaviour, but behaviour can also influence attitudes. Some powerful persuasion techniques make use of this.
- Persuasion could take central route or peripheral route. Which route works better depends on a number of factors.
- Conformity and Obedience - [Asch, Milgram expt] Most people can be made to conform under the right circumstances (though there is always some who don't conform). A few factors that affect the degree of conformity/obedience have been found.
- Attraction - people are typically more attracted to those they meet more often and that they are more similar to.
- People form groups quite easily, and tend to bias against the outgroup.
- Stereotypes influence people's perceptions unconsciously but significantly. Approaches have been found to reduce this.
General computer science(Java)
A bit of the following:
- Elementary types and operations, Arrays, If else, loops, methods and arguments, recursion, classes and objects, scope and encapsulation, using data types, creating data types, linked lists, using interfaces, order of growth(time/resources), insertion sort vs mergesort, computability, tractability, P versus NP.
Writing seminar
- UNCLEAR THESIS/MOTIVE WILL BREAK AN ESSAY
- Read the source before critiquing it (instead of referring to someone else's critique)
- There are ways to twist a quotation to suit your purpose.
- Sometimes there's just no correct answer.
- Good stitching helps to make a essay more "flowy", which is good.
(To be continued)
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