"'Principal Component Analysis' is a dimensionally invalid method" - <AUTHOR> http://www.amazon.com/review/R16RJ2PT63DZ3Q/ref=cm_cr_rev_detmd_pl?ie=UTF8&asin=0521642981&cdForum=Fx37214P6NH2KSB&cdMsgID=Mx19BAIRVRARPZV&cdMsgNo=1&cdPage=1&cdSort=oldest&cdThread=Tx2OVZUUHW9MMJ9&store=books#Mx19BAIRVRARPZV <comment><USER2> There is actually a fix to this problem in classical statistics (as far back as Pearson in the early 20th century) if the object is to perform PCA on data matrices: Don't use the covariance matrix for PCA. The issue of units is only a problem if you're using a matrix that has units itself. This problem is readily solved by using the correlation matrix instead, which is dimensionless by definition. The downside to this circumvention is that you have essentially re-weighted each of your variables, so the weight contributed by each variable is more similar. This may not be what you want.

If PCA is not being used to reduce the dimensionality of multivariate data, this might be invalid. There are other uses of PCA besides working on data (that image reduction technique using SVD comes to mind) that he might be addressing.

If you want a treatment of PCA in a respected text (at least by the statistical community--not sure what the ML people think ;) ), look no further than Hastie, Tibshirani and Friedman's Elements of Stastical Learning.

[http://www.stanford.edu/~hastie/local.ftp/Springer/OLD//ESLI...](http://www.stanford.edu/~hastie/local.ftp/Springer/OLD//ESLII_print4.pdf)

<comment><USER3> > The downside to this circumvention is that you have essentially re-weighted > each of your variables, so the weight contributed by each variable is more > similar.

Is this similar to "whitening"?

<comment><USER2> It is somewhat similar. The procedure I describe is normalizing (using z-scores instead of raw data) the data. The difference, as far as I can tell, is that normalizing retains the correlation structure of the data, while whitening uncorrelates the observations. R is the lingua franca of the academic statisticians, so you might not derive a huge amount of value from this, but this question was asked a couple years ago on Stats.SE: [http://stats.stackexchange.com/questions/53/pca-on- correlati...](http://stats.stackexchange.com/questions/53/pca-on-correlation- or-covariance)

</comment></comment></comment><comment><USER4> This kind of complaint applies to _any_ method. Dimensional analysis just means that your data satisfies a certain kind of symmetry. A scaling symmetry in this case. It doesn't matter how long you define one meter, as long as you do it consistently. Hence any answer should not depend on the length of a meter. There are other symmetries, for example it does not matter where you put 0 on the temperature scale. Hence your answer should not depend on where you put that zero (unless that zero has special significance in your context). This is a kind of additive symmetry. Another additive symmetry is that it shouldn't matter which year you call year 0 (unless it has special significance, e.g. you are investigating the birth of jesus). In the same way your data can have any kind of symmetry, especially with multi-dimensional data you often get extra symmetries. For example it shouldn't matter in which direction you define north and east.

For any given problem, you should generally only use methods that obey the symmetries that your data has. This doesn't mean that PCA is invalid as a method, it's just only valid on a data where the scaling symmetry does not apply. Another example would be fitting a line through the origin for temperature data. That's invalid, because the result you get depends on where you define your zero (but as before, it might be valid if that zero has special significance in your context). Does that mean that fitting a line through the origin is invalid for any data set? No.

In other words, the same criticism could be applied to any given method. Just choose any symmetry that the method does not respect, and then declare it completely invalid. Hence we cannot dismiss a method outright purely based on this reasoning. For example PCA is perfectly valid on unitless data. What's even stranger is that the author does like neural neworks, which are certainly not dimensionally valid, heck they probably don't satisfy _any_ real world symmetries. This is also a case where it can be OK to use a dimensionally inconsistent method. As long as it works, it works.

<comment><USER5> In addition to unitless data, PCA works when all of your variables have the same dimension. It simply doesn't make sense to build a principle component vector that is a mixture of (i.e. weighted sum of) vectors with non-identical units.

</comment></comment><comment><USER6> _If you change the units that one of the variables is measured in, it will change all the "principal components"!_

So what ? The same is true of most machine learning methods including neural networks and SVM's, you just have to use the same units consistently.

<comment><USER7> Wrong.

Neural networks are affinity invariant. You can rotate, skew, translate the input data however you want, the optimum stays the same. Same for SVMs.

<comment><USER6> But the weights will be different, which it seems to me is comparable to saying that the principal components change.

</comment></comment></comment><comment><USER8> Maybe I'm having a brainfart or something... but since PCA is eigenvector/eigenspace-based and essentially determines linear noncorrellation of the different vectors, changing units of measurement shouldn't change which dimensions are most different about said vectors?

Edit: Ah right - <http://en.wikipedia.org/wiki/Whitening_transformation> \- let covariance matrix be I.

<comment><USER9> That's what I thought when I read this, but I haven't looked at PCA in awhile, so I wasn't sure. It's only relative differences on each axis that matter, right?

<comment><USER10> No.

PCA tries to project to the subspace that preserves as much distance in the input space possible. If you multiply a coordinate in the input space by a factor of 2, it will contribute relatively more to the distances, and hence change the fitted projection beyond just a scaling factor.

<comment><USER11> So we're talking about a very general problem. When I noticed that a system of equations including x=y can have a different least-squares solution when you change it to 2x=2y, I was quite surprised.

</comment></comment></comment></comment><comment><USER12> Lots of kinds of analyses require some kind of normalization or whitening to work properly.

The problem with PCA is that everyone knows about it and kind of understands it, and thinks that it'll magically tell them something interesting about their data. Especially when you can take the first three components and make cool-looking 3D plots...

</comment><comment><USER13> > If you change the units that one of the variables is measured in, it will > change all the "principal components"

By the way that's worded, it sounds like a case of sensitivity rather than the method. If you change one of the variables to a unit that is way out of scale, then it's quite possible that the results of PCA, and many other methods, will change. But that's because it's not scale invariant, and so if you want good results you need to present your variables in the same units, and/or in some normalized format (zscored, etc.) where the scale of one unit doesn't blow the others out of the water.

These methods are not magical, and they are not intelligent. They do not know what they're looking at, so it's your job to feed them something reasonable.

That said, if you take some physically grounded data and change units, you won't recover different eigenvectors as long as your input data is good. The physics doesn't care about the units, or the coordinate system, or whether you use python or anything else.

<comment><USER6> _if you take some physically grounded data and change units, you won't recover different eigenvectors as long as your input data is good._

I don't think that's accurate. Consider a set of points distributed along a line in 2D. If you do PCA on these points you will find that the 1st eigenvector points along the line and the second is orthogonal to it.

If you now rescale the axes so that x is measured in meters and y in light years the slope of the line will change and so will the the 2 PCA eigenvectors.

However the relationship between the 2 eigenvectors and the distribution of the data points will remain the same. The first eigenvector will still point along the line and the second will still be orthogonal to it.

In machine learning one is interested in the distribution of the data not in whatever units they happen to be measured in, hence I don't understand MacKay's objection.

<comment><USER14> The mathematical way to state this is that a choice of units is equivalent to a choice of an inner product in linear algebra( or, more generally, the choice of a metric tensor in differential geometry). Basically, the choice of an inner product defines what it means for something to be orthogonal in a space.

Principal component analysis is predicated on a choice of inner product, since component directions are always chosen to be orthogonal. It's not clear what orthogonality could mean in a 2D plane where one direction is measured in inches and the other in tons, so naive PCA isn't appropriate in such a case.

Others have mentioned in this thread that "whitening" the data before PCA fixes this problem, by removing cross-correlations. Presumably, in that case, the notion of orthogonality is taken from the statistical properties of the data. (Maybe it normalizes physical units like inches to the standard deviation of the data's distribution in inches?)

</comment></comment></comment><comment><USER15> In practice if you're working in high dimensions and don't do PCA then you have very little chance of building a good model. It certainly isn't linearly valid if to you valid demands scale invariance, but it's an essential tool for unsupervised feature engineering.

<comment><USER16> I definitely agree that you need dimensionality reduction, though there are methods other than PCA (e.g. auto-encoders.)

<comment><USER17> Auto-encoders have some big advantages over PCA, but they suffer the same shortcoming (sensitivity to units of measurement) described in the original post.

<comment><USER3> In practice you have to scale data to [-1,1] or [0,1] for a neural net anyway, right? (Depending on the kernel function.)

<comment><USER16> Another common method is to scale to mean 0, variance 1. In my opinion this makes more sense since it handles outliers a bit better-e.g., consider a case where most of your values for a feature are scaled from 1 to 10 but there's one point with value 1,000,000.

<comment><USER17> I agree that you SHOULD normalize/scale data before running neural networks and autoencoders.... and this resolves the units issue in most cases (unless measurements in some units are non-linear functions of measurements in others).

But this scaling also resolves the issue for PCA. So, I don't see much difference between autoencoders and PCA with regards to original post's "dimensional invalidity" concern.

If anything, the scaling options you mention suggest "dimensional invalidity" isn't a big deal in practice for either method.

</comment></comment></comment></comment></comment></comment><comment><USER18> Wouldn't readers be better off if the author wrote about this problem with PCA in the book, instead of ignoring it entirely?

<comment><USER2> While I agree with you, if the author believed the entire method is invalid in all situations, he could make a strong argument that it wasn't worth the space to put it in at all. It would be a long book if it was filled with all the methods currently in production that did _not_ work!

<comment><USER14> PCA extremely widely known and (ab)used. You can't justify ignoring it.

</comment></comment></comment><comment><USER19> "X is a ... method that gives people a delusion that they are doing something useful with their data." could be applied to pretty much any method in ML if you don't know what you're doing. PCA is a strange omission, but it's not like it's hard to find references on it. ITILA is a great book and it's legally free online, by the way.

</comment><comment><USER20> If anyone is interested, PCA is used in scale development to help reduce the number of items down to something useful. It is typically followed by a factor analysis to determine factors, though far too many use PCA in place of a factor analysis. I didn't realize it was used much outside of measurement.

<comment><USER13> PCA and other similar forms of dimensionality reduction are used all over the place, from healthcare to control systems to financial analysis. These days it is most often used as a preprocessing step for some other analysis routine, though.

</comment></comment><comment><USER21> In data compression, there is what is called the Karhunen-Loeve or Hotelling transform. It's essentially an alias for "Principal Component Analysis".

The Hotelling transform is interesting in that it achieves optimal energy compaction, but has little practical value since it needs to be constructed anew for each dataset (usually, images).

Just to pull your thoughts away from massive, unfiltered big data :)

</comment><comment><USER22> I wish that someone would inform the field of psychology about this. Principal Component Analysis is often a way of simply reifying your prejudices.

</comment><comment><USER23> So what alternative method of dimensionality reduction does the author recommend?

Considering that PCA works fine in the case that the dimensions form a proper vector space (e.g. geometrical space, stock market returns, temperature, etc, etc ,etc), it seems questionable to completely dismiss such a useful and historically important method.

</comment><comment><USER24> Open Matlab and type

        load hald;
        coeff = pca(zscore(ingredients))
        ingredients(:,1) = ingredients(:,1) * 2;
        coeff = pca(zscore(ingredients))

Magically, you get the same result regardless of if you change the units of one variable.

<comment><USER2> Yes, of course you will--because you've normalized the data. If you had run PCA on just ingredients instead of on the normalized ingredients, I would imagine the results would be different. I can't verify since I don't have matlab on this computer, but doing PCA on raw data with one set of units will produce a different PCA doing it on data with another set of units.

<comment><USER24> Yes, you get different results if you don't normalize. My point was, I don't see why "you have to trivially normalize your data first" is a meaningful argument against anything.

<comment><USER2> Because normalization reduces the influence of variables that have a higher variance. In raw data, if you have marathon times and heights for runners in a race, and you measure the times in minutes and the heights in inches, the influence on the principal components from the times will likely be much more.

Like all problems in statistics, it ought to depend on the specific task at hand. If there is some a priori reason to use the original scale (or a different re-weighting), it ought to be used. In general, PCA on correlation matrices is much preferred for exactly the reason you mention.

</comment></comment></comment></comment><comment><USER25> I'm still waiting for Information Theory to be updated with the errata I submitted. In at least two places (pages 458 and 459) he mentions the possibility of accepting (!?) the null hypothesis.

snark.

<comment><USER26> What was your replacement suggestion? I would say acceptance is often a fair description for lack of rejection.

<comment><USER25> The null hypothesis is never accepted. You can fail to reject the null, but this is entirely different from accepting it.

If you claimed to accept the null in an intro statistics class, you'd probably be failed.

<comment><USER26> That's an extremely dogmatic position. There are certainly situations where it is not useful or even accurate to proceed under the null hypothesis, but the converse is also very much true. Checking Wikipedia, I see they also describe the scenario as "accept or fail to reject".

If you want to argue for why "accept" is materially different from "fail to reject", feel free to do so - but I suggest that the chasm is by no means wide.

</comment></comment></comment></comment><comment><USER27> You can always make variables in any system non dimensional. The whole field of chemical engineering works on this principle. Once you do that, you are free of irregularities/issues that stem from scaling.

Apply PCA after non dimensionalizing any system. Read More here : <http://en.wikipedia.org/wiki/Nondimensionalization>

</comment><comment><USER28> Yes, this is a well known problem with PCA. So often we just whiten (<http://en.wikipedia.org/wiki/Whitening_transformation>) the data first.

<comment><USER6> Whitening and (full rank) PCA use the same linear transformation except whitening scales the eigenvalues so all axes in the transformed system have unit variance.

In other words whitening the data before applying PCA should result in the same eigenvectors expressed in the original coordinate system.

<comment><USER28> Yes, but I think for many places where PCA is used, we are precisely interested in which eigenvectors have the largest eigenvalues. The scaling beforehand makes a unit change less likely to effect which eigenvectors are the most important.

<comment><USER6> But once you know the eigenvectors the eigenvalues (and hence their distribution) are determined, again in the original space.

On the other hand if you're talking about the eigenvalues for the whitened data they're all 1.

So I'm still not seeing what whitening adds to PCA.

Just rescaling each dimension of the original space so that all dimensions have unit variance, without doing any rotations, may change things, but I don't think that's what is usually called whitening (according to Wikipedia).

<comment><USER29> You are absolutely correct, and your interlocutor is mistaken to use a whitening transformation before PCA.</comment></comment></comment></comment></comment>


Brief Meditative Exercise Shown to Improve Cognition - <AUTHOR> http://www.sciencedaily.com/releases/2010/04/100414184220.htm

<comment><USER2> _"Participants were randomly assigned in approximately equivalent numbers to one of two groups, one of which received the meditation training while the other group listened for equivalent periods of time to a book (J.R.R. Tolkein's The Hobbit) being read aloud."_

So does this mean that meditation helps cognition, or listening to "The Hobbit" hurts cognition?

</comment><comment><USER3> The meditation I do is being aware of one's awareness. Its the simplest. Notice the awareness that is reading this post. This is the "awareness of 'you'". Also, called the "I am".

Its impact is profound. After a while, you realize that thoughts and your identification with a person arises out of this simple silent awareness. Thus the constant stream of thoughts related to "I" arise from this silence.

I am thus this pure awareness, not the mind or personality that I thought i was. The identification with the mind-created story crumbles and with that a huge amount of suffering, longing, craving etc. The freedom experienced is immense.

Once starts freeing from the mental conditioning that has happened since birth, so relationships, decision-making etc improve.

One can put one's mind to one task without thoughts interrupting. Also, a lot of inessential tasks, time-wasters etc have also dropped off. One can focus on important activities.

</comment><comment><USER4> Talk about synchronicity...I started meditating regularly for the past four weeks at multiple intervals for about 15-20 minutes per day (average about 1 hour total per day). The results have been astounding, especially when it comes to my perception of time: all of a sudden, I have more of it. A day seems like a day instead of a few hours, and all of a sudden, a week is a long period of time.

I believe this is due to increased levels of concentration (as indicated by the article).

</comment><comment><USER5> "mindfulness meditation" = vipassana

<http://news.ycombinator.com/item?id=587032>

</comment><comment><USER6> Every religion has some form of meditative practice (though some are less advertised than others - I never did hear about Jewish meditative practices until I was deep into Buddhist practices). And for the non-religious, there are folks like John Kabat-Zinn (see link below) who take a more scientific approach.

<http://www.mindfulnesstapes.com/> (I have not used these but it was a decent enough link to give an overview)

<http://www.umassmed.edu/behavmed/faculty/Kabat-Zinn.cfm>

</comment><comment><USER7> "The meditation-trained group averaged aproximately 10 consecutive correct answers, while the listening group averaged approximately one."

I call bullshit. Normal untrained adults would do far better than this on adaptive n-back. If this is true, it means sitting and listening to Tolkien is more damaging to your working memory than having a screwdriver jammed into your prefrontal cortex.

<comment><USER8> There is something off; I'm not sure what the article is talking about.

The study is available from <http://groups.google.com/group/brain-training>

Reading it, I see significant advantage for the meditating group on the 'Computer Adaptive 2-back task', but not the 1 v 10 difference cited. Specifically, it seems that according to figure 1, before the intervention, the average 'extreme hit rate' on the n-back was ~2 for the meditating group and ~3.5 for the Tolkienists, but after 4 sessions, the meditating group was scoring >9 while the Tokienists were ~5.

The only significant discussion of the 2-back is on pg 6:

> "Fig. 1 shows the significant group by session interaction found in the > analysis on the extended hit rate from the computer adapted n-back task, > F(1, 47) = 6.76, p = .01, g2 = .12. The meditation group, in contrast to the > control group, had more extended hit runs. There was also a significant > session effect, F(1, 47) = 18.78, p < .001, g2 = .29. Follow-up analyses on > the speed measure of the n-back task did not show any evidence of an > interaction effect F < 1, or an effect of session or group, Fs < 1."

</comment></comment><comment><USER9> Another interesting experiment would be to have a group, instead of meditating, listen to, for example, a lecture about a topic that interests them.

I wonder if the control group had heard The Hobbit before.</comment>


Most common mistakes during interviews - <AUTHOR> https://aitorvs.github.io/post/most_common_mistakes_during_interviews/ <comment><USER2> "Who comes to an interview for a tech company not having done tons of leetcode problems, studying algorithms and data structures to the limit?"

Most normal developers. Spending you time on leetcode means you want to get in a faang. Most people are going for other roles.

<comment><USER3> Eh IDK. Leetcode type questions are starting to slip into many industries and types of companies. I recently interviewed at large finance (not trading firms, retail banking/investment) and insurance companies. They both asked LC medium/hard.

I was honestly taken a back. These companies aren't known for "high" standards and make up for the lack of interesting work with WLB (or at least it comes across like that.

Just like how everyone copied google Qs a decade ago (how many toothpicks can a tree yield...). I'm fully expecting everyone to copy FAANG like interviews because someone in HR thinks it might signal better hires, and why wouldn't you want better hires right?

<comment><USER4> So if they ask the same questions at Google and same at BigInsuranceCo, why work for a lower salary at BigInsuranceCo.

If the interview is the same, you are better off working at some one who pays better. As a side effect eventually there could across the board better pay.

<comment><USER3> That's what I'm wondering myself. I've been taking more time to adequately prepare for faang, because as you said why not work for the company that pays more if the interview is nearly the same?

</comment></comment></comment></comment><comment><USER5> This post reeks of elitist/holier-than-thou attitude that the whole industry has unfortunately been feeding into. I also suspect that it is why there's so little diversity in tech and why there's this absurd notion that there's not enough "qualified" candidates to fill positions.

1) is something that I abhor because it allows the interviewer to assume very little of the responsibility for communication, which is an exercise for both people to come to a consensus of what the task is at hand. Instead of saying "did I communicate this effectively", it's saying "it's the listener's fault for not understanding me."

2) is very similar to 1) in that it also absolves the interviewer of any responsibility for communicate. It's also an absurd proposition because it's saying it is the interviewee's job to keep me, the interviewer, entertained. This is absurd because the purpose of interviews is to vet a candidate, if that's not the purpose, then the interviewer should make it more clear that an hour's worth of a jester's time is being requested.

3) is specifying a criteria that might make sense for recent college graduates or if the candidate knows what to prepare for. In my experience, no such guidance is typically given, the most I've seen is "prepare for questions that might be relevant to the role/job posting." The interviewer fails to consider does he/she have a full time job? Did the interviewer actually provide materials for he/she to study? If the questions the OP cited were not actually provided, how do they know to prepare for those types of questions.

<comment><USER6> I think the point is that you can't control the interviewer, only yourself, so concentrate on what you can control.

I think you're taking an overly unfair view of what the author meant.

<comment><USER5> Then you're saying, "the system is broken, just live with it."

We know what's wrong with that statement in this climate.

<comment><USER6> So if I decide to change my own behavior rather than trying to change my spouses behavior, it's because I'm really saying the marriage is broken?

That's a non-sequitur.

</comment></comment></comment></comment><comment><USER7> How useful are interviews in general? I've been led to believe that an interview is a very poor indicator of future performance[0], and that an interview biases the hiring decision in typically negative ways.

[0] [https://80000hours.org/podcast/episodes/will-macaskill- moral...](https://80000hours.org/podcast/episodes/will-macaskill-moral- philosophy/)

<comment><USER8> I've recently started doing interviews for my company, and while there are definitely candidates that we have been on the fence about accepting that would probably have been a great fit, in the end, the false positive rate is more important to us than the false negative rate. Maybe we missed out on some great candidates but the criteria we used to evaluate them also allowed us to avoid a lot of very bad candidates. The perfect interview process doesn't exist, we have to make do with the fact that whatever the interview process is, we will miss out on great candidates and end up making an offer to candidates that will not work out. But indeed: for candidates, this means that you shouldn't take rejections to heart too much: you might have been a great fit for the role and a bad fit for the interview process. If you're consistently getting rejected for positions for which you believe you are qualified, maybe you need to get better at interviews, or maybe you're not as qualified as you may think.

<comment><USER9> > If you're consistently getting rejected for positions for which you believe > you are qualified, maybe you need to get better at interviews, or maybe > you're not as qualified as you may think.

This comment represents everything that is wrong with your technical interview process. Big yikes.

<comment><USER6> agreed.

The lack of self-awareness displayed by that comment is kind of impressive. Especially the bit about being so keen on identifying "bad" candidates, not realizing that the entire point is that interviewers are actively bad at determining good vs bad candidates.

</comment></comment></comment></comment><comment><USER10> Really nothing I haven't read before. Apparently these are all mistakes a _candidate_ can make.

I would appreciate it if companies finally acknowledged that interviewing is a two-way street.

I have cancelled way more interviews due to red flags happily waved by companies than companies have rejected me because I failed one of the 8 algorithms questions.

<comment><AUTHOR> I agree with that comment. I have a part 2 of the blog post where I address the issues I have seen in interviewers

[https://aitorvs.github.io/post/most_common_interviewer_mista...](https://aitorvs.github.io/post/most_common_interviewer_mistakes/)

<comment><USER10> This adequately represents the 1:1 experience of one technical interview.

Let me cherry-pick an example: You mention that you don't read a candidate's CV before your one interaction with them (the technical interview). As you say, this is a debatable choice (I find it somewhat acceptable).

At that point, has anyone else at your company read the candidate's CV and cover letter? Sounds stupid, but you would not believe how many people ask about specific topics ("So have you worked with a relational database before?") not in order to ask deeper questions about knowledge or experience, but just in order to tick off checkboxes on their HR form. (This is not made up, this has actually happened to me.)

This bigger issue of a company never asking themselves "How do we as a company show that we actually give a shit about each candidate, and are not just looking for a butt in an office chair" is where in my experience, _lots_ of companies are still completely failing at self-reflection.

<comment><USER11> > At that point, has anyone else at your company read the candidate's CV and > cover letter? Sounds stupid, but you would not believe how many people ask > about specific topics ("So have you worked with a relational database > before?")

My understanding is that this situation happens as a test to see that you were the one that wrote your resume.

<comment><USER10> Huh, I didn't think this would be common enough for companies to start testing against.

Thanks for the insight!

<comment><USER11> It's not just a tech-worker thing, I remember being warned about knowing exactly what's on your resume in highschool ~15 years ago.

</comment></comment></comment></comment></comment></comment><comment><USER12> > #2 - Not keeping your interviewer engaged > It is extremely simple, just > think out loud

Yes, "think out loud" is better than being completely silent, but given that many hiring decisions are based on how the interaction feels, including the quality of the communication _in order to assess thinking skills_, candidates can see huge returns by learning specific communication techniques.

I make videos on this topic (technical and non-technical interview and negotiation skills), and happened to have just made a video on what to say while writing code:

[https://www.youtube.com/watch?v=sv42PpY- nK8](https://www.youtube.com/watch?v=sv42PpY-nK8)

<comment><USER13> Noting that I had a really intense negative emotional reaction to this video. It's possible that I'm just not your target audience, and certainly the depth of response felt... disproportionate, but I thought I might share my reaction in case it was useful to you.

I think there was a combination of things that straight away disposed me negatively towards it - the negative title (stop X!), the negative introduction (stop x, again) and also the camera being so close to your face. It had the effect of feeling like I was being simultaneously negged and mansplained to by some overly aggressive dude (no doubt more an artifact of my own life experiences more than the video. Stop telling me what to do, Dad.). It felt very you-tube, but like, the uglier parts. I stopped watching pretty quickly.

Glancing at your profile, it seems like you have a number of videos titled "Stop X". I'm noting here that you describe this video as "a video on what to say while writing code." There's a clear value prop there: What to say when writing code! But it doesn't exactly come through in the first exposure to the video. I'd watch a video on "what to say while writing code" because I have my own opinions on it, and am interested in comparing my mental model with someone else who's spent time thinking about good communication in a coding context. Feeling scolded by said video made it a solid pass.

I think I read something purporting to be research about how closeup pictures on faces tend to elicit stronger emotional reactions.

I did like that you were modeling perspective taking - "your interviewer is a programmer who can read your code." Building a capable theory of mind is long term work, and it's work that people who are drawn to computers often don't do.

Anyways, thanks for sharing it, and taking the time to make those videos. It seems like a worthy project.

</comment></comment><comment><USER14> Preparing for interview?

I tend to avoid it except things that are "obvious" but I tend to forget, like you know - there's SOLID and everybody understands it differently and applies it differently, I never remember the theory behind it.

I believe going without preparation means that you're "pure" \- you're talking only about stuff you know or understand, not just seen 10h ago on some blog.

When it comes to questions I really love open questions like design something or try find security issue

<comment><USER15> I think the most valuable preparation you can do is asking yourself long and hard what the other side is looking for, and what you bring that they might be looking for.

This is valuable for yourself as well, because you can avoid places where the role they have in mind for you doesn't fit your expectations

</comment></comment><comment><USER16> I agree with this, and I want to add to #3.

When you prepare for the behavioural questions, give answers of real situations that you are very familiar with, and avoid "keyword soups". I've seen quite a few candidates failing interviews because they gave almost canned answers that seem to hit all the right points, but once you dig deeper they aren't able to elaborate more.

</comment><comment><USER17> Most tech interviews especially for engineers are a one-sided power dynamic that does nothing except make the candidate nervous and eventually rejects them arbitrarily. The ones that do get a job seem to think that that's the only way to interview people and this cycle continues. What happens is this becomes a boys club that excludes anyone else.

<comment><USER18> This is more apparent for people with anxiety too. My mind shuts down during whiteboarding, yet people generally seem to think I'm smart outside any of those scenarios.

I've already been employed for several years at different places, doing a whole range of things, and it's weird that I have to practice some arbitrary exercises in order to demonstrate to a company that I can work. This has led to me landing at companies that don't require the bizarre jumping-through- hoops that filters for the desperate and "committed".

And so far, I've not only yet to see interview-style programming on the job, I've seen utterly atrocious practices.

<comment><USER19> I work for a FAANG company. The interviews were quite stressful, and my goal for every question was to push through and at the very least make some progress instead of giving up.

I don't make use of any of the algorithmic skills I was interviewed on, but I do have to push through stressful situations regularly and make progress in a timely fashion. I do think that if I weren't able to do that during an interview situation, I wouldn't have been able to do that on the job.

Maybe I wouldn't have any stress in my current position if I were 10x smarter or 10x more experienced/knowledgable, but that would also indicate that I were underleveled.

I'm certain there are many smart and skilled individuals that wouldn't be able to consistently make it past a tech interview loop unless they put in lots of "unnecessary" extra work.

<comment><USER20> > I do have to push through stressful situations regularly and make progress > in a timely fashion.

You mean like everyone else in (almost) every single job ever? Do you think developers at inferior companies just sit around blissfully typing away with half of their brains shut off?

Those interview processes say practically nothing about candidate's fit/performance for the job. This has been shown to be true many times. The awkward hoops put in place just result in the interviewer having ample convenient opportunities to turn down a candidate for any reason. Like maybe in the back of their mind, deep deep down inside, they actually _don't_ want to hire that black person who just wasted weeks or months of their life grinding useless leetcode questions.

<comment><USER19> There's stress everywhere, agreed. In my experience, holding all else equal the amount of stress you have is correlated with the cost of screwing something up or of not delivering on time. Holding all else equal, that is also correlated with compensation, and if stress is too high relative to compensation that either means you're getting a bad deal or you're in over your head.

> Like maybe in the back of their mind, deep deep down inside, they actually > don't want to hire that black person who just wasted weeks or months of > their life grinding useless leetcode questions.

That's a reason to push for standardized interviews with objective questions, so you decrease the effect of interviewer bias and focus on candidate performance.

There's definitely something to be said here though about increasing the knowledge of how to get into top tech companies for disadvantaged groups, because I don't think it's common knowledge.

</comment></comment></comment></comment></comment><comment><USER21> In my experience this article applies very well to competent small and medium sized companies. My experience with large companies with names like Floogle or Gloomburg is that the interviewer is just blindly looking for you to read their mind and is irritated with any clarifying questions.

</comment><comment><USER22> Ah, this topic always seems to stir the pot around here. I think these are decent call-outs from the point of the interviewer, so I'll add a couple of my own from the point of a candidate:

1) not screening the company during the interview 2) not preparing by doing "warm-up" interviews for roles you won't be too sad about if you don't get 3) not doing enough interviews to get multiple offers for negotiating leverage

For my first point, you'll learn a lot about the company and how they work from the interview process. If the company has dysfunctional elements to its corporate culture, depending on the size, it's quite likely they'll be surfaced here. Not only is this one of the first impressions of you for them, but it's one of the first impressions of them for you. Pay attention to what your gut and intuition tell you here. Every time I've broken this rule, it's bitten me.

For my second point, I think that people often forget that the only way to get better at interviewing is to just do it over and over again. It's a little hard to do that in a synthetic environment because it's hard to trick your brain into behaving as if it is real unless it actually is. But wait, you may say, treating an interview like practice is unethical! But I'd disagree. After all, if you really do well on the interview but you're not chomping at the bit to join, they might be more willing to negotiate and make you an offer that would make you reconsider. But, you likely know (and can force-rank) the roles you'd be most willing and least willing to take if you had the opportunity, so make sure to go through the sequence from least desirable to most desirable so that you have more leverage.

My third point is probably the most crucial. You need the BATNA (best alternative to negotatiated agreement) of accepting something else or staying where you are to be able to negotiate. Otherwise, you have much less leverage. This is part of why timing and interviewing for less desirable roles is preferable, because you are more likely to negotiate with an offer for your more desirable role by the time you get there.

<comment><USER23> > screening the company during the interview

Can you offer any advice or resources on what to ask or watch out for in this area?

<comment><USER22> That's hard to say. It feels a lot like dating. First of all, you want to avoid lemons. Secondly, you want to avoid glaring mismatches, so things can at least work out and be sustainable. But there sure are a lot of places where mismatches can occur!

Beyond company fit, there needs to be team fit (and proximally manager fit) and role fit. A lot of this depends on size, too. Company fit is going to be really important if you're anywhere early. But beyond a size, it matters a whole lot less than manager+team.

For the latter, you have to work with the team and manager on something to get a sense of what their style is and whether you'll clash. Try and find some way to talk about a problem as if it's a real world scenario, and see how easy it is to intellectually collaborate towards a solution. Does it feel natural or no? Would you trust this person enough to work with them for 8H+ a day? Keep this in mind as you compare offers.

But it's hard. You can only discern so much, and this stuff is really easy to fake in an interview. You see different shades of people once you really have to rely on them in the dint of production. This is part of what makes warm intros so powerful -- if you've worked with someone you trust and respect before, and they've worked with someone they trust and respect before, it's more likely that you and that other person will transitively be compatible. Move too far outside that transitivity and you're taking existential risks. This is why it's not always a bad thing to move around a bit more in your earlier career -- it can open up your second degree circles a bit more once you hit mid career.

</comment></comment></comment><comment><USER24> Another of the most common errors is to lie or to exaggerate in a side work experience. If it's catch, it will jeopardize the interview.

A common example is to fill the CV with buzzwords and when asked about them, the knowledge varies from shallow to non existent.

<comment><USER25> Résumé: "Achieved state-of-the-art classification accuracy on MNIST dataset by implementing a residual attention convolutional neural network with Keras and TensorFlow on Google Cloud Platform"

Reality: shift-entered my way through an interactive tutorial in Google Colab's free tier like I was button-mashing a videogame combo

</comment></comment><comment><USER26> > Not keeping your interviewer engaged

Ugh. I'm going through the interview process right now and this peeves me so much

The presumption that I, the supplicant, need to be interesting and keep the interviewer, who has deigned to give me 30 minutes of their time (often 23 minutes because, "sorry I'm late but I also have a hard stop at the top of the hour") "engaged" makes the interview so lopsided, awkward, and just nonproductive

That being said: > Not preparing for the interview

Is completely legit. I have walked out of a couple of interviews wishing I had prepped a little bit more so that I could make the conversation a productive one

</comment><comment><USER27> Regarding 2, I would simply solve it, and then maybe ask about using the same number twice to fine-tune the solution.

In real-world problems I almost always think of corner-cases. So I think that the interview process is flawed - at least in my case - by assuming that not asking about specifics generalizes.

In general, if the interview process is designed in a way that reading a random article like this on HN helps you pass it, I'm kind of skeptical how well it's measuring future job performance.

</comment><comment><USER28> Are algorithm interviews just a legal loophole? They allow companies to do something that is nominally illegal: discriminate against candidates with anxiety disorders and women.[1]

[1] [https://news.ncsu.edu/2020/07/tech-job-interviews- anxiety/](https://news.ncsu.edu/2020/07/tech-job-interviews-anxiety/)

<comment><USER6> It's not possible to avoid "discrimination" against people with anxiety disorders, it's the nature of their disorder.

It's a bit like saying the NBA shouldn't discriminate against short people. At the end of the day, the best performers tend to not be short, that's just reality.

In the same way that anxious people tend to struggle in an interview. Obviously you shouldn't be going out of your way to discriminate, but the reality is what it is.

<comment><USER29> The study suggests how to control for performance anxiety in interviews. Why do you believe it's not possible?

NBA scouts evaluate how players perform in real games. Most tech interviews are nothing like the job.

Many countries require employers to reasonably accommodate people with disabilities. Not going out of your way to discriminate isn't enough.

</comment></comment></comment><comment><USER30> 'Ask clarifying questions' and 'think out loud' are also two of the suggestions in this excellent video from Google showing an example of a great technical interview: [https://youtu.be/XKu_SEDAykw](https://youtu.be/XKu_SEDAykw)

</comment><comment><USER31> > can I multiply a number by itself

This is a great clarifying question. Ambiguous from the prompt.

> what shall I return if there are multiple numbers meeting the criteria

This is a decent clarifying question. I think it is better expressed as a clarifying point instead of question--mention to the interviewer your thinking out loud; something like "if there are multiple options, I'll return an arbitrary pair". Ask if they are okay with that.

> is the list sorted

If I were the interviewer, this question would almost make me dock points off of the interviewee. Maybe not that strong as I do try and ensure people are as comfortable and open as possible in asking clarifying questions, but this barely qualifies as a clarifying question in my opinion. It is almost irrelevant to the prompt; if the lists were sorted and the interviewer failed to mention / there was some "trick" that they expected you to clarify, that would be an awful interview question.

That being said, overall agree with the sentiment and yes you should try and always ask clarifying questions and ensure you understand the problem statement.

<comment><USER32> Asking if the list is sorted was also the very first question that popped up in my head, because it makes the difference between a linear and a quadratic algorithm. Contrary to, for example, having the choice between an n log n algorithm and a linear algorithm, when given the choice between a _quadratic_ and a linear algorithm, it is very rare that the right choice is the quadratic algorithm. (Semi-related: [1])

(EDIT: after thinking about this more than two seconds, the quadratic algorithm for unsorted input can become n log n by sorting the list, though that takes linear space. This would certainly be a clarifying question.)

The other questions would be less obvious to me, though I'd encounter them while thinking more than 2 seconds about the problem, I suppose.

Or maybe this just outs me as an ex-amateur competitive programmer :)

[1]: [https://accidentallyquadratic.tumblr.com/](https://accidentallyquadratic.tumblr.com/)

<comment><USER31> And if you had a magical oracle that spat out the two numbers if a solution exists, and otherwise told you no solution exists, you would have an O(1) solution.

Just because you can ask a question whose answer makes a drastic difference between the best algorithm involved, doesn't mean it is a good question.

(and note I said "_almost_ make me dock points...". And if the answer to the question was "yes, the list is sorted", I would _certainly_ dock points off of the interviewer/company if I were the interviewee for not giving that context).

</comment></comment></comment><comment><USER33> I like that there are no 10 points and boring conclusions chapter

</comment><comment><USER34> Great list. Adding one of the most common mistakes I see during interviews:

Not saying "I don't know" when you clearly don't know the answer to a question.

</comment><comment><USER35> I would say: budget your time.

Try to ask: how many exercises do you have to solve, and how many parts does the current exercise have.

</comment><comment><USER36> Prior to getting an interview you read the job ad. They want original, problem solvers, dynamic, goal-oriented etc. etc.

I've always wondered why they don't somehow all me to demonstrate this before it gets to an interview. Let the candidates winnow themselves out. It could be so easy, it should work, but they don't. IDK, perhaps it works only in theory.</comment>


Barack Obama: Now Is the Greatest Time to Be Alive - <AUTHOR> https://www.wired.com/2016/10/president-obama-guest-edits-wired-essay?mbid=social_twitter <comment><USER2> This is basically the thesis of Hans Rosling's 2006 Ted talk* . Things, on average are better.

What bothers me about this way of measuring progress is that for some, e.g. drug addicted or abusive families, people living in war torn regions, things are not better. For some, things are bad and have been for generations.

For this reason I try to refrain from "things are better" rhetoric, because it feels cruel to those people. Like I'm saying "I know it's bad for you, but I don't really care because it's better for many".

And personally I think from a moral standpoint we have the same responsibility to lift up the bottom as we do to lift the average. The trouble is people at the bottom are often at the intersection of multiple intergenerational disadvantages, which makes helping extremely difficult.

It's exactly this reason that I think it's so important not to say "things are better" without qualifications. If we can't help these people, the least we can do is acknowledge their situation.

* [https://www.ted.com/talks/hans_rosling_shows_the_best_stats_...](https://www.ted.com/talks/hans_rosling_shows_the_best_stats_you_ve_ever_seen)

<comment><USER3> I think the better approach is to highlight progress. Sure, many people still live in difficult situations, but overall, we've made a lot of progress over time.

<comment><USER4> The single, biggest problem is that the progress isn't being shared.

In all first world countries wages are stagnant, housing is completely unaffordable, education is a luxury rather than a right and the rich are getting richer and worst of all more brazen e.g. Rich Kids of Instagram.

<comment><USER5> The Western countries are not a uniform block. Many European countries have free or affordable colleges. Wages are not stagnant in Germany. Housing is affordable in many places, including USA except for a few coastal cities. Etc.

</comment></comment></comment></comment><comment><USER6> This sentiment coming from Barack Obama plays directly into Peter Thiel's claims that the liberal elite are ignoring the plight of so many Americans. The fact that nearly 50% of the population support Donald Trump and his message "Make American Great Again" should make that clear.

See Thiel's pro Trump speech from this afternoon: [https://www.youtube.com/watch?v=AfYLEPRiIyE](https://www.youtube.com/watch?v=AfYLEPRiIyE)

<comment><USER7> Trump is a salesman. He's pretty successfully selling the idea that America used to be great and that he's just what you need to make it great again.

Regardless of whether it's wrong or not, it certainly doesn't have to be true for it to sell. Americans especially seem to love buying hot air.

Now, to address your point, ask yourself if the same class of people you claim Obama is ignoring would have been better off 50 or 100 years ago.

<comment><USER8> Spoken like someone who lives in a different country and is unfamiliar with the nuances of current American political sentiment, which is the reason why Trump's pitch is resonating with just about half of the USA.

Trump connects with Americans on many issues that either affect regular people or make them feel disempowered...loss of jobs, national debt, corruption in Washington, illegal immigration, excessive warfare in foreign lands...it's a little silly to say he's totally full of hot air.

If you don't have a sense for the zeitgeist, you can never understand why a populist is, well...popular.

<comment><USER9> It's resonating with white identity politics. No magic here. It's white nationalism. Sugar coating follows:

<comment><USER10> Which mirrors what has been happening in Europe for a while now.

<comment><USER4> Mirrors what is happening in all Western countries e.g. Australia.

Right wing politicians are exploiting the population around the world by blaming migrants/refugees for all their problems.

<comment><USER11> What benefit does the migrants/refugees bring?

<comment><USER12> What benefits do migrants bring to a country? Immigrants of some sort probably do most of the menial tasks that the vagaries of which uterus you emerged from let you avoid. They're also the doctors who treat you, your coworkers if you're in tech like most of us are, the people who cook both whatever trendy food you enjoy and whatever comfort food you enjoy. They're the people who actually believe in the fictions the West tells itself about what it is and what it wants to be. They're the people who work twice as hard as you do because they actually know the value of what you were born with and never appreciated like they did.

<comment><USER13> If we strip your comment from the emotional affect, you're essentially saying that immigrants are happy to do menial jobs that the locals do not.

How do countries without large immigrant (I won't even go to refugees) populations handle this? Switzerland seems to be doing fine. Japan isn't falling apart because there's nobody to cook. Most of Asia is doing fine without allowing any immigrants.

So on a strict analysis of whether immigrants are beneficial to the host population, your argument isn't made.

<comment><USER12> Did you actually look at information for either of the countries that you cited? Immigrants make up 20% of Switzerland's population. ([https://en.wikipedia.org/wiki/Immigration_to_Switzerland](https://en.wikipedia.org/wiki/Immigration_to_Switzerland)). Japan's economy has been struggling for years now ([http://www.wsj.com/articles/why-japans-economy-is- laboring-1...](http://www.wsj.com/articles/why-japans-economy-is- laboring-1459929574)), and their population is aging at a rapid rate, compounding the economic stagnation, something immigration helps to combat ([http://qz.com/173379/immigration-is-saving-the-us-from-an- ag...](http://qz.com/173379/immigration-is-saving-the-us-from-an-aging- crisis/)).

<comment><USER13> 1\. I don't think of foreigners who live in Switzerland as 'immigrants' (despite the article calling them that). They are foreigners who are residing in the country (and most of them come from Europe anyways). It's extremely hard to obtain Swiss citizenship.

2\. All the talk about Japan economy doing badly is nonsense. If you believe that narrative (which is totally understandable as that's the conventional wisdom), I strongly suggest you read this article: [http://www.nytimes.com/2012/01/08/opinion/sunday/the-true- st...](http://www.nytimes.com/2012/01/08/opinion/sunday/the-true-story-of- japans-economic-success.html)

Basically many Japan watchers (ie people who live there and know the country intimately well) subscribe to this 'alternative' view.

<comment><USER12> So your response is:

1\. Some inconvenient Swiss immigrants aren't immigrants.

and

2\. Read this article from 2012 and ignore the last 4 years of Japanese GDP. ([http://www.tradingeconomics.com/japan/gdp](http://www.tradingeconomics.com/japan/gdp))

Care to try again?

</comment></comment></comment></comment></comment></comment></comment></comment></comment></comment></comment></comment><comment><USER14> All these advances in medicine are great; It's so wonderful to know that rich and powerful people like Obama and Hillary Clinton will live to be 150 - I'm so happy for them - With all the stress I'm under, I'd be surprised if I make it to 50. Maybe the elites can harvest my organs when I'm gone; it's nice to give back to this wonderful society that the elites have created for us.

Yes, social media is great; I have lots of friends on Facebook! Except that in real life I can't even see them because I had to move to a different country to escape the high property prices and high cost of living... And I'm actually one of the lucky ones - Most people don't have the option to work remotely and are stuck paying half their income in rent.

I can't even buy a house because some reserve bank somewhere will mess with the interest rates and cause another housing crash (at the most inconvenient time possible) and I'll have to declare bankruptcy and watch the big banks reprocess my home.

Regarding global warming - I don't care about it at all! With the way things are going, AI will probably destroy us before global warming ever becomes a problem (and by 'us', I mean 'those who are not elites').

<comment><USER5> 50 years ago, the notion of moving to a different country and still being able to work remotely was science fiction. Now it's not only possible, but it's not a crazy luxury -- you're saving money by doing it! And you can still keep up with your friends using a free global network and all sorts of options for video conferencing. (Remember when international phone calls cost many dollars a minute?)

This all sounds like amazing progress to me.

You complain that you "can't" buy a house because something might happen to interest rates at some point. Guess what -- it's always been like that. Housing loans come with risks, and renting has always been relatively expensive for low-income workers. Nothing new under the sun.

I challenge you to point out an era in human history when the élite was less powerful than it is today. The primary reason why it seems that they're gaining in wealth is increased visibility and transparency brought on by the global network -- again, progress.

<comment><USER14> My point is that happiness is not about material things; it's about doing what you want to do - Not what you have to do.

There is a difference between doing something because you want to versus doing it because you have to. I'm not saying that I'm not responsible for my own decisions, but I certainly feel like my hand was forced to some extent.

When I think about people who are less fortunate than me, I think the feeling of powerlessness must be 100 times stronger - Most of these people aren't even aware of what's happening to them.

</comment></comment></comment><comment><USER15> I guess this article is part of the democratic campaign, in which the obamas are the shining beacons. The US president may know better than anyone if his country is in its best state ever, but the rest of the world is not. My country greece has not seen bodies of drowned refugees being washed in our shores since 1922. It's a shocking reality that we never expected we 'd see. The US campaigns in the surrounding region have been failing so abysmally and for so long that we, as a globe, have acquired learned helplessness with regards to wars. War is not the only possible answer to everything, and when its used, it must be used wisely. For that reason alone, i hope trump's inward-looking, anti-inverventionist agenda wins.

</comment><comment><USER16> Bullshit. The 90's were much greater. People had money to spend their way into economic growth that was measureable at the street level. And "asset based recovery" was a term yet to be coined.

</comment><comment><USER17> "That's one reason why I'm so optimistic about the future: the constant churn of scientific progress. Think about the changes we've seen just during my presidency. When I came into office, I broke new ground by pecking away at a BlackBerry. Today I read my briefings on an iPad and explore national parks through a virtual-reality headset."

Those changes are relatively minor.

<comment><USER18> Which raises the question: What _was_ the most significant scientific discovery during the Obama era? Can we even quantify it yet?

<comment><USER19> Deep learning

</comment></comment></comment><comment><USER20> >> Once-quiet factories are alive again, with assembly lines churning out the components of a clean-energy age.

Has he been to the rust belt? How can he say that with a straight face?

<comment><USER2> There needs to only be two examples for the statement to be true. I know of Tesla's Fremont factory, I'm assuming there is another?

<comment><USER21> Some examples here:

[http://www.newyorker.com/business/currency/why-donald- trump-...](http://www.newyorker.com/business/currency/why-donald-trump-is- wrong-about-manufacturing-jobs-and-china)

</comment></comment></comment><comment><USER22> I agree that more funding in science and technology is what we need. But Barack Obama had more in common with the status quo than with what his commentary is suggesting.

There also seems to be a disconnect between what is being said in this article versus the reality. Yes there have been improvements in crime and poverty perhaps, but the quality of employment, the quality of general life for the average person in the West seems to have only degraded in the last decade or two.

I would also argue that the pace of technological advancement has decreased. Despite on-going advances in computer science, we have stalled in many other fields since the end of the cold war, in particular space.

<comment><USER23> > quality of employment, the quality of general life for the average person in > the West seems to have only degraded in the last decade or two.

can you cite some data sources for that claim?

<comment><USER24> You wanted to understand why a Trump supporter is voting for Trump. The Trump support tells you of his experience and why he is voting for Trump. You then demand scientific data to back it up. You are not even listening to what he has to say, and you are not listening to his experience. And this is why you can never understand why he is voting for Trump.

<comment><USER22> I just want to point out I'm not a Trump supporter, in fact I'm in Canada so I cannot vote in the US election. My original comment was just a general observation.

</comment></comment></comment></comment><comment><USER25> Can he be please be President for the next 4 years as well?

regards the rest of the world

<comment><USER26> That's what's crazy. Some of the US wants Trump to be president, 99% of the world doesn't. What's the disconnect?

<comment><USER24> >What's the disconnect?

The millions of immigrants who have to leave their homes because of Hillary and Obama's failure in the Middle East probably don't want any more of that incompetence.

<comment><USER27> What were they supposed to do with Arab spring? They didn't intervene. Should they have intervened?

<comment><USER24> Many failures. Not all failures.

</comment></comment></comment></comment></comment><comment><USER28> It sure beats being in Europe 100 years ago.

<comment> ryan-allen Or Syria now.

<comment><USER29> Or Libya now, to name another country improved by our esteemed Nobel Peace Prize laureate.

</comment></comment></comment><comment><USER30> ...unless the military of the USA has decided that you need to be annihilated via drone strike.

The man commands more violence than most of us can comprehend. It feels out of place for such a person to tell the rest of us how great things are going. The cost of progress of the United States is measured in human lives and the ones doing the killing are the ones deciding it is justified. That's some nasty accounting.

<comment><USER31> I wonder how those drone strikes, and other violence commanded by Obama, would register on a graph like this:

[http://knowmore.washingtonpost.com/2015/05/29/heres-how- many...](http://knowmore.washingtonpost.com/2015/05/29/heres-how-many-people- have-died-in-war-in-the-last-600-years/)

or this

[http://ourworldindata.org/wp- content/uploads/2013/06/ourworl...](http://ourworldindata.org/wp- content/uploads/2013/06/ourworldindata_wars-after-1946-state-based-battle- death-rate-by-type.png)

<comment><USER30> Yeah, I forgot, justice is statistical.

<comment><USER31> The real world kind of is. I'd prefer a president to have the good sense to use military approaches that cause the least amount of deaths. Statistics is a good way of making rational decisions rather than basing them purely on emotion.

<comment><USER30> Like most people, you've found a way to rationalize the violence of your government away as necessary, realistic, justified, pragmatic, etc. Everyone has their own words that magically make killing OK.

Entire families of civilians have been destroyed by drone strikes. There is no evidence for the efficacy of drone strikes. There is no evidence that the military actions the USA has taken in recent decades has been at all worthwhile. The people who decide it is justified are the _same people who commit the violence_.

If it were American families being destroyed all of a sudden out of the sky with no justice or recourse, I think, perhaps you would sing a different tune. Or, perhaps, the death of a few Americans is easily rationalized away. After all, you can just look at the statistics.

[http://engl210-deykute.wikispaces.umb.edu/file/view/omelas.p...](http://engl210-deykute.wikispaces.umb.edu/file/view/omelas.pdf)

<comment><USER31> Ok. Vote for Trump. Maybe he'll be better.

<comment><USER30> You're kidding, right?

There's a reason why the entire political infrastructure of United States can only produce 2 competitive candidates, both of whom are fully in support of global neoliberalism. Yes, if my politics had to be constrained by a system that is specifically interested in denying me alternatives that would challenge its hegemony, then I would pick Clinton over Trump.

But I don't have to. I can say that the whole thing is a rotten mess. Because it is. Eating shit because the chef only serves shit and worse shit isn't rational or realistic. It's just eating shit.

And there will be people who continue to die in order to uphold this hegemony, and so long as they are unimportant people that can be written off as statistical inevitabilities of rational decision-making by the people who benefit from their suffering, I suppose the system will continue receiving the support of people like you?

The thing that puts me off most about mainstream politics is how easily everyone who accepts the system (that includes liberals and conservatives and a whole spectrum of people who accept the basic tenets of the system) writes off the deaths of others. Just what makes you so qualified to rationally decide which deaths are acceptable and which aren't?

<comment><USER31> On the one hand, I'm not a fan of the two party system, I've done tons of work on that and spent tons of time trying to find solutions that may actually take hold before I die.

As for "what makes me qualified"....well, I'm a citizen in a democracy, and therefore my opinion counts. I'm glad I don't have to make those tough life and death decisions directly, but I am glad someone is doing it and they don't have a "burn it all down" attitude, nor do they have such a black and white view of morality that they are unable to do the best thing for us.

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER32> Poverty is down absolutely, but never have it been so high relatively. Rich people never lived so well and poor people never struggled so hard to try to live 1/10 of what money provides today. People don't feel less poor when they have a 2000' car and everyone in Instagram has a brand new.

</comment><comment><USER33> Ok. Obama. Thanks as always.

</comment><comment><USER34> Is president taking credit for successes of private enterprise?

</comment><comment><USER35> People do not respond to authenticity. Obama was the greatest president of my generation, and from the looks of it, that is not going to change anytime soon.

</comment><comment><USER36> Wow, lots of bitter conservatives in here. I thought HN was smarter than that.

<comment><USER37> values != intelligence</comment></comment>


"Only Men Need Apply": Gender Discrimination in Job Advertisements in China - <AUTHOR> https://www.hrw.org/report/2018/04/23/only-men-need-apply/gender-discrimination-job-advertisements-china <comment><USER2> Given the demographic skew from the old policies, a policy of encouraging women to focus on getting the population back to gender parity (and to employee otherwise destabilizing males) might make sense.

I doubt that this problem is the result of such an effort, though. :(</comment>


Lots of Americans can't find US on a map. Not surprised about Fox News on Egypt - <AUTHOR> http://plixi.com/p/73294801 <comment><USER2> Having worked in television news, I can give testament that these maps are, with no exception that I can think of, generated by a dedicated software package. Graphics people figured out a while ago that everybody needs maps, and reinventing them is completely ineffective.

As an example, weather maps at my station were generated by a relatively standard package running on IRIX. News maps were generated by a Web service, one of my first introductions to SaaS. I believe Chyron bought it. The service was stupidly simple - insert coordinates, draw labels, push Submit, receive pictures. I only saw it used, but I know it did the labeling for you.

I know it's fun to beat up on Fox News, but the likelihood of someone moving Egypt's label over Iraq in Photoshop after the fact is far higher than Fox News actually airing this graphic.

<comment><USER3> I just Googled "Fox News Egypt map" and it looks like this is something dredged up from 2009.. It sad that so much of the political dialog in this country is petty gotchas and bickering, instead about issues and governance.</comment></comment>


Ask HN: How many startups fail because of code base issues? - <AUTHOR> How many startups will fail as a result of having poorly written code and as a result it prevents them from growing when they need to pivot the most? <comment><USER2> This is a pretty complicated question, because once you already have traction, a poor-quality code base is not going to stop you from succeeding, it'll just mean that your engineers curse you out for making their lives difficult and occasionally your users curse you out for bugs or scalability problems. Much of Google's early code is a mess (strangely, its post-2007 code is much cleaner, and yet many people think its post-2007 products are lamer), and I've heard Twitter and Facebook both have steaming piles of shit for codebases, though perhaps they've recently been cleaned up.

However, if you _don 't_ have traction, having poor-quality code can make it impossible to add the necessary features/bugfixes that get you there, and can make it impossible to attract and retain the engineers that can do that. I worked at a startup once that died from this; we had a product that our one salesperson had no trouble selling, a prototype that worked great at demos, but we couldn't make it robust enough to launch a v1.0 that we could in good conscience charge for before running out of funding.

However, if you focus on writing good-quality code, you are _not_ focusing on the product, which also will prevent you from adding the necessary features, polish, whatever that will get you to traction. I founded a startup once that quietly died from this; it had a pretty innovative architecture and a relatively clean codebase, but wasn't really useful for users because I spent too much time refactoring and not enough building & polishing.

Basically, you have to realize that you're gambling. Your goal is to put a usable product on the market. Every bit of code you write gets you closer to this, but also increases the difficulty of writing further code. Every bit of time spent refactoring makes it easier to write further code, but is time not spent improving your product. If you spend too much time writing features and never clean up code, it becomes impossible to deliver further features. If you spend too much time refactoring and never deliver new features, you lose out on the market to other companies that were willing to play a bit more fast and loose. Wisdom is figuring out a balance between them.

<comment><AUTHOR> Your reply really helped. I asked because Im in a position where the company is 4 years old, they got initial traction. At this point they want to pivot though, but the current code base does not allow for that because it cannot support the new features.

<comment><USER3> How big a pivot are we talking? Totally different product?

</comment></comment></comment><comment><USER3> The codebase itself isn't the problem, really.

What happens is your engineering talent--if you have any to speak of--starts to get really pissed off that they've had to repeatedly cut corners and now are being expected to save the day. This causes lots of stress, and the more experienced the engineer the more likely they are to either ragequit or make large compensations demands. It's not that the cutting corners is what bothers them...it's that the other folks so badly misjudged the business that the cutting corners was ineffective.

Alternately, a competitor is able to look at your product, build a better architecture, and just plain kick your ass because it's more extensible and they can ship faster. I don't have any good examples for this offhand.

As nostrademons points out, though, you can get farther with a good sales team and a shit codebase than with no sales and a great codebase. _Lots_ of examples of that (including my previous startup).

</comment><comment><USER4> I can't really say but it's my impression that the problem is marketing rather than engineering. I'm thinking specifically of Live Picture, which didn't know how to price its product, nor how to compete with its direct competitor Adobe.</comment>


Ultralight IKEA-Bag Backpack - <AUTHOR> http://sandiegomitch.com/backpacking.html <comment><USER2> What an amount of negativity!

This was clearly done as a DIY project, I love it! It's definitely not worth the time/money, but isn't that the definition of a hobby?

I'm very happy for OP, I always enjoy checking out projects like this: the computer made of marbles, the big CPU made from logic gates, esoteric programming languages... More content like this, please!

<comment><USER3> DIY stuff is cool and this project definitely is. Just understand the limitations of it and use it in situations where it is safe and logical to do so.

<comment><USER4> I feel like that's inherit to the term "Do it yourself" and I'm not sure why people feel like they need to explain it every time someone has a DIY project.

<comment><USER3> Because it is worth discussing what is and isn't good about something? Just blindly saying "cool beans" isn't really a fun discussion at all. And if a topic wasn't meant to be discussed, it shouldn't have been posted to a message board.

<comment><USER5> There is definitely some unnecessary negativity though.

Some comments often miss the problem the inventor was trying to solve when they pick holes.

The most useful criticisms was the comment about the material degrading in sunlight because of uv. Useful thing to know.

</comment></comment></comment></comment></comment><comment><USER6> Whats up everyone. I am the maker of the website and the backpack.

This was my first sewing project, but it turned out much better than I expected.

I loaded the pack with 30 lbs to test it out before I take it on a multi day trip, and it had no problems.

I'm currently working on moving my images to a remote site so wish me luck on keeping the site up.

<comment><USER7> I love this project. Post it to [http://www.ikeahackers.net/](http://www.ikeahackers.net/).

<comment><USER6> Done! Sent them my info.

Feel free to share my website anywhere

</comment></comment></comment><comment><USER8> There seems to be quite an IKEA hacking community.

For anyone who has managed to miss it until now, the classic LACK Rack: [https://wiki.eth0.nl/index.php/LackRack](https://wiki.eth0.nl/index.php/LackRack)

<comment><USER9> What a coincidence that the space between the table legs exactly match that of a server rack.

<comment><USER8> I wonder if IKEA designs the stuff to 50 cm and it just happens to be in tolerance to 19 inches (48.3cm)

</comment></comment></comment><comment><USER10> Site slow for me, here is an imgur mirror [http://imgur.com/a/J2957](http://imgur.com/a/J2957)

<comment><USER11> Going on 7.5 minutes and still not downloaded. In 2016? He would be wise to compress his images. Can't wait until it's done so I can look at the Network trace in DevTools and see what is going on ;)

<comment><USER12> top notch perf shaming right there

<comment><USER11> Maybe said with a bit of snark, but I mean well! What I should have said was, "If the images were compressed, he'd save 14 meg and the page would load quickly." I work in performance so much I lose sight when I'm being an ass, sorry. :)

<comment><USER13> Thank you for being great and apologizing!

</comment></comment></comment></comment></comment><comment><USER14> Don't leave those ikea bags out in the sun, they fall apart rather...quickly....

<comment><USER15> I came here to say this... Those FRAKTA bags ([http://www.ikea.com/us/en/catalog/products/17228340/](http://www.ikea.com/us/en/catalog/products/17228340/)) are 100% polypropylene (thin strands, even). Polypropylene breaks down under ultraviolet light. The fact that the weave of the cloth is made from fine strands of polypropylene means that it will break down _very_ quickly in the sun.

There's a "fix" though that should be good enough for a camping trip or two! Coat the bag with a powerful sunscreen. I'm not talking about those "SPF 50" spray bottles--those will wear off pretty fast. No, use Butt Paste:

[http://www.buttpaste.com/](http://www.buttpaste.com/)

Yes, it's diaper rash cream but it's 16% _zinc oxide_ which is the primary ingredient in many sunscreen lotions/sprays. Even better, because it's a _thick_ cream it will _actually stick_ to that slippery blue Ikea polypropylene fabric and do a decent job at protecting it from the sun.

<comment><USER16> Making a cheap bag into a greasy, sticky cheap bag doesn't seem like a net gain.

<comment><USER17> Cheap? You can buy one from this guy for only $230 (!)

<comment><USER18> I found that very high at first, but then realized it's probably a pretty fair valuation of his time.

In the sense that you'd be silly to pay that price for that bag, but he'd be silly to sell it to you for any less if it takes him 10 hours to make it.

</comment></comment></comment></comment></comment><comment><USER19> It's probably more interesting that it is self made than it is interesting that it is made out of IKEA bags.

I find making it from the bags an odd choice, fabric with particular chosen qualities would probably be $10-$20 a yard.

<comment><USER20> Cordura, which is what most robust backpacks are made of, is surprisingly expensive.

<comment><USER21> Tyvek would probably make more sense for a project like this. $30 will get you 10 yards on Amazon

<comment><USER22> Tyvek is _loud_. I used it to sew furniture covers for a cabin that is left unoccupied in winter. Shaking out the bed covers to put them on is deafening. Walking with a Tyvek pack might drive you mad.

<comment><USER23> Those IKEA bags are pretty freakin loud too. Both are materials I wouldn't want near me.

</comment></comment></comment></comment></comment><comment><USER24> Some 20 years ago a homeless friend showed me how to make a backpack out of the fabric of a discarded umbrella.

I wasn't going to rummage through bins for broken brollies, so I bought a new one to break up, which he found immensely amusing.

I wouldn't recommend it, it worked but only if your standards are low enough.

</comment><comment><USER25> If any backpackers are intrigued by the idea but not keen on spending hours and hours hand stitching something, Ikea bags work great as waterproof pack covers if you don't have an actual pack cover. We used them on a two week trek around Patagonia with great results.

</comment><comment><USER26> You can get a 6x5 ripstop nylon tarp for free with purchases at harbor freight. Cut your patterns from that rather than a bunch of Ikea bags.

<comment><USER27> I was thinking that too after I saw the material the original bags were made from. It almost looks like IKEA has been shopping at HF too.

</comment></comment><comment><USER28> Awesome job. Here's an idea for v2: keep the IKEA bag intact and find a way to wrap/fold it in such manner that you are able to _mount_ it on some sort of shoulders/waist strap. You then use the same bag handles to hold/transfer the weight to the shoulders/waist. This assembly seems easier and the bag can still be used as such. Bonus: if the bag breaks you can replace it and have a new backpack for $1 :)

<comment><USER29> I'm thinking around messenger bags from Morrison's plastic/cloth shopping bags. Just need to work out how to stitch the stuff without a machine (sailing type needles or something and really strong cotton) and what to use for a strap.

Nice.

</comment></comment><comment><USER30> Looking at other stuff on this guy's website, he seems to be one of the most creative persons I've ever heard of. Amazing stuff there.

<comment><USER6> Now if only I could get a job in a similar line of work haha. Thanks

</comment></comment><comment><USER31> I'd like to ask a related question I've been meaning to get to doing some research on for a while but have been a little stumped on where to start with. Thought I'd borrow this thread to get the chance to ask HN.

Public transport in my area is really awesome so it's how I get about the most, and I occasionally carry a couple of reasonably heavy items (20kg+ / 44lb+) on short trips. I'm currently using a medium-size Macpac bag for almost everything, but it has no spinal support and I tend to hunch when it's full, and on the occasions all my items go beyond 10kg I have to split everything into an extra bag.

I'm currently wondering if there are unicorn backpacks out there that are reasonably light (not ultralight), reinforced to handle 20kg+ loads, and built to last for years.

I know the military use industrial carrying frames to handle their crazy 50kg+ (110lb+) loads, and I think I'm looking for something similar to that, since that's a situation where you _have_ to provide good support or you risk serious spinal damage, and the thing _has_ to last for a while while it's out in the field where it can't be easily replaced. That said, I don't want to be stick out like a sore thumb carrying a massive camo-fabric sack around.

</comment><comment><USER32> Site slow here.

[http://web.archive.org/web/20161122133120/http://sandiegomit...](http://web.archive.org/web/20161122133120/http://sandiegomitch.com/backpacking.html)

[http://webcache.googleusercontent.com/search?sclient=psy- ab&...](http://webcache.googleusercontent.com/search?sclient=psy- ab&site=&source=hp&q=cache%3Ahttp%3A%2F%2Fsandiegomitch.com%2Fbackpacking.html&oq=cache%3Ahttp%3A%2F%2Fsandiegomitch.com%2Fbackpacking.html&gs_l=hp.3..0i131k1j0l3.955.14647.0.15060.15.11.4.0.0.0.187.836.7j2.9.0....2...1c.1j2.64.psy- ab..2.13.822...0i10k1.Q75Ov3PJF_M&pbx=1)

</comment><comment><USER33> isn't the ikea bag same material as those blue tarps? Why not just use those plastic tarps which are already in tailor-friendly parallelograms

<comment><USER34> I can't be sure without touching both at the same time, but my memory of each says that the tarps are a lot thicker and heavier.

</comment></comment><comment> blubb-fish that's pretty cool. reminds me of me wanting to learn sewing, stitching and that stuff. knowing how to do that allows to alter suboptimally fitting clothes or repairing them. not to mention ... what this text is about ... designing yo I'mur own clothes, bags etc!

<comment><USER35> More generally, skills that make you good at reliably sticking things to other things are very useful. When you have mastered tape, glue, nails and screws, sewing is definitely a good next step.

</comment></comment><comment><USER36> I'm so impressed by this guy, it's well done and the initial problematic very interesting. It would be awesome if you could made a real website for it (and training your web-skills as you mentioned you are wishing)!

</comment><comment><USER37> This is pretty awesome looking!

</comment><comment><USER38> Honestly I'd buy this from you depending on the price. I don't want to make one myself, but I love the idea of a lightweight pack and (personally) don't mind the look. Actually quite like it. :)

Nice work.

</comment><comment><USER39> Seems like something that would make you suuuupersweaty on the back

</comment><comment><USER40> Is that Pacific Beach drive? I use to live right down the street from where that pic with frankenstein was taken, over on Riviera Drive.

<comment><USER6> Yep!

</comment></comment><comment><USER41> "Roughly 25 hours of work" wow!

still, the bag looks pretty great. nice job!

</comment><comment><USER3> Interesting as a DIY project, but I would strongly advise not using this for anything where functionality matters (camping, hiking, travel, etc). For just going to work/school it is a great fashion statement, but there are serious concerns

1\. no chest strap to help distribute the load. I see a waist strap which is nice, but chest is generally the bare minimum

2\. Those seals (stiches) aren't waterproof

3\. It is only as durable as the stitching

4\. The reason you pay for a "real" bag is for durability. That doesn't look like it would survive narrow trails that well. I am also sceptical as to how it would hold up on flights where you are forced to gate check all your luggage.

And before someone cites the ikea rope bag: Rope bags are generally what you use when you are climbing an hour or two away from the car/camp, at most, over fairly simple terrain. Farther or more strenuous than that and you are going to want a better more hands-free way of carrying that in addition to your gear.

Like I said, this backpack is cool and a nice fashion statement. But don't rely on it.

And if cost is the issue: Keep an eye out for sites like ebags. Can usually find great discounts and coupons throughout the year to get a solid Osprey (or whatever brand you prefer. I like Osprey) for on the order of 100 bucks. And while that is expensive (it actually isn't), understand that it should be lasting you at least 2-3 years, if not more.

<comment><USER42> For anyone interested in a serious DIY ultralight backpack, I'd suggest taking a look at Ray Jardine's "Ray-Way Backpack Kit". Jardine was a pivotal figure in the modern ultralight backpacking movement; his designs have been used successfully by countless AT and PCT through-hikers.

[http://www.rayjardine.com/ray-way/Backpack- Kit/index.htm](http://www.rayjardine.com/ray-way/Backpack-Kit/index.htm)

<comment><USER20> Do all those backpacks have umbrellas on them? Do people hike with umbrellas? Why does every single bag have them? Are they part of some kind of system for something specific?

<comment><USER43> Indeed - I've hiked almost 3k miles carrying an umbrella. Worn rain gear is a compromise between breathability and waterproofness - even if you keep the rain out, you'll sweat and it's trapped inside. Umbrellas keep rain off you, are very breathable, and double as sun protection when it's really hot. Only downside is when it's windy and rainy, so it's nice to have a poncho too.

</comment></comment></comment></comment><comment><USER44> REI has good ultralight backpacks for like $50 on sale.

<comment><USER45> when places like REI use the term ultralight, it means an entirely different thing than how an experienced backpacker thinks of the word. To an experienced backpacker, rei (or any chain) does not carry ultralight gear. There is an entire market of specialty gear makers making true ultralight gear and none of it is in retail brick and mortar.

<comment><USER46> I use this as an ultralight pack: [https://www.rei.com/product/892074/rei- flash-18-pack](https://www.rei.com/product/892074/rei-flash-18-pack)

<comment><USER45> Too small for backpacking, unless you are one of those bivy sack people with a matching $500 ul sleeping bag.

<comment><USER46> Yes I agree, sorry I thought people were just talking about a light pack. By that measurement, the Ikea bag is in a similar situation. It doesn't look much larger, maybe 22L?

<comment><USER45> I think its more like 30; look at the picture with the full stuff sacks. those are at least 7L stuff sacks, there are two of them, and theres room for 2 more of the same size. I backpack with a 32 liter and the interior volume looks comparable.

</comment></comment></comment></comment></comment></comment><comment><USER47> Yellow IKEA Backpack would be more valuable and unusual :) OK. Very interesting.

<comment><USER48> That would imply stealing those yellow 'only-for-in-store-use' bags.

</comment></comment><comment><USER49> I feel that the article ignores erginomics.

</comment><comment><USER50> I don't know what to feel about this. It looks janky as heck.

</comment><comment><USER51> Other than the satisfaction from the DIY process, this is a massive waste of time (and thus, money). Instead you can get something waterproof and ultra light.

<comment><USER52> That's a rucksack cover, not a rucksack.

<comment><USER53> It appears to be the correct order of magnitude for a cheap backpack: [https://www.amazon.com/Mozone-Lightweight-Resistant- Backpack...](https://www.amazon.com/Mozone-Lightweight-Resistant-Backpack- foldable/dp/B00XCNO83M/ref=pd_sbs_468_6?_encoding=UTF8&psc=1&refRID=K6A8KVMQ4S6NT6FBE2NA)</comment></comment></comment>


You Can't Turn the Network Invisible - <AUTHOR> https://www.pandastrike.com/posts/20160622-falcor-relay-leaky-abstractions-fallacies-of-distributed-computing <comment><AUTHOR> At the beginning of his presentation, Jafar Husain explained how a team at Netflix started out with a mostly RESTful API, but then it degraded to RPC. That suggests to me that REST really wasn't the best fit for their requirements. It's easy for us to say from the sidelines that they should have just tried harder to stay pure and follow the REST way. But requirements change, and the REST architectural style wasn't designed for today's world, where users don't want to think about the distinction between their devices and the network. I think it's quite likely that Relay and Falcor, having been designed by teams working on large-scale consumer applications, really do make some progress toward solving some problems these teams face better than REST does.

More generally, I'm skeptical of any hard-line position which insists that you just have to stay pure and follow the true way. I already rejected one religion; I don't want to get sucked into another.

<comment><USER2> We're not religious about REST. For example, see:

[https://www.pandastrike.com/posts/20151215-http-rest- great-b...](https://www.pandastrike.com/posts/20151215-http-rest-great-better- developer-experience)

and

[https://www.pandastrike.com/posts/20160210-rest-is-the- wrong...](https://www.pandastrike.com/posts/20160210-rest-is-the-wrong-way-to- understand-http)

We've also tried to be specific in how you might approach addressing the limitations of HTTP in a way more consistent with the design of the protocol:

[https://www.pandastrike.com/posts/20151022-rest-data- api](https://www.pandastrike.com/posts/20151022-rest-data-api)

and

[https://www.pandastrike.com/posts/20160509-http-is-the- new-l...](https://www.pandastrike.com/posts/20160509-http-is-the-new-lisp)

In fact, our thesis in this article is not about REST at all, but the design goals of projects like Falcor, which may be unrealistic. And it's those unrealistic expectations of what's possible are why people are turning from HTTP.

<comment><AUTHOR> OK, I was wrong to accuse you of being religious about REST. Thanks for the links.

<comment><USER2> :)</comment></comment></comment></comment>


Why noobs don't make money online - A blog with real info about Adsense and SEO - <AUTHOR> http://makemoneyforbeginners.blogspot.com/2009/02/why-noobs-dont-make-money-online.html

<comment><USER2> Thanks for the nod.</comment>


The Thousand Brains Theory: Framework for Building Intelligent Machines [video] - <AUTHOR> https://www.youtube.com/watch?v=5LFo36g4Lug <comment><USER2> Related HN conversation on a podcast interview with Jeff Hawkins - [https://news.ycombinator.com/item?id=20326396](https://news.ycombinator.com/item?id=20326396)</comment>