Ask HN: Source of income generating stuff you can suggest to integrate to App? - <AUTHOR>

I am new into mobile development and would like to ask for experts here what are best source of generating income for a mobile app. For one, we can make it a paid app - but i don't want to make it a paid app (for now at least). Just want to ask you guys if you can suggest something. Thank you. <comment><USER2> Disclaimer: I am not in any way an expert.

Your main options (besides moving to the paid app model) are in app purchases and advertisements:

In app purchases pros:

 _No advertisements clogging up your screen, meaning improved user experience and interface._

 _Infinitely scaleable to your imagination, just look at Zynga, whereas advertisements are limited within the context of an app._

 _If your app is addictive these can be very lucrative._

In app purchases cons:

 _Requires much extra content creation, or limiting or the initial app._

 _Most users don't use them, meaning the majority of your user base will be losing you money._

 _Can come across as cheap and that your paying users are just "buying" their success, especially if it takes off._

Advertisement pros:

 _Much more distributed income generation, you aren't relying on a select few purchasers._

 _A spike in traffic will generally directly correlate to a spike in income, not always true with in app purchases._

 _Much less difficult to manage once it has been set up, very much a fire and forget weapon._

Advertisement cons:

 _Most users become annoyed by pop up windows and adverts taking up half their screen._ \- This is a biggy.

 _The ad agency takes the lions share of the profits, so you could potentially by capping your income to a certain amount when in app purchases could be more lucrative._

<comment><AUTHOR> thanks, your insights are appreciated.. hmm, I'm thinking now to moving it to a paid one.

I'm not sure if an approach like this is okay: free version - no need to pay, but only can enjoy limited stuffs paid version - enjoy everything

<comment><USER2> If you're a capable developer, and by this I mean not just coding but being able to push out an addictive, enjoyable application, why not release the full app for free, then ask for payments for an expansion, essentially an in app purchase adding 3 times the levels, or whatever.

If they are already hooked the gamble could pay off.</comment></comment></comment>


Ask HN: What license should I use? - <AUTHOR> I am writing a software and want to keep it open source. I also want to earn to live of it, through maintain that software. I currently licensed it under GNU GPL v3, but got a couple of requests that it doesn't allow making profitable propriety software on top of my work.<p>It is a server-side software which people are required to host themselves. <comment><USER2> There is a few standard ways to earn a living on writing open source software, all with benefits and drawbacks.

1: Selling exception. Keep it GPLv3 (or AGPLv3) and offer profitable propriety software to pay you for an exception. The major drawback is that you can't use others gpl'ed software in your software, including patches.

2: Subscription based donation like patreon. It is more stable form of donation if you got a existing user base that is willing to upfront commit to it. License choice is generally best as a community decision.

3: Hosting provider. In this case you want to corner the market in hosting the server-side. If people are required to host themselves than this is obvious a non-option. AGPLv3 is generally a good choice in keeping competition at bay and honest.

<comment><AUTHOR> Thanks for the nice overview. Option #2 seems like the way I would want go.

</comment></comment><comment><USER3> Why not MIT?

It seems like an universal answer to "licenses are too complicated, just do whatever you want with it" scenario.

<comment><AUTHOR> How would I be able to earn off it ? I considered the option of "donate something button", but I haven't seen any projects where the developers were able to live comfortably on the donations. Plus donations isn't stable.

Hoping to find balance somewhere.</comment></comment>


Probability Theory for Physically Based Rendering - <AUTHOR> https://jacco.ompf2.com/2019/12/11/probability-theory-for-physically-based-rendering/ <comment><USER2> That's nice to see this on hn. Some might recall a website called flipcode, the author used to write articles there under his handle "phantom". Ompf is a community for raytracing enthusiasts, where real time raytracing was pioneered way before the adoption by e.g. gpu manufacturers.

<comment><USER3> Wow, I do remember flipcode (and phantom). Strange to see those names after so many years. It was from a different era of the web when it was full of niche, useful sites like these populated by domain experts. I miss those days :(

<comment><USER4> Twitter is a good source of information now, and it in fact looks like the free tutorial is making a comeback with Twitter as a podium. \- J. Bikker aka Phantom. :)

</comment></comment></comment><comment><USER5> Probability of a hacker news top 10 breaking your hosting: high

[https://web.archive.org/web/20191213142747/https://jacco.omp...](https://web.archive.org/web/20191213142747/https://jacco.ompf2.com/2019/12/11/probability- theory-for-physically-based-rendering/)

<comment><USER6> Interesting though, I don't think I've ever seen a code 507 in the wild!

<comment><USER7> Does it mean that the logs got so big that the httpd wouldn't serve requests, for want of space to store the record?

<comment><USER6> I don't know actually. 507 was introduced in rfc 4918 alongside WebDAV, so my naive assumption is that its main use case was for something more associated with authoring or general file manipulation.

I'm surprised that it has much use for a normal GET request, but I guess anything can be a bottleneck!

</comment></comment></comment></comment><comment><USER8> I vaguely remember a good probability mathematician talking about an optimization as possible with sorting what objects to render and it being much more efficient during my time in IT in the university. Ie with math you could exclude a lot of the objects to render. Happy to see it implemented and looking forward to game with it!

</comment><comment><USER9> I only glanced through the article and wonder if it would be easier to use deterministic grid or adaptive grid?

<comment><USER10> ...you should probably read the article since it covers that.

<comment><USER9> Ok, I read the article. I guess this is more educational exploration rather than practical advice. So conclusion is that deterministic grid or adaptive deterministic grid (not directly discussed) beats random sampling.</comment></comment></comment>


Quantopian wants to Turn Stock Trading Algorithmic - <AUTHOR> http://www.forbes.com/sites/petercohan/2013/07/01/quantopian-wants-to-turn-stock-trading-algorithmic/ <comment><USER2> I'm going to say a couple of things about algorithmic trading and the knee jerk reactionaries.

First--there is an industry that makes pretty good money from practicing algorithmic trading. I work with some of them. Some of them do well. However, on the average, returns in that business are subpar. Then again, on the average, most people are idiots. On the average, most startups fail. "On the average" is usually not taken as a reason to not do something by this community (HN), at least allegedly.

Second--there are _plenty_ of reasonable issues to raise whenever this comes up. For instance--your average investor is going to have a tough time of this --for starters due to transaction costs, taxes, etc. Then again, your average investor is going to have a tough time of the stock market in general. Again, the average, by definition, is not impressive and can never do any better than --well--average. But we don't want to be in the average. That's the whole point of much of what we do here. Except when it comes to exploiting financial markets, in which case the average is all that matters?

Point being--is it possible to have a reasonable discussion about statistical analysis of _markets_ and what, if anything, might be done to exploit any regularities found? Is it really so difficult to believe that regularities in relative price movements exist? And yeah, I get it--there's something generally slimy about the whole industry, and there have been plenty of hucksters over the years (and in the present). Then again... isn't this true for the entire tech industry, more or less?

So, you don't have to take part in it, you don't have to learn about it, but can we PLEASE have a better response than "oh, backtesting, that doesn't work, dur"? I mean, yes, there's a fair amount of "lead into gold" type stuff there --but I really don't think it's an unbelievable stretch of the mind to say that regularities exist in markets. No doubt those regularities change, but wouldn't it be interesting to see how quickly and why? And maybe some people can be better at it than others (that doesn't happen anywhere else right?)

So yeah, don't get too excited, but then again, don't be so damned pessimistic. Markets are a system like any other, probably some of the most interesting systems around because they are so hard (some say _impossible_ ) to grasp.

<comment><USER3> I dunno about average algorithmic traders being idiots. I think people have to have a certain level of smartness to even grasp what algorithmic trading is, let along attempt it. If the average return is subpar, then that's out of the people that are smart enough to be in the business, grasp the concept, and try it enough to qualify for whoever's doing the measuring.

<comment><USER4> Signal to noise ratio is very high,50x in some cases which makes this a very hard (though interesting ) problem.

</comment></comment></comment><comment><USER5> A better title would be 'Quantopian wants to turn stock trading algorithmic for everyday investors'. These techniques are used by quants already (as the article states).

<comment><USER6> Well it's a great way for the average investor to get destroyed by transaction fees.

<comment><USER7> Why would, say, a VWAP order cause more fees than the equivalent limit orders?

<comment><USER8> I guess his understanding is that trading algorithmically means trading a lot (it doesn't); at low volumes transaction costs dominate.

</comment></comment></comment></comment><comment><USER9> "Backtest your algorithm, for free, against our 11-year history"

Hahahaha, yeah, I don't think so. If you guys are really interested in this sort of thing, the MOST important thing is to have a comprehensive database free of biases and errors. For example, survivorship bias is a huge deal, and I wouldn't trust any platform that isn't serious enough to have a historical dataset that is longer than 11 years long to be free of these kinds of things.

<comment><USER10> [https://www.quantopian.com/faq](https://www.quantopian.com/faq)

> The data includes all companies that were traded, including companies that > have subsequently gone out of business. This is very important in order to > avoid survivor bias. Without this complete data set, your algorithms would > be be blind to the possibility of bankruptcy and the resulting losses.

<comment><USER9> Good to see at least that. Personally, 11 years is not enough time to see enough things to Black Monday or the tech crash. Hell, it's not enough time to see a REAL bear monster bear market. Also, what else is included in the database? So far, it just seems that prices are the only thing included. I looked through their documentation, and I can't find things like valuations and accounting data.

<comment><USER11> I understand that the limited amount of data can make for some easy false positives on trading algorithms, but how relevant do you really think market movements from over 11 years ago really apply to today?

<comment><USER12> I hear a lot of people talk about needing more than 10yr of data for backtesting, and this is something that is often overlooked. The driving forces behind market data are unobserved and extremely complex, so you simply can't control for all the variables. If you can control for at least _most_ of them, then you are in a situation where more data is NOT always better.

The one elephant that jumps to mind is liquidity. The mechanisms by which liquidity in the markets affect the end results are absolutely key to how your algorithm's interactions with the data will pan out. With that in mind, the methods by which we come by liquidity have _dramatically_ transformed over the years, and market makers from >10 years ago operated in an entirely different way. That's my $0.02, anyhow.

Anecdotal evidence: I have first-hard experience implementing algorithms that chugged along just fine with 10 years of data for backtesting.

<comment><USER13> Exactly. After Reg NMS and other massive regulatory changes, it's an open question as to whether the post-2007 market system is the same as it was before.

You could ask the same question about many different regulatory changes, but Reg NMS is likely to be the biggest.

</comment></comment></comment></comment></comment></comment><comment><USER14> Honestly the only type of algorithmic trading I would trust is algorithmic trading based at least partially on fundamental data, of which Quantopian has none.

Good luck to all you momentum/technical types though, I'll be sitting in the corner reading 10k's.

<comment><USER12> I'm not aware of any quantopian algorithms that make use of fundamentals, but that doesn't mean they aren't there. There are lots of fundamentals that are available as processed variables (P/E ratios, etc.) which can be used as an indicators of financial health. Now, certainly that doesn't replace roping off an afternoon and diving into the last 5 years of 10K's to get a real understanding of what's happening with that company, but it doesn't mean that algorithmic trading can't include fundamentals. Indeed, considerable effort has been expended trying to intelligently scrape+process 10K's, which are all available from the SEC, in an (semi-)automated way.

Also, as a point aside from the one above, in the ideal world markets would be driven entirely by the real value underlying the securities being traded. But that's not the case. Markets are highly influenced by news, to give one example. So to say that only the fundamentals can be trusted is a little bit narrow minded (in the pure sense of the phrase, not meant as a shot at you). I think that particularly as the time horizons of your positions get longer, it becomes more and more critical to include fundamental data in your analysis.

<comment><USER14> I never said algorithmic trading can't include fundamentals, quite the opposite, I just said that until Quantopian includes fundamental data, it's not all that interesting to me. P/E barely scratches the surface, I'm talking about all the data revealed in standard financial statements. If I were ever to trust my money to a security selection algorithm, it would have to analyze more than just price movements.

</comment></comment></comment><comment><USER15> So, is this an effort by more sophisticated players to plant the seeds for a new market to reap? You know, since algorithmic trading is starting to dwindle as a cash cow.

<comment><USER16> I think you may be mistaken. High-frequency trading is becoming less profitable as an industry, but algorithmic trading in general is most definitely not.

<comment><USER15> Really? As I understand it the world is quickly becoming saturated and major players are starting to take their chips and leave the table. The risk is quickly catching up to the reward and consolidation into a type of commodity equilibrium is inevitable.

What areas of algorithmic trading are escaping the Great Chill?

<comment><USER14> "Algorithmic trading" is just a broad umbrella that encompasses any trading system where a computer algorithm is making the trades based upon pre-defined rules. Buying the S&P every Tuesday can be considered "algorithmic trading."

And of course, the answer to your question about which algorithms are working, they are the ones on the opposite side of the trades of the ones that are losing. (Or, alternatively, the ones you can't read about in academic papers or books.)

<comment><USER15> I am not talking about 'warehouse picking order' style algorithmic trades that are designed to make transactions cheaper or more automated merely for convenience.

Equilibrium is coming.

But that is Ok. Quants can go into material science and model new and useful materials by studying their higher dimensional black hole equivalents [1].

[1] [https://www.simonsfoundation.org/features/science- news/signs...](https://www.simonsfoundation.org/features/science-news/signs- of-a-stranger-deeper-side-to-natures-building-blocks/)

<comment><USER17> > _Equilibrium is coming._

So yields, returns, and inflation are finally stabilizing as the market matures and approaches its "true value"? Nope, because equilibrium is a concept which works well in the natural sciences, but quite erroneous as applied in economics. This is George Soros's argument in his books about the Principle of Reflexivity, which differentiates social systems from natural ones.

What _is_ happening, is merely that trading volume/volatility has tapered off since the '08 crisis. That's expected; empirically, volatility continues to be clustered and autoregressive (a self-exciting process). Its a cycle that will pick up again (one can expect), eventually.

<comment><USER15> But I am not talking about the level of social systems. Of course the market itself is not approaching equilibrium. But the liquidity enhancement market is. There will always be money to be made there but not the bonanza that's existed up to about two years ago.

<comment><USER17> But that's mostly due to the much lower volume and volatility (rather than more competition). When its low, so is the demand for liquidity provision. But that demand will come back with the next volatility cycle.

Actually, volatility is only clustered when measured in calendar time. Its much more constant when measured in event/transaction time (plot price against cumulative volume, rather than date/time).

</comment></comment></comment></comment></comment></comment></comment></comment><comment><USER18> A friend of mine is working on something remarkably similar at [http://QuantConnect.com](http://QuantConnect.com)

</comment><comment><USER19> Can't wait for Economics 2.0 to harvest the inner solar system.</comment>


The man who was caged in a zoo - <AUTHOR> http://www.theguardian.com/world/2015/jun/03/the-man-who-was-caged-in-a-zoo

<comment><USER2> Amerikkka, home of the brave, land of the free . . .</comment>


Ask HN: How to pitch when you're not solving a problem - <AUTHOR>

Hi, we have launched a startup couple of months ago with a seed round and given the traction we have we are now raising our series A. Most the pitch deck I've seen involve a slide "problem you're solving". Our startup doesn't really solve a problem, it just helps people do what they used to in a fun way.
How would you pitch something that doesn't solve a real problem but improve what's existing? <comment><USER2> It sounds like the problem you're solving is "people like to be amused."</comment>


Lyft Files to Raise as Much as $1B - <AUTHOR> http://techcrunch.com/2015/12/21/lyft-files-to-raise-as-much-as-1-billion/ <comment><USER2> >Amid reports of Lyft's financial struggles in its recently leaked financials, it's obvious why the company seeks to raise so much money — the on-demand transportation market is a tough place to operate, especially with competition like Uber. According to Bloomberg, the ridesharing startup took a net loss of $127 million in the first half of this year while bringing in less than $47 million in revenue.

Does anybody know how this loss compares to Uber? I don't recall any of their financials being leaked recently.

<comment><USER3> Uber loses at least $470M / year, if not more (unsure if the number is per quarter, half-year, or full year) [1].

Lyft's struggles have nothing to do with their losses, and all to do with the fact that they're losing the market to Uber.

[1] [http://www.businessinsider.com/uber-reportedly-operating- at-...](http://www.businessinsider.com/uber-reportedly-operating- at-a-470-million-loss-2015-6)

<comment><USER4> Uber _lost_ 470m/period. As the article mentions, these figures are outdated by a number of years and completely irrelevant - Uber is hitting more than 2.5 billion in revenue (commission) this year.

According to public information, Lyft is losing approximately 3 to 5 times the amount of money _per ride_.

<comment><USER3> If those numbers are indeed out of date (I'm not taking an Uber spokesperson's word for it), I would be inclined to believe they are losing _even more_ than $470M/period, given their extremely aggressive expansion and extremely aggressive fundraising.

<comment><USER4> In China, yes, but recent Uber aggression has been anything but aggressive. Just look at driver referral incentives been slashed from $750 to $200 (if you're lucky).

</comment></comment></comment></comment></comment><comment><USER5> Taxi fare is something everyone wants to save on. Once Uber and Lyft start making big margin on their service other low key and smaller companies can compete with them. Pretty much like airfare. Price is the king and low cost companies are doing a lot of business. I'm not sure how this Uber/Lyft story will end but I'm pretty sure it's not going to end like Facebook or Google.

<comment><USER6> Unless one brings robot taxis. Lowest price and highest profits.

Right now it's just an app for taxis. But robots totally flip the market on head.

<comment><USER7> I don't see how this will fly even with robot taxis. Not for too long at least. I think self driving cars will be commoditized easily. Any new player can simply leverage the technology. The economy of scale is simply not there in this business, compared to the leverage Google and Facebook have. There is hardly any network effect, and it is still highly capital intensive even with robot cars. So while they may succeed in being and maintaining their status as multi-billion dollar companies, I am not seeing how they can go much further in the long run.

<comment><USER8> Completely disagree regarding the network effect of Uber vs. Lyft. The system is highly network dependent. Most Uber drivers would prefer to drive for Lyft because Lyft pays more (partially why they're losing more money than Uber), but in most markets Lyft doesn't have as many riders that use the service. As a driver, you want to maximize time spent with a fare vs. fare-hunting. Similarly, as a rider, you are weighing price vs. time meaning most people will pay more $ to wait less for their ride.

Most drivers I talk to drive for both and keep both on, but get more pings on Uber than on Lyft. In SF Lyft has more mind-share and it's a more even split.

FWIW I've lived in both SF and NYC since the rise of these services.

<comment><USER7> But that type of network effect is easily undermined by a service that offers cheaper fares. I saw this happen first-hand in India where Ola cabs, which was being used by almost everyone, quickly started losing users to Uber once Uber started their massive discounts and promotion series in India.

</comment></comment></comment></comment></comment><comment><USER9> How big is the gap between Lyft and Uber in India and China and other large Asian markets? In China, is there a state-favored rival [1] that could just shut out both? From an American perspective, it's hard to imagine Lyft overcoming Uber's lead...but maybe it's a sensible investment if Lyft has a strong chance of being bought by an Asian company?

[1] edit: Found this Fortune article, which describes Didi-Kuaidi as the "Uber of China" with 1 million drivers versus Uber's 100,000 drivers. Also, Didi is an investor in Lyft: [http://fortune.com/2015/09/30/will-china-be-ubers- waterloo/](http://fortune.com/2015/09/30/will-china-be-ubers-waterloo/)

<comment><USER10> Uber has very little chance to win China market considering competition from Didi which is backed by Tencent and Alibaba. Considering the insurmountable dominance of Tencent's Wechat and Alibaba's AliPay on mobile phones in Chinese market.

Some reports that Didi has 80+% market in China and Uber gets 10+%.

<comment><USER11> Baidu was a strategic investor in Uber, and they lead another $1.2B round a couple of months ago. Both companies have local giants backing them, so anything can happen. If I had to bet, though, I'd bet on Uber winning in China if they can win enough of the rest of the world.

[http://techcrunch.com/2015/09/07/uber-confirms-its- raised-1-...](http://techcrunch.com/2015/09/07/uber-confirms-its- raised-1-2b-more-in-china-led-by-baidu-as-rival-didi-kuaidi-gets-3b/)

<comment><USER10> I know this but BIDU is leaving first tier internet companies in China. This can be seen from its market cap which is almost a third of alibaba or tencent.

No matter what you bet -- you should always bet on something you can control not others.

</comment></comment></comment></comment><comment><USER12> If they actually manage to raise this amount of money then an amazing amount of capital is going to be destroyed over the next couple of years. Uber and Lyft going head to head to try and grab a monopoly is an extremely effective way for investors to lose a truck load of money.

<comment><USER13> "Destroyed" is an unfortunate term to use. The drivers and riders will benefit who are predominantly not rich, so its actually a kind of stimulus.

<comment><USER14> Maybe not rich but a lot of the lower income people in my neighborhood in Brooklyn aren't using Uber or Lyft regardless of how cheap because they don't have much money period. You have to have a phone and internet access for these services so it's definitely not hitting the lowest brackets.

<comment><USER15> Do you have data to support this? I too live in Brooklyn and have found the opposite to be true.

<comment><USER16> Brooklyn is a big place, and the person you're replying to did just say his neighborhood… probably little data available on any scale let alone the scale of one's neighborhood, aside from anecdotal.

</comment></comment></comment></comment></comment><comment><USER17> Well I guess that could explain the 50% off rides promo they've been running in NYC for the past 6 weeks. Seems like every Sunday I get a push notification that it is extended.

<comment><USER18> I wish Apple would actually ban APNS spammers. Yelp does it too ("Yelp Weekly" or something).

<comment><USER19> Settings -> Notifications -> off?

<comment><USER18> No, that's not an acceptable solution. Spammers should be banned. But I actually wasn't strong enough:

[https://developer.apple.com/app- store/review/guidelines/#pus...](https://developer.apple.com/app- store/review/guidelines/#push-notifications)

By section 5.6, Lyft should be removed from the App Store. I wish they'd do it!

</comment></comment></comment></comment><comment><USER20> As an adult I don't want to get into a car with a huge pink mustache on it.

Get over myself? Sure, but the brand is terrible.

<comment><USER21> They've backed away heavily from the mustache.

<comment><USER22> Its a magnet now, but there's still a mustache on the car and it still looks stupid as hell.</comment></comment></comment>


How the pilots of Lion Air Flight 610 lost control - <AUTHOR> https://www.nytimes.com/interactive/2018/12/26/world/asia/lion-air-crash-12-minutes.html <comment><USER4> There have been a surprising number of air disasters in recent years caused primarily by air data sensors returning false data.

\- Birgenair Flight 301 - B757. Pitot tube clogged possibly by insect nest, false overspeed indication, autopilot commanded pitch-up, alarms, stall warning, crew confused about speed, loss of control. 189 dead.

\- Air France Flight 447 - Airbus A330. Well known. Pitot tube clogged by ice, confusion about airspeed, loss of control. 228 dead.

\- Saratov Flight 703 - An-198. Pitot tube frozen. Three airspeed indicators all disagreed. Loss of control. 71 dead.

\- Lion Air - Angle of attack vane failure, from parent article.

That information could be checked against GPS, and at least one aircraft does this. But that has its own problems.[1] Checking against an inertial system is another possibility. Those are complicated, though. The classic airspeed, altimeter, and angle of attack vane are so simple.

[1] [https://www.gpsworld.com/gps-disruption-a-full-fledged- aviat...](https://www.gpsworld.com/gps-disruption-a-full-fledged-aviation- problem/)

<comment><USER5> Do aircraft inertial measurement systems ever provide linear velocity information that isn't trash? I had assumed not (except for special cases where you can do e.g. a zero-velocity update)

An inertial measurement system cannot measure velocity. It's insensitive to which inertial frame it is in. (to move from a non moving frame to a moving frame, you must accelerate, which it could detect. but then you have to integrate these accelerations over time)

<comment><USER6> Your assertion is simply demonstrated to be untrue.

Inertial systems integrate all measured accelerations over time to compute present velocity and position. They are periodically corrected with external references. The accuracy is limited to the accuracy of the accelerometers, the sampling frequency and the accuracy of the digital math, among other things.

This IMU idea could be used, but I am not aware of any current commercial IMUs in airliners - but I am not an airline pilot so that does not count for much.

If I were given conflicting information I would see how the plane is acting. I have flown planes with various primary instrument failures over my decades, some in actual instrument conditions, and always had sufficient secondary sources of data to determine the situation. As an example in a piston plane: Tachometer fails? Cross check fuel flow, manifold pressure and airspeed - subject to mixture control which can be reasonably set using "lean to roughness and enrich" method. Been there, done that. I have had an altimeter fail insidiously slowly, when water got into the static lines (despite redundant ports and properly routing them upward), while in actual near minimums in a non precision approach. (I used GPS altitude cross reference and odd seeming behavior of altimeter needle to diagnose and switch to alternate static.)

Importantly, if the plane is flying straight and level and sufficiently fast, over time this becomes a "feel" and you can tell if something is extraordinary. Maybe not on airliners, but definitely the piston planes I fly a lot and probably the small jets I fly on occasion.

This is why some of these things are mystifying to me. If your engines are set to a certain power and seem to be operating properly, and your attitude is just so, in the absence of unusual meteorological conditions your plane should be performing in a manner consistent to your last experience. If your stall warning is going off, well, maybe the instrument broke. Air France is really scary mystifying.

Look, I am a software engineer so I get it, people can get locked into a misconception about a fault and not step away long/far enough to consider other alternatives. It happens a lot in debugging. But for whatever reason my brain works much faster and more dynamically when shit happens in the left seat of an airplane having problems.

<comment><USER7> > But for whatever reason my brain works much faster and more dynamically when > shit happens in the left seat of an airplane having problems.

Maybe you didn't intend it but this sounds a lot like "couldn't happen to me!"

<comment><USER6> LOL. Oops.

I meant to mean "It has most definitely happened to me" although not yet in the context of piloting - but in other contexts.

</comment></comment></comment></comment></comment><comment><USER8> What the pilots experienced was indistinguishable from runaway stab trim, and shutting off the stab trim from the switches on the console is the correct response. There's a loud distinctive sound when the trim runs, and the wheels that bracket the console turn, so it's pretty obvious. The previous flight's pilots had indeed done this. The pilots are trained for this. They has 12 minutes to shut off the repeated action of the runaway stab trim.

Additionally, the airplane should have been grounded after the previous flight, as runaway stab trim is a serious problem, until the fault was found and corrected.

Equally badly, the flight crew was probably not informed of what had happened on the previous flight.

<comment><USER9> Well sort of but not quite. When the pilots clicked the trim up switch on the yoke, it disabled the MCAS system for 5 seconds -- i.e. it made the problem go away temporarily. Then MCAS comes right back with more nose down trim. This is not a typical runaway trim situation where it's just continuously rolling in more trim. The pilots had no idea that this system existed or that a "runaway trim" failure could have these characteristics.

Sure, it's easy to say from the ground with what we know now that all they had to do was flip a couple of switches, and that a previous crew managed to land safely. However, the job of an airplane is not to be safe only with quick thinking, above average pilots. If a single sensor failure can present a situation that 99% of pilots will successfully diagnose and recover from, you're looking at multiple crashes per year.

<comment><USER8> The pilots did not need to diagnose the system. It would have been obvious that the trim system was running, and was causing the nose down. The trim cutoff systems are right there on the center console. They dealt with the issue for 12 minutes, lightning reflexes were not necessary.

The NTSB will of course look into the CVR, the pilots' training, background and track record to try to figure out why they did not use the cutoff switches. I'm very curious about that.

Similar types of accidents have occurred in the past and turned out to be CRM (Cockpit Resource Management) issues, where the copilot recognized what was wrong but was intimidated by the pilot into doing nothing.

</comment></comment></comment><comment><USER10> What is never mentioned is that since forever runaway stabilizer is one of the FEW memory items.

Here it is. To be qualified as a pilot you have to have this memorized.

I. Runaway Stabilizer

CONTROL COLUMN - HOLD FIRMLY

AUTOPILOT (if engaged) - <USER2>

Do not re-engage the autopilot.

If the Runaway Continues

STAB TRIM CUTOUT SWITCHES (both) - <USER3>

All this drama around "fighting the controls" and "fighting the plane" is weird. This is not some procedure you need to lookup, this is one of a few memory items.

<comment><USER11> That process isn't sufficient on the 737Max. That is the point; to make it fly like a 737NG Boeing added an additional system, MCAS, that requires the AoA sensors to be manually disconnected during a malfunction or it will continue commanding elevator pitch. You could run through your memory drill as many times as you like, it wouldn't have helped in this case.

<comment><USER12> The FAA Airworthiness Directive (2018-23-51) can be found at the address below (pdf). There is no mention of manually disconnecting the AofA sensors. The addition to the Airplane Flight Manual required by the AD explicitly says "do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight."

While I don't think pilot training is the only issue, we can't assume a crash was the most probable outcome following from the failure of the AofA indicator in question.

[https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf...](https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/fe8237743be9b8968625835b004fc051/$FILE/2018-23-51.pdf)

</comment></comment></comment><comment><USER13> The page is graphics loaded page with floating paragraphs over a single "sheet of wallpaper" showing interior and exterior diagrams of the aircraft. I can see it not working worth a damn in any kind of Reader View.

FWIW, nothing new here, but it's a good 3rd grade overview for the layperson.

And I am a Boeing guy, through and through, but they screwed the pooch on this one. RIP, Lion Air 610.

/Acey

(me: FAA licensed dispatcher)

<comment><USER14> Can you point us to a better article?

<comment><USER15> Here's the actual safety board report, including flight data recorder graphs: [http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/pre/2018/20...](http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/pre/2018/2018%20-%20035%20-%20PK- LQP%20Preliminary%20Report.pdf)

Looks like there was a problem with the autopilot trim, likely due to a faulty sensor, and the pilot just needed to switch off the autopilot instead of fighting it — the previous flight of that aircraft experienced a similar issue, and they just turned the autopilot trim off and carried on normally. :(

The graphs on PDF page 23 are particularly morbid, and you'll note that two of the final auto nose-down commands are of longer duration than all the rest.

<comment><USER15> Ah, this is quite good as well: [https://leehamnews.com/2018/11/14/boeings- automatic-trim-for...](https://leehamnews.com/2018/11/14/boeings-automatic- trim-for-the-737-max-was-not-disclosed-to-the-pilots/)

Apparently it wasn't the standard autopilot trim, but a special safety program specific to the 737 MAX. Which still is just a switch to disable, if you know that switch is there, or that there is a checklist for dealing with runaway trim, or that you're aware that auto-trim commands are the reason your plane keeps nosing down...

<comment><USER16> I think the most important point described in that article is that the MCAS trim, unlike the other kinds of elevator trim, _isn 't_ defeated by limit switches on the yoke - and that this critical information was not in the training or flight manual.

<comment><USER17> If true, then this right here is the problem root. Why isn't pilot limit respected with regard for the MCAS specifically? Are any other systems so independent?

I remember years ago the Boeing folks claiming that the automated Airbuses would be dangerous because the pilot always knows best. So how did it come to this on a Boeing?

<comment><USER16> The answer appears to be something along the lines of _" because the whole point of MCAS is to stop the pilot flying the aircraft beyond the limits of stability"_.

</comment></comment></comment></comment></comment></comment></comment><comment><USER18> These human-machine interface failures always fascinate me. The NYT makes the quip about not being able to look down and note the trim, but speed doesn't need to be high to have these failures. It seems to be more related to system complexity misunderstandings or compounding interpretation issues. Look at the grounding of the Royal Majesty - not exactly some high speed object; it all amounted to a misunderstood icon. See: [https://ti.arc.nasa.gov/m/profile/adegani/Grounding%20of%20t...](https://ti.arc.nasa.gov/m/profile/adegani/Grounding%20of%20the%20Royal%20Majesty.pdf)

</comment><comment><USER19> You would think it would make sense to automatically disable the MCAS system and sound a warning if the aircraft detects conflicting readings from it's sensors.

<comment><USER20> Due to the way the engines are mounted on the frame, which enhances their efficiency, they also cause more of a "upward thrust vector." This makes it very easy for this plane to reach dangerously high AOA in certain scenarios, particularly during turns.

The MCAS has a specific and important function and just turning it off is probably not going to increase safety. The real problem was the Boeing did not disclose the existence of this device and it's functions in aircraft training, according to one source, because they did not want to inundate new pilots with too much information about the plane and it's attendant safety systems.

Perhaps, had the pilots known, they would have seen the stick shaker/stall warning system activating on _one side only_ as a serious indication of an Airspeed/AOA system fault and the potential for incorrect MCAS outputs being generated.

They might have known to disable the electronic trim control, bypassing the MCAS, and then to manually fly and trim the plane with the aforementioned thrust vectoring taken into consideration. They could have trained for this. That would have all given them the best safety margin for survival here.

<comment><USER9> In the case of a disagreement between the AoA sensors, the obviously correct thing to do is for the computer to disable MCAS and put up a warning light. The conditions MCAS addresses only happen when the AoA gets very high, such as in a slow speed over banked turn. The plane is stable in normal operation.

Think of how a human would react: One sensor says everything is normal. The other says a very rare emergency situation is occurring. Since the sensors disagree, you know one of them is defective and wrong. Applying a very rarely needed emergency correction when you know that you have a sensor fault is not reasonable.

Even applying the stick shaker is confusing to the pilots and dangerous. Much more appropriate is a warning light of a sensor malfunction/MCAS disabled. Then the pilots must simply be extra careful to not make overly banked turns for the remainder of the flight, and replace the sensor on landing.

<comment><USER20> > the obviously correct thing to do is for the computer to disable MCAS and > put up a warning light.

The only problem with that is that problems rarely happen isolation, and you have to consider whether the pilots are going to notice the warning in the midst of several others and if they are going to give it the appropriate priority and consideration while flying.

> Think of how a human would react

That's exactly it, though.. look at Air France 447. The system automatically disabled itself and put the plane into an "alternative law." All automatically. The pilots did _not_ notice this, and still flew the plane into the ocean even though they had several minutes to work the problem.

It's not that simple.

> Even applying the stick shaker is confusing to the pilots and dangerous.

All evidence to the contrary. The stick shaker is an amazing safety device because it demands priority of consideration. It's not going to get lost in the noise of a degrading cockpit. Seriously, go listen to some cockpit voice recorders of a disaster.. it's never what you would expect.

<comment><USER9> > problems rarely happen in isolation

Problems usually happen in isolation. Your dataset is skewed because you've read a bunch of accident reports. When there are multiple failures together, this is much more likely to lead to an accident. When there's just a single problem and it's handled with no loss of life, they don't write a report about it.

I agree, the stick shaker gets a pilot's attention. What the stick shaker tells the pilot is that he's about to stall, but that's not what was happening. Shaking the stick is loudly yelling false information at the pilot!

Let's look at the epistemology here. If we're only looking at the two AoA indicators, and one reads 5 degrees and the other reads 25 degrees, we know that there has been a sensor failure. All you can say that the airplane does not know what its angle of attack is. That's fine though, we've been flying planes for a hundred years without AoA indicators, even ones that had way worse pitch instabilities than the 737MAX. If the airplane doesn't know the angle of attack, there is no reason for it to activate the stick shaker, put in nose down trim, or do anything else except to calmly notify the pilots that AoA is unavailable and therefore MCAS is disabled. All the pilots need to do then is fly the plane normally and not do any crazy banked turns or extremely abrupt pullups at low speed. It's definitely wrong for the plane to start dialing in nose down trim "just in case", because the "just in case" can kill you if it's not necessary!

On AF447, there were as usual, a lot of mistakes made. One problem clearly though was that the plane was giving the pilots a lot of conflicting information that confused them. If the plane was seeing three different airspeeds, the best thing for it to do would have been to put a big red X over the airspeed tape and let them fly by pitch and power. This is exactly why a lot of instrument pilots in older smaller planes carry a little instrument cover. If say your AI fails in IMC, you don't want to see the wrong indication at all, so you cover it up and use your other instruments. Seeing a wrong indication, even if you know it's wrong is very confusing and can lead people to make errors in reasoning, especially in a stressful situation.

</comment></comment></comment></comment></comment><comment><USER21> From the article, "Outside the plane, one of the plane's angle of attack sensors falsely indicated that the plane's nose was pointed too high, and the aircraft could stall."

I'm not in any way eligible to comment on aviation systems, but why that equipment needs to measure the angle of airplane be outside? Couldn't something like gyroscope mounted inside do the job?

<comment><USER22> It's measuring the angle of the plane relative to the air moving past it (i.e. the angle the plane is "attacking" the air). Knowing the angle of the plane in an absolute sense isn't as useful when it comes to detecting stalls, etc.

<comment><USER23> It's not as useful but it is far from useless. The ordinary artificial horizon indicator should have been able to show that the external sensor was far out. I don't know anything about the aircraft or Boeing but as a software designer and implementor I would have wanted to use the output of the artificial horizon as well as the angle of attack sensor in an attempt to gauge the quality of the readings. I'm guessing here but it seems likely the aircraft was equipped with a normal gyroscopic instrument in addition to the external angle of attack sensor.

Of course the Boeing engineers who worked on this could easily tell us exactly how it works and why. I don't suppose that will ever happen though.

<comment><USER24> I think the problem is that moving air (such as an updraft) can alter the angle of attack independently of the pitch angle. That is important during landing where low thrust levels are set and the air is turbulent. But in other phases of flight it should be possible to keep the aeroplane stable using know thrust and pitch settings and ignore air speed and AOA sensors completely. Of course that requires fully functional control surfaces and engines. Maybe it would be better to remove the erroneous sensor type completely and have procedures that can cope with that.

</comment></comment></comment></comment><comment><USER25> I'm amazed that Boeing isn't the focus of more - much, much more - criticism. It seems clear to me they are vastly more culpable than the pilots or airline.

<comment><USER26> I agree that Boeing's share of responsibility is big. I think media coverage has largely reflected it too. I don't recall reading any article where it put the blame on the pilots. Based on what I've read, it felt more like, 70% Boeing, 29% airline, 1% pilot.

<comment><USER10> If this is the case we seriously need to consider getting rid of the pilots. Stab trim issues are a memory checklist item under existing training with clear cutoffs easily available.

1% pilot fault is ridiculous.

<comment><USER6> "Getting rid of the pilots" has already mostly happened. You know this. Autopilot on at 400-1000' and off at MDA/200'/DH to rollout. In between they are system administrators. Heck, even I can and often do fly my much smaller planes this way. And, as you also probably know, autopilot is required to be flying the plane above 28,000' (Google RVSM for interested readers).

I am sometimes glad I have access to Cubs, Decathlons, and other simple planes to keep me an honest pilot. :)

<comment><USER10> So true, and overseas actually a bigger issue I think because they don't always have the recreational / GA flying world going on. Some pilots in airlines trying to develop local skills are going basically straight onto an Airbus flight deck. Not saying it's bad, but they don't seem as comfortable with manual flying. And frankly manual flying is more complicated on these planes - the number of autopilot and throttle modes etc etc - a cessna - pitch, power... I do wonder if adding a basic safe flight pitch power button (ignores everything and just goes to a safe pitch power setting smack in middle of power curve) might help. Literally ignore AoA, ignore speed, ignore everything. Just trim to middle and set power. Air france? This flight? These planes are flying fine otherwise. You don't 100% need all the automation (though the MAX did introduce some weird instability near stall which is annoying in a big way). My own view - make a naturally stable plane (MAX moved away from this), and have a way to fall back to a basic setting that takes advantage of that.

</comment></comment></comment></comment></comment><comment><USER9> What the plane did here is not technically reasonable. We had optimal estimation and sensor fusion in the sixties. With two AoA sensors, three pitot/static systems, GPS, and a full IMU, the plane had more than enough information to determine that there was no high AoA situation requiring its intervention.calling for the computer's intervention.

Since this dangerous high AoA situation is so rare, even a simple rule requiring both AoA sensors to agree that AoA was dangerously high to override the pilot completely solves the problem. Even with just one AoA sensor and a little memory, the simple fact that the system had rolled in so much nose down trim, which should have lowered AoA, with no apparent effect should have clued it into the fact that it's model of the system was wrong and caused it to stop.

This is not a particularly sophisticated insight. The engineers all knew this when they designined the system. They had a reason for doing it the way they did, though, and that was to slip the new system in a bit under the radar of the FAA. Since the MCAS is required to maintain the stability of the plane at high angle of attack, it should have been certified as a Stability Augmentation System. That would have subjected it to more redundancy requirements and eliminated this failure. The problem was that Boeing wanted the MAX to not require significant training or certification beyond the 737/737NG. A big new Stability Augmentation System would have required extra certification and probably pilot training. Instead, they chose to sort of launder this system through an existing one, the Elevator Feel Shift system. The EFS adds some nose down trim at certain speeds and altitudes to make the 737NG feel like a classic 737.

Since the FAA already determined that the EFS wasn't a stability augmentation system, but it could control the elevator trim, Boeing figured they could piggyback the new MCAS onto it, adding just one new input, the AoA sensor, and no new outputs. Since it only controlled the trim and not the main flight controls, Boeing could keep to its manual control philosophy, and they could slip it through certification. They couldn't give the computer both AoA inputs, because the air data system is supposed to have two totally independent and manually selectable sets of sensors. If you give a computer both AoA inputs, you lose that redundancy concept.

So why did the EFS system never cause any problems despite having the same lack of redundancy? My guess is that the EFS is essentially an open-loop controller. It applies a fixed amount of forward trim for a given speed/altitude combination. If the pitot/static system goes haywire, the worst that happens is fixed, moderate amount of nose down trim, easily and naturally compensated for by the pilot or autopilot. The MCAS appears to be closed loop in that it will just keep adding more and more nose down trim until the AoA sensor says things are OK again, the pilot pulls its circuit breaker, or the plane smashes into the ocean.

People in the industry blaming the pilots one bit are making a mistake the industry collectively stopped making seventy years ago. We don't blame the pilot anymore, we blame the system. Given enough time, humans will make any mistake that can be made. If the plane cannot be flown completely safely by significantly below average pilots, it's an unsafe plane. Demanding that the system be safe even with imperfect pilots is why commerical aviation is so amazingly safe today. It's also ironically why the MCAS is in there in the first place. Boeing could have just put in the manual to never exceed 14 degrees of AoA, and even average pilots would never have a problem. The FAA would never certify such a plane to carry paying passengers with such a limitation though. It would be too dangerous. Eventually someone would screw up and the plane would go out of control, so there had to be a computer to prevent this. As it stands, the plane does not IMO meet certification requirements for the transport category, and the only reason it isn't grounded is because there are literally half a trillion dollars worth of these things in service or on order. I'm racking my brain to think of another single product produced anywhere that is so valuable.

<comment><USER27> I agree that that more focus should be placed on the system, however, with so many NTSB reports naming "pilot error" as the cause of accidents/incidents, I think we're still very much focused on the the pilots.

<comment><USER13> GP says it all right here,

>>> People in the industry blaming the pilots one bit are making a mistake the industry collectively stopped making seventy years ago. We don't blame the pilot anymore, we blame the system. _Given enough time, humans will make any mistake that can be made._

Excellent rundown by cameldrv all-around. Framing this a bit of certificatory sleight-of-hand is spot on, far as I can tell.

</comment></comment></comment><comment><USER28> All these years of listening to Boeing bigots talk about how bad Airbus planes are because they are too automated, flown by machines, unsafe.. And then a Boeing automated system seems to a significant cause of a fatal accident. Not sure what if any conclusion to draw from that, just the context.

</comment><comment><USER29> Would it be possible to have a single switch that disables all automatic systems and puts the plane in complete manual control as much as possible? Can these planes even operate in a complete manual mode?

<comment><USER30> Certainly possible but not required. In the B737 family, most of the main controls are essentially power assisted direct controls.

Boeing consistently has preferred more-or-less manual controls, while Airbus took the other direction (in which the pilot guides the computer, which operates the controls).

All airlines can fly happily in completely "manual" mode. Boeings are doing this most of the time, Airbus's only do this when the situation is outside the computer's envelope.

</comment></comment><comment> BXLE_1-1-BitIs1 There was an erroneous stick shaker that captured the crew's attention and diverted attention from the trim stuffing the nose down. The NYT graphics show a miniscule part of the problem. Most likely the FDR data has been played through a full motion simulator - it would be a hairy ride, but the crews have to keep it confidential until the Indonesian authorities release the data.

</comment><comment><USER31> [https://outline.com/pELX5F](https://outline.com/pELX5F)

</comment><comment><USER32> It doesn't feel like the NYT is trying to communicate something to their reader. Or if they are I can't figure out what the message is.

Apart from the whizzbang combined with tiny paragraphs (making it hard to read or comprehend), not all the text is available to Safari's reader mode.

</comment><comment><USER33> Both inconsistent readings and a plane actively working against the pilots will.

That seems like a pretty massive failing on the manufacturers part.

<comment><USER10> Except that runaway trim is a MEMORY checklist item.

Literally - they should have the procedure here memorized, and there are LOTS of cutout options, from temp right at fingertips to cutoff switches.

<comment><USER33> The fact that the FAA issued an emergency order with instructions after this crash suggests to me this wasn't sufficiently covered by existing procedure. In fact:

> The FAA's directive orders airlines within three days to update flight > manuals to include specific steps pilots should take to recover.</comment></comment></comment>


A 'Null' License Plate Landed One Hacker in Ticket Hell - <AUTHOR> https://www.wired.com/story/null-license-plate-landed-one-hacker-ticket-hell/ <comment><USER2> [https://news.ycombinator.com/item?id=20676904](https://news.ycombinator.com/item?id=20676904)</comment>


This Is Why There Are So Many Ties in Swimming - <AUTHOR> http://regressing.deadspin.com/this-is-why-there-are-so-many-ties-in-swimming-1785234795 <comment><USER2> TL;DR the tolerance in length of pool lanes doesn't allow for thousandth of a second timing resolution. That is, one swimmer's lane might be shorter within the margin of error that allows them to finish faster by a few thousandths of a second.</comment>


Justice Department audit finds widespread flaws in FBI surveillance applications - <AUTHOR> https://www.politico.com/news/2020/03/31/justice-department-audit-finds-widespread-flaws-in-fbi-surveillance-157166 <comment><USER2> "Never Attribute to Malice That Which Is Adequately Explained by Stupidity"

<comment><USER3> "Never assume that the stupid are incapable of being driven by malice."</comment></comment>


[Show HN] MAP - (Indian) MPs Attending Parliament - <AUTHOR> http://opinionatedindian.org/MPAttendance/

<comment><USER2> Wish every country had something like this.

Maybe you should show the aggregate as well. It is difficult to find out what percentage of "MPs" attended a session.

<comment><AUTHOR> Good suggestion pdevr.

Updated with the aggregate information (in each session). Aggregation overall is a pending task.

<comment><USER2> Awesome. There seems to be a bug: the numbers for "> 75%" and "< 65%" look like they're the same?

<comment><AUTHOR> Yes. A Twitter user pointed that to me. Fixed now.</comment></comment></comment></comment>


Effects of the x86 ISA on the Front End: Where have all the cycles gone? (2001) [pdf] - <AUTHOR> https://www.eecs.umich.edu/techreports/cse/01/CSE-TR-440-01.pdf <comment><USER2> The creation date of the PDF is 2001, so this is an extremely old paper and the details may not have all that much relevance anymore since x86 CPU development has progressed very quickly; I'd guess that AMD and Intel have already made use of the techniques mentioned here.

It's still worth reading though - the uop decoder mechanism of microarchitectures today remains very similar to that introduced with the P5, just wider and deeper.

</comment><comment><USER3> The paper's main problem is that they have to second guess all of Intel and AMD's design decisions. And it looks like they got some important things wrong, which makes their conclusions suspect.

For instance they claim an ADD mem, reg instruction would be translated into three 3 uops. This is definitely not the case, x86 chips can do a load+arith_op or a store+arith_op in the same uop. The reason they need to do this is because the old x86 (in the pre-AMD64 days) had only 8 registers so spills were very common and so loads and stores were very frequently executed, much more so than in RISC code. This meant that getting maximum performance out of the memory subsystem was very critical for x86. I remember an AMD chief architect telling me that the hardest part of building a performant x86 core is getting the memory subsystem right.

Anyway, back to the paper, I'm not terribly impressed. The uops/instruction number looks bogus. I remember those numbers being very close 1. The cycles per uop of 0.37 seems wildly optimistic. I remember numbers closer to 1.

My only caveat is that my experience working on x86 is from about 3-4 years ago. Maybe things were very different in 2000, but I doubt it.

<comment><USER2> _I remember an AMD chief architect telling me that the hardest part of building a performant x86 core is getting the memory subsystem right._

Definitely; Linus also makes this point in his well-known post on x86 ([http://yarchive.net/comp/linux/x86.html](http://yarchive.net/comp/linux/x86.html) ):

 _The low register count isn 't an issue when you code in any high-level language, and it has actually forced x86 implementors to do a hell of a lot better job than the competition when it comes to memory loads and stores - which helps in general. While the RISC people were off trying to optimize their compilers to generate loops that used all 32 registers efficiently, the x86 implementors instead made the chip run fast on varied loads and used tons of register renaming hardware (and looking at _memory_ renaming too)._

More recently, I've heard that the effectiveness of caching, out-of-order execution, and speculation mean that on modern x86 the most frequently accessed memory, which would be the local variables near the stack pointer, is almost as fast as the registers - comparisons have been made between the x86's 8 (or 16 for x86-64) registers and the 256 bytes around the stack pointer to the 6502's "one really fast register, and 256 others that are nearly as fast."

 _The uops /instruction number looks bogus. I remember those numbers being very close 1._

It depends greatly on the exact instruction mix being executed; same for the cycles/uop.

<comment><USER4>
      Definitely; Linux also makes this point in his well-known post on x86

Linus, perhaps?

<comment><USER2> Yes I do mean him. Fixed.

</comment></comment></comment></comment><comment><USER5> I am unclear when this was published. It does not reference an Intel microarchitecture past P6 (Pentium Pro) and contains no citations later than 2000.

TLDR Abstract: _We look at 8 aspects of front-end that can contribute to performance loss; then based on this information, we introduce an improvement that yields 17 % speedup in overall execution time._

<comment><USER6> It's from 2001. See: [http://www.eecs.umich.edu/eecs/research/techreports/cse_tr/d...](http://www.eecs.umich.edu/eecs/research/techreports/cse_tr/database/reports.cgi?01)

<comment><USER7> Thank you. I searched earlier and that information is surprisingly hard to come by.

<comment><USER6> Yeah, it's weird that the document doesn't "self-identify" its publication information anywhere. The only reason I found the metadata quickly is that I glanced at the URL and realized it was a tech report, so Googled for Umich CSE's tech report archive.</comment></comment></comment></comment>


Framework Patterns - <AUTHOR> https://blog.startifact.com/posts/framework-patterns.html <comment><USER2> Excellent article describing common design patterns used by frameworks, with examples and trade-offs/drawbacks discussed.

A framework is defined as "code that calls your (application) code". Not sure I totally agree, since frameworks that I've built are usually instantiated by the application explicitly. Well, that launch sequence is one of these patterns described.

Here's a table of contents.

\- Callback function

\- Subclassing

\- interfaces

\- imperative registration API

\- convention over configuration

\- metaclass based registration

\- language integrated registration

\- DSL-based declaration

\- imperative declaration

\- language integrated declaration

(Nitpick: might want to standardize the capitalization of titles, like "Pattern: Callback Function".)

<comment><USER3> I agree totally with "Metaclass based registration" as I have seen the same with Django Models. It took some time initially to grasp what(and when) is happening under the hood. Even now, I find it hard to make newcomers understand how it all works. I have taken 2 sessions with my current interns and still they get lost.

<comment><USER2> From the article:

> When you declare a Django model by subclassing from its Model base class, > Django automatically creates a new relational database table for it.

That sounds convenient - but feels like too much implicit behavior for me. I almost always prefer a framework that lets (or forces) the user to explicitly specify operations.

Same with "import-time side-effects". When I find myself providing such a shortcut, I usually wrap it so the user must call it explicitly, to control what/when these effects happen.

<comment><USER4> This is handwaving a bit, you still have to manually create the migration that results from your model code change, and also apply the migration.

It's "automatic" because you just have to issue a single command for each, and django generates the migration from your code and settings.

</comment></comment></comment></comment><comment><USER5> Great article.

I'm always a bit ambivalent about assigning "hard and fast rules."

In my mind, a "framework" is...a framework.

Frameworks are structural artifacts. They exist in the corporeal world, as well as CyberWorld. Buildings are constructed over frameworks. Vehicles are constructed over frameworks.

I have been writing SDKs, APIs, frameworks and drivers for a long time.

<opinion type="mine">

I tend to differentiate them (in my head) like so:

 _DRIVER_

Code/binary asset that affords a connection between two levels of a dynamic system; abstracting characteristics of the lower part of the system.

Drivers can exist at many layers; from machine-code to UI. I have written UI component drivers, as well as device drivers.

Drivers tend to be "smaller" projects than frameworks, but there's a lot of similarity between drivers and some types of frameworks.

 _API_

The published specification that defines interaction with a code/binary asset; combined with a minimal level of exposed code to afford access to the API elements.

 _SDK_

A code/binary asset that exists independent of an API, but which affords access to that API; often adding functionality.

I feel that an SDK can def be a framework.

 _FRAMEWORK_

Fairly similar to what was defined. maybe a bit "looser."

This is a set of code assets (not necessarily binary, but it's possible) that can be used as a "seed" or integral component of a code application (small "a," not necessarily a complete executable application -it could be a driver, SDK, operating system or framework).

In my mind, frameworks can be complete, self-contained and closed; possibly exposing only an API as an affordance to access the assets. Cocoa is an example. A framework can also be completely open-ended, and unusable without components provided by the implementor. Classic app frameworks like Qt are examples of this.

It may be open-source, or opaque.

The frameworks that I have written have been fairly large.

I feel that Drupal or WordPress can be considered frameworks, as well as things like Qt or Cocoa.

</opinion>

</comment><comment><USER6> So then React is a framework?

<comment><USER7> I would say yeah.

I think React calls you (render + callbacks) more than you call it in most cases.

Like a library, however, your code is usually kicking things off by calling ReactDOM.render().

I'm sure there are "meta-frameworks" build around react which set up your router in declarative style and call that top level method.</comment></comment>


Colombo, Sri Lanka: 6m Internet properties now faster for 6m Internet users - <AUTHOR> https://blog.cloudflare.com/colombo/ <comment><USER2> As I know, Cloudflare is the 4th CDN to add a POP in Sri Lanka. joining Google(Youtube), Akamai, and Facebook.

CDN caches are very important to Island countries like Sri Lanka because almost all of the data has to go through submarines cables, which are very costly and adds latency.</comment>


Ask HN: The black bar of HN's top navigate bar - <AUTHOR>

http://imm.io/1b8tt<p>I just notice there is a black bar on the top bar, does that mean R.I.P Doug ? <comment><USER2> discussion: [https://news.ycombinator.com/item?id=5987720](https://news.ycombinator.com/item?id=5987720)

<comment><AUTHOR> thanks!</comment></comment>


Fake apple stores - <AUTHOR> http://birdabroad.wordpress.com/2011/07/20/are-you-listening-steve-jobs/ <comment><USER2> _We struck up a conversation with these sales guys who, hand to God, all thought they really worked for Apple._

Now I'm wondering how I know who _I_ work for.

Now I'm wondering if I could have faked this entire blog post by photoshopping up some pics of a real Apple Store.

Now I'm wondering if I've been reading too much Philip K. Dick or too little.

<comment><USER3> these look like apple distributors though. as the products are apple original right ?

or are they using second hand apple products ?

<comment><USER4> I suspect they're using "second hand" Apple products. If you know what I mean. Nudge, nudge, wink, wink, say no more.

</comment></comment></comment><comment><USER5> _I seriously thought that it had simply been torn down and replaced with a bank in the mean time – hey, it's China. That could happen._

It used to be "Only in America" that the world muttered in disbelief. This century, I'm thinking "Hey, it's China. That could happen" might just be the new black, as it were.

<comment><USER6> Were we Americans this crass and exploitive in the late 1800's? Not rhetorical, but a genuine question. I've heard the opinion expressed that we indeed were.

<comment><USER7> America used to be notorious in the 18th and 19th centuries for ignoring copyrights and patents filed in Europe.

For example:

"Johns describes how the first generation of American publishers came to constitute themselves as book pirates who openly violated British copyright law by systematically reprinting works that the British publishers considered their own lawful property. This laid the foundations for a vital but highly controversial book market in the new world and Johns concludes that by "the 1820s, Jacksonian America had a secure and vibrant public sphere – but to European eyes an utterly piratical one".

Source: [http://web.mit.edu/comm-forum/mit7/papers/Fredriksson- Draft-...](http://web.mit.edu/comm-forum/mit7/papers/Fredriksson-Draft- MiT.pdf)

<comment><USER8> Evidence that our current intellectual property regime is simply not practical in a quickly emerging economic powerhouse?

<comment><USER7> I think it's more a result of the fact that China produces little intellectual property of its own right now. Enforcing copyright would raise costs, hinder development of copycat industries, and deplete the mountain of foreign exchange they've accumulated through exports. In addition, unlike most small countries that don't have domestic IP industries, China is not susceptible to US and European pressure.

The US eventually became a champion of IP laws once its own IP industries became globally dominant. China will discover the joys of copyright and patent lawsuits once they dominate the IP industries.

<comment><USER9> "once they dominate the IP industries"

Well English isn't the primary language there, that should probably make a difference in how things play out compared to the US.

EDIT: (compared to the US pirating British works)

<comment><USER6> From what I've seen, the Chinese don't "get" the aesthetic systems of other cultures as readily or completely as the Japanese did. The Japanese seem to have a distinct edge over everyone else in East Asia in this regard.

</comment></comment></comment></comment></comment></comment></comment><comment><USER10> When I was in China in 2006 I wondered into a fake Nike store of similar quality (In a residential neighborhood of Beijing). I too thought it was a real store, the only thing that gave it away was when I actually picked up the shoes in the store, I noticed all the swooshes were upside down!

Almost seemed like a waste to go through the whole effort of knocking off an entire store, only to fill it with obviously fake merchandise.

</comment><comment><USER11> I misread the title as "Fake apple _stories_ " and thought "how interesting can that be?"

Very, it turns out. It seemed a shame in cultural terms that saying "We work for Apple in the US and are making an on-site inspection" was enough to convince security to respect them, but actually, if you have the balls to pull it off, I bet that would work anywhere.

<comment><USER12> I figured that some of the higher-level employees would have to be in on it, and any people from the REAL Apple would send them into a panic. In this case, maybe all the store employees, from top to bottom, really were clueless.

</comment></comment><comment><USER13> This reminds me of how Tower Records opened their first store in Japan, when a fake Tower Records store was already operating in Sapporo... (see [http://www.fundinguniverse.com/company-histories/MTS-Inc- Com...](http://www.fundinguniverse.com/company-histories/MTS-Inc-Company- History.html)) Interestingly enough, the Japanese branch became independent a few years ago and is still in business, when the US stores have now disappeared.

</comment><comment><USER14> This is simply amazing. I can only imagine how quickly these initial stores will be closed down. They will spring up again like weeds, but these first ones will be probably be closed with in a few weeks.

I really love that last picture with the spelling mistake "Apple Stoer".

</comment><comment><USER15> I have actually been in a fake Apple store. It was eerie. Same decor, the staff all wore the same tshirt uniforms...amazingly, they had set up shop within sight of a real Apple store, in a big mall in Denver. The only real giveaways that it was not real were that they had these big-ass multitouch tables with $10k price tags and there were very few customers in the store.

</comment><comment><USER16> I feel really terrible for the employees who work at these stores, thinking they are working for Apple. I think about how I felt when I got a job I really wanted at that age, and the joy they must have felt when they were hired, and telling all of their friends and family that they were Apple employees.

Look at the photos of the employees. They look so sincere and earnest. I can only imagine the disappointment they will feel one day when they find out they're working for a con man.

I'd love it if this story ended with "and then Apple, seeing how badly Kunming wanted to have an Apple Store, came along, built a real one, and hired all the employees at the new, legitimate store."

<comment><USER17> Real, legitimate Apple products are going to be something like six times more expensive than the counterfeits.

It's not out of pure malice that prevents Apple from segmenting markets-- if the iPad sold in China is too much cheaper than the iPad sold in America, then people will just purchase iPads by the thousand to resell them in America.

</comment></comment><comment><USER18> Doesn't actually say whether it sells actual Apple stuff, or knock-offs, or if it did I missed it.

<comment><USER19> of course it's actual apple stuff, it comes from an actual apple store.

</comment></comment><comment><USER20> Yay for yet another interesting blog post wrapped in OnSwipe's miserable, unnecessary iPad theme.

<comment><USER21> Yeah, I have to say I don't quite get the point of that. The original WP theme would look absolutely fine on an iPad. Otoh, the onswipe theme looks a bit weird and has annoying scrolling issues, and takes ages to load too. Not quite sure what it adds to anything other than a vague sense of frustration...

</comment></comment><comment><USER22> How do the people doing these knockoffs miss the little details like "stoer"?

They're obviously putting a tremendous amount of work into the clone, is hiring a native English speaker to look at it and make sure the English looks like English _that_ much of an extra expense?

When I'm sending posters and promotional materials to our printer (as in: the company that does printing, not the device), I go over it again and again, then usually get a second and third set of eyes to triple check it for spelling errors.

These knockoffs are really _good_ , it's kindof sad that they're so close, but missing it with the little stuff.

Or do they not really expect any English speakers to show up? If that's the case, why the English words at all?

<comment><USER23> > Or do they not really expect any English speakers to show up? If that's the > case, why the English words at all?

Because it makes the store look trendy and sophisticated. Sort of like how many Americans will think some product is "upscale" if it has a French name or the voiceover actor in the ad has a British accent.

<comment><USER24> Yeah, if you go to a French bakery in the USA, and everything is labelled in French and in English, does it even matter if the French is correct?

</comment></comment></comment><comment><USER25> It looks like they are selling genuine Apple products. So the only thing this store is guilty of is using the "Apple Store" name without permission. There is nothing illegal about running a store that sells only Apple products, and decorating it in a matching way. It is quite common in China to see small stores that sell only Lenovo, only Dell or only Sony products, and they are not usually run by the brands.

<comment><USER17>
      It looks like they are selling genuine Apple products.

Oh please. What evidence are you basing this judgement on, the blurry cameraphone pictures from this blog post? Magic? Intuition that of _course_ a counterfeit store, operated by a third party, will only carry genuine items?

<comment><USER26> Actually, what would a counterfeit macbook look like? An amumimum colored generic laptop running XP with some OS X theme?

I have seen videos of ( _very_ obviously) fake iPhones, where they look pretty real until you start using it.

Would they actually sell anything if all they had was obviously fake crap?

</comment></comment></comment><comment><USER27> Funny I should see this today. I was just reading the wikipedia page on "Simulacra and Simulation":

"Simulacra and Simulation is most known for its discussion of images, signs, and how they relate to contemporaneity. Baudrillard claims that our current society has replaced all reality and meaning with symbols and signs, and that human experience is of a simulation of reality. Moreover, these simulacra are not merely mediations of reality, nor even deceptive mediations of reality; they are not based in a reality nor do they hide a reality, they simply hide that anything like reality is irrelevant to our current understanding of our lives."

Edit on further thought:

If the products are the same, how is this more 'real' than a genuine apple store? They are both just a collection of signs, branding, processes and marketing.

What happens when stores in even smaller towns spring up, copying this fake apple store? What then is the reality? How far along do the copies of copies need to go, before they are totally divorced from the originals in America? Do they then become 'real' and genuine their own right?

</comment><comment><USER28> I'm wondering if this isn't a real Fake Apple Store... as in, Apple recognizes the need to develop that market and also recognizes the fact that their products are prohibitively expensive for those customer - to avoid diluting the Apple brand, build "Apple Stoers" selling the merchandise at a deep discount.

These new Apple Stoers would be very functional and serve the company on many levels. Quickly test new markets with low risk, introduce the Mac at a lower price point, and eventually could be replaced with Real Apple Stores in strong markets.

As the Chinese economy develops, the price of the merchandise increases (maybe shifting from store to store?) and in a few decades they have a stronghold on the edgy cool market of top-of-the-line-computers in the new world market, but also have one on the lower-end Apple Stoer brand.

Sounds like a good plan, just seems strange that we're all talking about it though...

</comment><comment><USER29> I was in this "Apple" Store 2 weeks ago (I live in Kunming). They didn't have the airline magsafe adapter in stock.

The thing that gave it away for me (besides it being in _Kunming_ ) was the non-Lucida-Grande typeface everywhere.

If anyone wants me to go in there next week when I get back to the mainland, let me know.

</comment><comment><USER30> Are these fake apple stores selling genuine apple products? Or the products themselves are fake?

</comment><comment><USER24> A lot of the official Apple resellers in non-US countries have also lifted the entire Apple store look -- wood tables with products, white walls, lots of glass, white banner signs. The only difference is they don't call it an Apple Store.

</comment><comment><USER31> There are countless examples of this. I too was amazed at how widespread the cloning was when I visited China. I recall this massive 'Hazma 6' billboard along one highway in Shanghai and being warned not to drink a particular bottle of water in Dalian. Who rips off bottle water? China!

Who can forget the ripoff X5 that they attempted to put on display in Frankfurt? (<http://goo.gl/oPD5y>) BMW wasn't having it.

Oh, have you seen the poorly cloned Disney World? (<http://goo.gl/DO6Ii>)

</comment><comment><USER32> I don't get it: do they (re)sell genuine apple products or ripoff too?

<comment><USER12> Most likely they are selling genuine products stolen from the factory or shipping containers.

<comment><USER33> What are you basing this on?

</comment></comment></comment><comment><USER34> Somewhat related: [https://plus.google.com/108481435543473632495/posts/aQJGcM3L...](https://plus.google.com/108481435543473632495/posts/aQJGcM3L4dx) (pizzeria in China)

</comment><comment><USER35> Well, it's more convincing than the last time:

<http://www.wired.com/gadgetlab/2007/10/fake-apple-stor/>

</comment><comment><USER36> They're gonna be raided like meth labs once Apple gets wind of this (if they haven't already).

<comment><USER37> I seriously doubt the Chinese police will care. Maybe if it was in a city where Apple had a factory and they had cultivated relationships with local officials, but out in the boonies they have no power.

<comment><USER38> Kunming is a huge tourist city that a lot of Americans go to when they visit China. This makes it easier for Apple to put pressure on them.

<comment><USER37> Maybe slightly, but no more than it would be for some chinese company to put pressure on the local police in San Francisco, and likely quite a bit less.

</comment></comment></comment></comment><comment><USER39> how long has this gone unnoticed</comment>


AppFog: Tunnel to your database from your dev machine - <AUTHOR> http://blog.appfog.com/manage-your-appfog-data-from-your-workstation/

<comment><USER2> How is this any better than using SSH tunneling?

<comment><USER3> SSH tunneling is not possible in PaaS environments.

<comment><AUTHOR> Or more directly, there is a high impedance mismatch between PaaS and existing SSH server solutions, for my reasons above.

I'm not giving up on SSH for CloudFoundry altogether, but Caldecott is an elegant solution that fits our constraints and solves one of our customers' problems.

<comment><USER4> I don't know if I'd go so far as to say TCP over HTTP is an "elegant solution" but it works well enough in the absence of SSH.

The Stackato client supports this now as well.

[http://www.activestate.com/blog/2011/12/new-stackato- client-...](http://www.activestate.com/blog/2011/12/new-stackato-client- tunneling-and-https)

</comment></comment></comment></comment><comment><USER5> This issue of why you couldn't do this before is that you don't have a shell account on AppFog/PHPFog machines.

</comment><comment><USER6> I've always just used SSH for this.

</comment><comment><USER7> SWEET</comment>


Mapping the Human Exposome - <AUTHOR> http://alliance.nautil.us/article/242/mapping-the-human-exposome <comment><USER2> Personalized medicine is great if you want to charge people a lot of money for marginal results, or if you are in the sciences and your goal is full understanding of everything in human biochemistry.

But all the real, meaningful goals in medicine are basically the same for everyone, barring the very, very tiny number of people with serious genetic abnormalities. And even in their small genetically abnormal groups, the reason for their issues are the same for everyone with the same specific mutation.

99.99% of the population ages and suffers age-related disease for exactly same underlying reasons. The molecular damage is exactly the same. Ditto the pathogens that cause infectious disease. You tailor medicine to the pathogens, to the molecular damage, to the mutated gene in an inherited condition, not to the person. Rejecting personalized medicine is the most cost-effective way to proceed towards mass-manufactured, low-cost, effective medicine.

Fix the inherited diseases with gene therapy. Repair the molecular damage that causes aging. Build the technologies that effectively destroy pathogens. Don't focus on the tiny variations in individual responses to these things before you try to actually address the root of the problem. This is my complaint about personalized medicine in a nutshell: it is displacement activity, distracting from paths that will be far, far more effective in improving health and addressing medical conditions.

<comment><USER3> > But all the real, meaningful goals in medicine are basically the same for > everyone

I think your view is a bit narrow. For instance if you get cancer, the goal is "cure MY cancer." And like unhappy families, many cancers are broken in unique ways.

You might find the abstracts here interesting:

[http://www.immuno-oncologysummit.com/Personalized-Cancer- Vac...](http://www.immuno-oncologysummit.com/Personalized-Cancer-Vaccines/)

</comment></comment><comment><USER4> This is nothing short of a potential revolution. There are a wide number of illness in humans we don't understand, and have been making almost no progress on.

For example near-sightedness. We know it's more than genetic because rates have been skyrocketing, and we know time spent outdoors means lower rates of myopia, but that's about it...</comment>