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jlebar

3,806 karma · joined January 30, 2012

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jlebar··on There are only four billion floats, so test them all (2014)
Six Stages of Debugging

1. That can’t happen.

2. That doesn’t happen on my machine.

3. That shouldn’t happen.

4. Why does that happen?

5. Oh, I see.

6. How did that ever work?

http://plasmasturm.org/log/6debug/

jlebar··on Libcu++: Nvidia C++ Standard Library
This is super-cool.

For those of us who can't adopt it right away, note that you can compile your cuda code with `--expt-relaxed-constexpr` and call any constexpr function from device code. That includes all the constexpr functions in the standard library!

This gets you quite a bit, but not e.g. std::atomic, which is one of the big things in here.

jlebar··on Why has college gotten so expensive in the last 30 years? A blank check in 1993
If the private loans are guaranteed, what incentive do the private lenders have? That's my point.
jlebar··on Why has college gotten so expensive in the last 30 years? A blank check in 1993
The high end is for students who are "independent", i.e. not with their parents (or similar). This is a tiny minority -- they make it very hard to declare independence.
jlebar··on Why has college gotten so expensive in the last 30 years? A blank check in 1993
The central claim in TFA is that when the government gives out loans directly, instead of guaranteeing loans made by banks, it's easier for students to get student loans, and therefore college prices go up.

a) Zero evidence is provided in TFA that it is in fact easier for students to get loans under the government program. I could make an equally compelling argument and say, when the private sector provides loans guaranteed by the government, private sector has a monetary incentive to seek out students and pile them high with loans that they can't afford. The loans are guaranteed by the government, so more loaning is direct upside.

In contrast, the government has no incentive to partake of predatory lending! Its incentives are aligned -- and not just on the monetary angle, but also, the government does not succeed if students are stuck in debt forever. Therefore when government gives the loans, incentives are aligned and lending goes down.

I've provided just as much evidence as Andrew. I'm not saying I'm right, but how do we know he is, either?

b) Andrew who?

c) TFA neglects to mention that you can take out up to $5500-7500 in government loans per year as an undergrad. https://studentaid.gov/understand-aid/types/loans/subsidized... If they had, you might have doubted their claim that this is the reason that college costs $50+k/yr.

We are already under this dude's system of "government offers a small, fixed amount in loans and students have to figure it out". Prices are still high and increasing.

It turns out that the high cost of college doesn't have a simple explanation or solution. Who knew.

jlebar··on Greenland ice has shrunk beyond return, study finds
> 10% decrease in grain yield

Wikipedia has a good article: https://en.wikipedia.org/wiki/Climate_change_and_agriculture

One thing to consider when you're reading anything about the predicted effects of climate change: The effects will not be uniform in space or time.

For example, warming itself has been highly nonuniform. It's not that every day, every location on earth is X degrees warmer. Rather, that's an average; some days in some places are a lot hotter, and on other days in other places, it's less hot. This means that in addition to the average temperature increasing, extremes are also more common (has to be).

See the first picture at https://en.wikipedia.org/wiki/Global_warming, or this video: https://climate.nasa.gov/climate_resources/139/video-global-...

I expect that "10% decrease in average [time and space] grain yields" would also be spiky, in time and space. That means some places and times will experience significantly more than a 10% drop.

jlebar··on Numerical Linear Algebra for Programmers
> The reference you are looking for (includes executable C++) is Numerical Recipes by William Press et al.

I bought this book hoping it would be to floating point what Hacker's Delight is to integers.

It is not that.

I'm not really sure what it is. Most of the numerical algorithms I wanted weren't included at all. Those that were, like random number generation, were out of date and covered with much less rigor than you can find online with some Googling. IIRC their algorithm for generating a random float in the range [0,1] is just wrong.

The book does indeed include executable C++. But the C++ it includes is a travesty. It's C++ written by someone who sort of understood C.

Anyway I did not like it. :)

jlebar··on After GitHub CEO backs Black Lives Matter, workers demand an end to ICE contract
> But to expect that a _federal agency_ will be denied service from a private entity, especially for essentially political reasons, is lunacy.

I mean, it's also lunacy that the US government would run concentration camps, right?

https://nymag.com/intelligencer/2019/06/aoc-holocaust-why-mi...

https://www.esquire.com/news-politics/a27813648/concentratio...

The issue I take with your argument is, politics in the United States aren't "normal". Maybe they never were "normal". But I think the notion is, this is more than a "political" disagreement over whether the tax rate should be 23% or 25%. We're in the midst of a fundamental moral disagreement about whose lives matter.

jlebar··on Intel Discloses Lakefield CPUs Specifications
> The program machine code can be scanned when loaded to look for specific assembly opcodes to determine the required capability of the CPU to execute it on.

That works as a heuristic, but it's not perfect, since JITs and self-modifying code are a thing.

I expect the chip will raise a fault and the OS will move the process.

jlebar··on Fremont Tesla workers tested positive for coronavirus days after plant reopened
> We are doing what we can to mitigate loss of life.

Some individuals/business-owners doing what they can to mitigate loss of life caused by the reopening of their businesses, yes. Some people are wearing masks.

This is by no means universal. You don't have to go far to see videos from Vegas, or of airlines not enforcing their own mask policies.

And also, as a society we absolutely are not doing what we can to mitigate loss of life even within the parameters of a fixed amount of economic activity.

jlebar··on New inline assembly syntax available in Rust nightly
> 1. It’s the syntax in the manual. The last thing I want to do when reading or writing asm is to mentally translate from the manual to AT&T syntax.

Right! I worked on C++ compilers for years and I don't even know where is the canonical book of AT&T mnemonics. At the rate that Intel is adding new instructions, using anything other than their official docs (and thus their official names) seems nuts.

jlebar··on Fremont Tesla workers tested positive for coronavirus days after plant reopened
My point was to respond to your "what if there's never a vaccine? Will we hide in our homes forever?"

There's a middle ground between "no attempt made to mitigate the loss of human life" and "safe and effective vaccine readily available". We can and should be doing more.

It's also not too late to do more.

But instead, we seem to be adopting the nihilism that I read in your original post, that, (in a few ways) time's up.

jlebar··on Fremont Tesla workers tested positive for coronavirus days after plant reopened
> For how long? What if there is never a vaccine? Will we hide in our homes forever? [...] Lockdowns just can't last forever

Indeed. The purpose of the lockdown was to buy us time to build e.g. contract tracing infrastructure, massively expand testing, and develop other means to allow us to reopen safely.

Instead for the most part we've sat on our hands and done very little. Thus we're saying, well, sucks to be us, I guess we have to reopen and let people die.

It didn't have to be this way. It doesn't have to be this way. There is plenty of evidence of this from around the world.

jlebar··on Fremont Tesla workers tested positive for coronavirus days after plant reopened
> if they take reasonable precautions

Who decides what's reasonable? To me, "reasonable" might mean, "precautions that minimize unnecessary risk to human morbidity and mortality". Even if we were to agree on this, what do "minimize" and "unnecessary" mean? And how do we take into account second-order effects, like, maybe my workplace is primarily young people and there's relatively low risk of long-term harm, but my employees might spread the virus in the community...

> it is far easier to contain the issue in a factory floor than the supermarket

Although this claim has some logic to it, I'm not sure it is actually true. See the outbreaks at meatpacking plants, https://www.sltrib.com/news/2020/06/08/cache-valley-providin..., https://www.nytimes.com/interactive/2020/06/08/us/meat-proce...

That's the thing about this novel virus. There is a lot of uncertainty.

These are all hard questions. I'm not pretending that health officials have uniformly made the right call, or even good calls. I am saying that if you think it's as simple as stating the policy "let anyone taking reasonable precautions open for business", I have a bridge to sell you.

jlebar··on Slack Removed a Blog Post Showing How Police Use Its Tech
Here's a mass resignation, but in protest for officers being disciplined for shoving the old dude. https://mobile.twitter.com/GaryRidesBikes/status/12689856604...

Where are the good apples?

jlebar··on Slack Removed a Blog Post Showing How Police Use Its Tech
> I feel like this entire movement is really taking away credit from the "ok" and "good" cops.

I'd really like them to step up. Where's the intervention and condemnation from the presumed silent majority of good cops in any of these incidents?

https://www.theverge.com/2020/5/31/21276044/police-violence-...

Here's a video of an old man being attacked by police in Buffalo, https://www.nytimes.com/2020/06/05/us/buffalo-police-shove-p... How many of the presumed silent majority walked by him as he bled on the ground? How many have stood up and said, the people who did this don't stand for what I stand for. How many cops are demanding reform and threatening to quit otherwise?

The Buffalo police initially lied about how this man was hurt, claiming he "tripped and fell", https://twitter.com/JeffRussoWKBW/status/1268712651292643334.... Where's the condemnation of that from the officers who were on the scene? And even if we presume this guy gets justice, where's justice for the presumed many people who aren't sympathetic old white dudes whose assault was captured on camera? They would have gotten away with it if it weren't for the video, and indeed they may still get away with it.

Where are the police unions in taking a stand against this kind of violence?

I dunno, like you I don't currently believe that we should entirely eliminate police from our societies. But if the silent majority of good cops we presume exists isn't willing to take a stand against what is clearly evil in their ranks, how good are their actions, really? Kneeling doesn't get you very far.

jlebar··on Hundreds of Facebook employees walk out as Zuckerberg plans town hall tomorrow
So the difference is prominence, highlighting this one particular reply because it was written by the platform itself?

I'm still not seeing how this is a big deal. What are the second-order effects?

jlebar··on Hundreds of Facebook employees walk out as Zuckerberg plans town hall tomorrow
If you say something, and I say, here's some evidence that you're wrong, does that make me an arbiter of the truth on the Internet? I mean, how is what you did (saying something) any different from what I did (also saying something)?
jlebar··on Hundreds of Facebook employees walk out as Zuckerberg plans town hall tomorrow
Isn't the context also important for people to know?

Like, if the President of the United States is saying something that's factually incorrect and might cause people e.g. not to register to vote (because they expect every Californian will be getting a ballot), is that context not also significant?

Or, hypothetically -- but really if you think at this point that this is a stretch, come on -- if Trump claims without evidence on November 3 that he was the victim of massive voter fraud and the election was stolen, and calls for his supporters to take up arms against their state and local governments, should that be broadcast without context or commentary?

jlebar··on Organ donation in England has moved to an opt-out system
Can we agree that people will be harmed on both sides of this?

Like, if organ donation is the default, at the very best, it's extra work for people who want not to donate their organs after death.

OTOH if organ donation is not the default, dramatically fewer organs are available to people in need, and many of them will die.

How are we supposed to weigh these competing harms?

jlebar··on TSMC Announces Intention to Build and Operate Advanced Semiconductor Fab in U.S.
>> Remember when Trump floated withdrawing from NATO?

> I remember when Trump took no actions at all toward pulling the US out of NATO

In times of peace, alliances exist only in rhetoric. NATO has strength only insofar as people believe that member states will come to each other's aid. Trump called his commitment to the treaty into question, and in so doing made the alliance less strong. Surely you see this.

>> Remember when Trump stopped funding the WHO in the middle of the worst pandemic of the past 100 years?

> I remember when the WHO cooperated with China to knowingly lie about the pandemic, including trying to forestall borders from being closed, trying to forestall the isolation of China, lying about the nature of the virus including the risk that it posed, and committed global genocide in the process.

I mean, if lying abut the nature of the virus or the risks it imposed was grounds for dissolving an organization, then surely the federal government and many state governments should be dissolved by now.

But for the sake of argument, let's stipulate that what you wrote was 100% correct.

The WHO does lots of things. Apparently one of them is facilitating "global genocide" (kind of harsh?). Another one is helping countries, rich and poor alike, survive this very disease we're stipulating it brought into being.

Is America or the world safer today because the WHO lost its biggest funder? What replaces it?

If we don't want the WHO being unduly influenced by China, how does defunding it advance that cause?

jlebar··on Ask HN: What's your quarantine side project?
I've been building a tool to make it easier to upload chains of dependent PRs to github, https://github.com/jlebar/git-pr-chain

Works pretty well for me, but there are lots of ways it could be improved if anyone is interested in hacking on it with me.

jlebar··on TSMC Announces Intention to Build and Operate Advanced Semiconductor Fab in U.S.
> Welcome to USA. Smart Move TSMC and Taiwan. You have earned a friend for life.

Remember when Trump floated withdrawing from NATO?

Remember when Trump stopped funding the WHO in the middle of the worst pandemic of the past 100 years?

America First has no room for friends for life. Only friends for the moment.

jlebar··on Update to L.A.'s stay-at-home orders
> The only real choice is a mixed policy that just have strict guidelines for businesses serving customers.

How is this different from what the article proposes?

jlebar··on James Damore and three others end Google suit
Suppose we had data that we agreed was reliable showing that women software engineers who had read Damore's memo and Yonatan's post would overwhelmingly be unwilling to work with Damore and overwhelmingly be willing to work with Yonatan.

I'm not saying I have this data, but just hypothetically, suppose we did.

Would this at all influence your judgements (e.g. "deranged lunatic") of them? Why or why not?

jlebar··on James Damore and three others end Google suit
OK, if I'm understanding this right, the argument is that because the document was not initially printed in full (i.e. with figures and citations) in the press (and had inflammatory headlines), many people got the wrong impression about it.

That seems like a testable hypothesis.

1. If it were true, I'd expect a significantly higher proportion of Googlers to be on his side than the proportion non-Googlers, since all Googlers had access to the full memo. Is that true?

2. If it were true, I'd expect a significant number of people who ended up reading the whole memo to say, I initially had a negative reaction, but after seeing X specific figure or citation, I changed my mind. Has anyone in this thread said that? If not, why not?

(Is your feeling that first impressions are everything, and after that, people's views are ossified past the point of being able to change?)

jlebar··on James Damore and three others end Google suit
How does the fact that people criticized the memo without reading it in full speak to OP's point about the memo having been taken out of context?

I'll also suggest, reading this memo was incredibly painful for many of my female colleagues and friends inside and outside of Google. I don't think they should have to read the entire thing carefully in order to have an opinion on it. Indeed, I am not a well-read expert in many schools of thought that I nonetheless object to.

> Worth noting the first couple outlets (Vice, Gizmodo) did not post the full memo when they dropped the story.

OP's claim was that this was intentional with the goal of creating sensational clickbait. I guess the idea is, the full memo was tamer and, had it not been excerpted, people would not have reacted as strongly.

Do you agree with this?

jlebar··on James Damore and three others end Google suit
And to you this constitutes reporting that was "purposefully out of context and twisted in order to create rage click bait to satisfy someone's ideological crusade"?
jlebar··on James Damore and three others end Google suit
Literally his whole memo was posted online, in full. I struggle to understand the context that was missing.
jlebar··on James Damore and three others end Google suit
First of all, there are plenty of businesses that would do exactly this. It is legal in most US states.

OK, but I don't think it's right. Here's why.

We as a society have said, employers can "discriminate" (meaning "choose") employees on some axes but not others. They can discriminate based on where you went to college, where you've worked previously, how friendly you seem to be, but not based on your gender or race. That's true even if working with a Black person or a woman would make some people uncomfortable.

The question, which I'll leave as a question, is, what's the difference between these two sets, and in which one does LGBTQ identity belong and why?

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