rohitarondekar

Can somebody in the know elaborate on how far ahead China's lead is in AI?

Would using a dedicated phone number (sim) that is not shared with any other service protect you from this? Basically nobody besides Google and you would know of this number. In India dual sim phones are very common and I've been thinking of getting a second sim (phone number) for this purpose.

I've started many MOOC's but never finished because I couldn't keep up with watching the videos. Not being able to flip back and forth is really limiting. The only courses[1] I've finished had good quality notes and completely depended on them and avoided the lecture videos.

[1]: Roughgarden's Algorithms part I, Programming Languages by Dan Grossman and Machine Learning by Andrew Ng.

For the second return to work doesn't the if have to be an expression i.e return the result of evaluating either y or z as the result of the if expression? If the language has if statements like say Javascript then it won't work.

I'm not well versed with reading research papers etc but I have one question. Could it be possible that by simply practicing mindfulness meditation the brain restructured itself via a placebo style effect rather that because of the meditation itself?

For anybody who has access to the paper what did the control group do during the eight weeks?

This looks good but two things:

1] The guides section is still on the older design which I'm guessing will be updated later?

2] IMHO on the show gem page the authors/owners section should be moved below licence + versions/runtime-deps sections. The later are more important for first time scanning especially when looking for a new gem.

Probably a precursor to Play Store Movies: https://play.google.com/store/movies

I tried posting these to HN some time back but the submission didn't gain any traction. Glad to see it pop up on front page of HN today.

Great advice. I'd also recommend the Compilers course on Coursera. Although it is already underway, you can take the self paced version. https://www.coursera.org/course/compilers

I don't think that is entirely true. I've met really nice Ruby developers and know many online (twitter/github/irc etc) who are really nice and welcoming and always want to help. Of course there will always be loud and obnoxious people in a programming community but so far I've honestly haven't met a single such person.

What exactly was the point of this blog post? Quite a few of those reasons are valid and none of the arguments against the 10 reasons are good. It reads like "OMG BUT RUBY! MY PRECIOUS!!1"

This is actually very useful and Symbian (Nokia N73) alarm app also used to do this! Saved me many times from setting wrong alarms. :)

The article doesn't actually provide any significant reasons as to why you need to be a polyglot programmer. If anybody is reading this I would love if somebody can provide reasons besides being able to think differently. I'd like to encourage programmers, at a ruby user group, to learn other programming languages. But besides the think differently I can't come up with any compelling reasons. Am I being silly? Is being able to think differently about problems the only reason to learn different programming languages?

I think everyone of us should try and specialize in at least one thing. That does not imply that you do your best to know nothing about relevant fields. For example if you are a web developer who works on Ruby on Rails and makes awesome web apps but don't like working on the front‒end, i.e HTML/CSS/JS then that is OK as long as you have some basic knowledge about those technologies and respect those who do work in that area.

Back to the specialization, I really think you should have at least one area in your chosen field where you have deep knowledge. How deep? On the above example - maybe you know internals of Rails + Rack very well. If you are on the front‒end may be you should have a thorough understanding of how browsers work, how HTML/CSS is parsed and rendered etc. I don't really have a good explanation as to why this is important but I've noticed that the really good web developers or designers tend to have at least one specialization or deep interest within their fields.

(1) Syntax wise Ruby is a lot easier and more expressive than Scala. IMHO I feel that Ruby is an OO language with some functional sprinkles while Scala is a functional language with OO sprinkles.

(2) Ruby has a great ecosystem if you are building web apps. It's also got a lot of testing libraries. :) But in seriousness the number of libraries in non web/tooling space is slowly increasing as faster Ruby implementations have become a focus point. Also JRuby allows you use the vast ecosystem of Java from within JRuby.

(3) Performance wise I'm pretty sure Scala will outperform Ruby. I don't think JRuby will be able to compete either. Charles Nutter, JRuby Core developer wrote this blog post which explains why Ruby is hard to optimize ― http://blog.headius.com/2012/10/so-you-want-to-optimize-ruby...

Of course take everything I've said with a bag of salt! :)

If you are interested in reading papers then you might want to follow http://twitter.com/onepaperperday

You might also want to use a tool like Mendelay. It works on Ubuntu too and lets you store papers online and sync. Plus a whole lot of features.

I am interested in reading papers to improve my knowledge and have already started hoarding papers. It requires some discipline though especially if you are not used to reading technical papers. I wonder if there is scope for a Google Group to read and discuss a paper every week or month or twice a month. :)

You mean set x0 to 1, right?

People who do linear regression at work don't add a x0 feature? During the lecture the prof. only said that adding a x0=1 for all samples m, is by convention and helps simplify the computation. Unless I missed something during the lecture that's the only explanation that was given.

Can you please explain why this is? Or maybe point to an explanation somewhere? Thanks.

This was shown by Professor Andrew in the Coursera ML class that's happening right now.

Given n features x1 to xn we introduce x0 feature which is always set to 1. During the Regularization lectures the professor said that we don't need to control (or regularize) the theta0 (the parameter for x0) because it doesn't make a difference. I believe this is the reason W(0,0) is set to 0.

The lectures are a little light on the maths, i.e the professor explains only enough maths to explain the techniques so I'm not aware of more details. I'm planning on watching some Linear Algebra lectures to fill in the gaps. :)

Re: Invertability, according to the professor, if lambda is > 0 then the matrix will be invertable. Again I'm not 100% sure if this is true or not.

Thank you for explaining, I think I get it now. The ML course on Coursera is a little light on the Maths. As in the professor only explains as much is needed to perform the techniques. So I think I'll be watching Strangs Linear Algebra lectures on OCW soon. :)

According to Wikipedia[1]Matrix Inversion is also O(n^3) and according to the note can be even better by inverting smaller matrices within and multiplying[2].

My linear algebra isn't very good so I'll have to look into LU Factorization but is there vast difference between the computational performance of the two operations? (Assuming you don't need solve Ab=c for different values of b and c)

Also is LU Factorization used often in machine learning instead of inverse?

[1]: http://en.wikipedia.org/wiki/Computational_complexity_of_mat...

[2]: Because of the possibility to blockwise invert a matrix, where an inversion of an n×n matrix requires inversion of two half-sized matrices and 6 mulitplications between two half-sized matrices, and since matrix multiplication has a lower bound of Ω(n2 log n) operations[17], it can be shown that a divide and conquer algorithm that uses blockwise inversion to invert a matrix runs with the same time complexity as the matrix multiplication algorithm that is used internally. source is [1]

You can use the same techniques used in Linear Regression (with multiple features) to do Polynomial Regression. For example suppose you have two features x1 and x2, you can add higher order features like x1x2 or x1^2 or x2^2 or a combination of these. While doing linear regression you treat these terms as individual features so x1x2 is a feature say x3. This way you can fit non-linear data with a non-linear curve. However there is a problem of overfitting, i.e your curve may try to be too greedy and fit the data perfectly, but that's not what you want. So Regularization is used to lower the contributions of the higher order terms.

Wikipedia has an article on Polynomial Regression: http://en.wikipedia.org/wiki/Polynomial_regression

P.S I'm doing this course https://www.coursera.org/course/ml so my knowledge may not be entirely correct so take everything I've said with a pinch of salt. :)

As pointed out by Tony Arkles in blog post comments, GSL is a bit restrictive in it's licensing:

  GSL can be used internally ("in-house") without restriction, but only redistributed in other software that is under the GNU GPL.

http://www.gnu.org/software/gsl/

In computing (X^TX)^(-1) if the number of features is large then it can be slow as computing the inverse of a matrix is slow. Also unless you use pseudo inverse (pinv in octave) you need to take care of degenerate cases. However if you use Regularization i.e replace the (X^TX)^(-1) with (X^TX + lambda*W)^(-1), where lambda is the regularization parameter and W is a matrix of the form:

  |0 0 0|
  |0 1 0|
  |0 0 1|

i.e identity matrix with (0,0) set to 0

This ensures that the matrix is now invertible. Regularization takes care of overfitting.

P.S I'm a ml n00b doing Machine Learning course on Coursera so I might be unaware of more practical knowledge of the above. :D

Are there any UX or usability studies regarding date time formats to use on the web? I'd be interested in knowing more than this feels right to me. :)

Interesting. I'm just going on a hunch here, but maybe getting better photographs of the Mars surface is not a priority anymore? From the wikipedia page of Mars Science Laboratory the goals of the mission are:

To contribute to these goals, MSL has six main scientific objectives:

* Determine the mineralogical composition of the Martian surface and near-surface geological materials.

* Attempt to detect chemical building blocks of life (biosignatures).

* Interpret the processes that have formed and modified rocks and soils.

* Assess long-timescale (i.e., 4-billion-year) Martian atmospheric evolution processes.

* Determine present state, distribution, and cycling of water and carbon dioxide.

* Characterize the broad spectrum of surface radiation, including galactic radiation, cosmic radiation, solar proton events and secondary neutrons.

By those I can understand why carrying a high res camera was not a priority because it would have added weight, taken up space and also consumed more bandwidth while transmitting? :)

Try to get into a bugmash of some kind. I started this way with Rails and I wrote about it http://www.rohitarondekar.com/articles/my-first-rails-bugmas...

Many companies and tech groups have these around the world during meetups and conferences.

But most importantly dont let this pull request fool you. Rails is nice to contribute to even if you are starting out and the rails core team especially jose valim and santiago pastorino are super helpful.

I think he meant

    [ u s e r @ma c h i n e E x amp l e ] $ . . / mo n o r a i l . j s i n s t a l l mo o t o o l s

Switched to using Opera Mini Next. I don't like the social home page but it can be switched off. The speed dial looks really nice and over all the browser is responsive. Great work as usual from Opera! Allows my aging Nokia N73 to browse the web in a sane way.

I agree. I just hate to see this ― "zomg bundler sucks at <some feature usually speed>! I hate using it! It has to be fixed for me!"

Any open source project needs help. The maintainers of Bundler have 200+ issues on the issue tracker. If people could help them replicate and confirm issues, write failing tests and if possible write patches ― it would do a world of good. But instead it's EASIER to complain and whine. So...