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plesner

622 karma · joined August 4, 2013

Christian Plesner Hansen

Blog: http://h14s.p5r.org

Website: http://c7n.p5r.org

[ my public key: https://keybase.io/p5r; my proof: https://keybase.io/p5r/sigs/nc-O1JGHhVORXxZAziE3DK0gZLCDdNTbt8wfDXYmHR4 ]

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plesner··on Bigger Better Varints
This post was actually partly inspired by a HN discussion: https://news.ycombinator.com/item?id=40426666.
plesner··on The Mindlessness of Ostensibly Thoughtful Action (1978) [pdf]
Their model of scripts and mindlessness is only one of many possible explanations of the behavior they're seeing. And I don't even know where to start with the sending letters to random doctors thing.

Is this actually a thing that was/is taken seriously?

plesner··on PEP 760: No more bare excepts
If someone on my team or in my company proposed to break most of our python code for no substantial reason, unless they were pretty junior I would count that as a real red flag against their judgement.

How do people land on the python steering council exactly?

plesner··on The Fastest Mutexes
I'm very ready to believe your description of the state of python is true but I've been out of the loop on python for a while. I'm interested in more details. Can you expand or point to any articles that give more details?
plesner··on NASA is about to make its most important safety decision in nearly a generation
It's a diphthong though. Same as the difference between George (roughly dzo:rdz) and Geörge (roughly dze:ordz).
plesner··on CrowdStrike's Falcon Sensor also linked to Linux kernel panics and crashes
> I think blaming DEI hires for problems is mostly people who don't like the idea of hiring based on race/gender/etc. and who also realize that if you do that hard enough, you're bound to get inferior people because you're limiting your hiring pool.

Isn't that exactly the problem though: hiring is currently based on race/gender in favor of white/male hard enough that you get interior people from that hiring pool?

plesner··on Microsoft has serious questions to answer after the biggest IT outage in history
There seemed to me to be a clear shift in focus from CrowdStrike to Microsoft somewhere along the way, maybe a little while after George Kurz' message. I was wondering if it was either spin or the media collectively deciding that people understand what MS is better than CS.
plesner··on Welsh government commits to making lying in politics illegal
How much of a politician's time is taken up by making public statements of the type this kind of legislation covers? At least for someone in power, surely only a small part.

If we can't trust politicians to tell the truth in public statements then that's the smaller problem. The bigger problem is: what are they doing the rest of the time when not in public? What kinds of decisions are they making and how are they exercising power? Being a liar and being a terrible leader goes hand in hand. This gives the impression of doing something useful when the best case scenario is that awful people can continue to exercise power, they just have to be a bit more careful what they say in public.

The real question is, how do you prevent terrible people from ending up in positions of power. But avoiding that requires changing how people come to power which nobody in power wants to do. So we get red herrings like this instead.

plesner··on All I want for Christmas is a negative leap second
It makes a lot of sense to not care about a slight amount of drift. But that already exists: that's what TAI is. Why make UTC into another TAI just slightly offset? Why not just switch to TAI? Or, if the 37 second difference between UTC and TAI is the problem they can make a new TAI-minus-37.

What makes no sense is taking something useful, UTC, and redefining it out of existence. Then what time do you use if you really do care about drift? Do we invent a new UTC?

plesner··on vu128: Efficient variable-length integers
I implemented a slight variation of this a while back which worked as described up to 11110xxx but then a prefix byte of 11111xxx meant a payload of 64*2^xxx bits. So 11111000 is followed by a 64-bit value, 11111001 by a 128-bit, up to 11111111 which is 8192 bits.
plesner··on Regular expression matching can be simple and fast (2007)
This is a fine introduction to automata-based regexps but the framing of comparing "good" automata with "bad" perl-style is misguided. Automata and perl-style regexps are different beasts and solve different problems. The problem seems to be one of terminology: the perl style should never have been called regexps. That's not what they are. It's a pattern language that happens to have a variant of regexps as a subset.
plesner··on Infinite Craft
Future + Germany = Hitler

Plant + Germany = Beer

Flower + Germany = Hitler

(Harsh!)

plesner··on Infinite Craft
Some interesting finds.

Future + Time = Present (with a gift icon) Present + Present = Gift

(So it's using the words not the concepts)

Paradox + Snowman = Yeti

(Makes sense)

Arnold Schwarzenegger + Narwhal = Shwarzenwhaler

(Shwarzenwhaler has 0 hits on Google, it made it up)

Shwarzenwhaler + Time Machine = Hitler (with a crown icon)

(I kid you not!)

Unicorn + Hitler = Unihitler

(I continue to kid you not!)

plesner··on The microcode and hardware in the 8086 processor that perform string operations
Babbage's analytical engine used a form of microcode ~100 years earlier. Complex operations such as multiplication and division were implemented by lower-level instructions encoded as a series of pegs on a rotating barrel. Each micro-instruction ("vertical" in Babbage's terminology) could take several seconds to execute so a complete multiplication or division would take minutes.
plesner··on JEP 442: Foreign Function and Memory API (Third Preview)
This is an intricate API that is likely to require an intricate implementation just to be correct. But correctness won't be enough, the JEP requires the JIT to implement some complex optimizations.

I could use some reflections around: how do you implement such a large and complex feature in a JIT without potentially creating lots of vulnerabilities. It looks like a lot of new surface area in the VM with bad failure modes and VM engineers too are only human.

plesner··on Bitwise Division
Author her. I didn't run benchmarks. I'm suspicious of micro-benchmarks and I don't have a context where I can try it against realistic data. Also, I just enjoy the maths of it even if it turns out not to make a huge performance difference in practice.
plesner··on A record label bringing Iranian music to the world
I came across iranian classical music by accident years ago and keep coming back to it in a way I don't even with western classical music (I'm european). It's beautiful, highly skilled, passionate, and very much its own thing.

My starting point was Hossein Alizadeh and Masters of Persian Music (which also features Mohammad and Homayoun Shajarian). Unfortunately their albums come and go a bit on streaming services.

plesner··on On Summing Integers
Could you not just do

sum(byteVals) + sum(intVals) + 128 * len(intVals)?

plesner··on Sweden Drops Julian Assange Rape Investigation
It's possible to be both unfairly targeted by a superpower and commit sexual assault, one doesn't cancel out the other. I'm not saying he did, I don't know how any of us could know. You seem quite confident he didn't though, I'm curious what you base that on.
plesner··on What We Can and Can’t Learn from Copenhagen
They're not ridiculous taxes, they more or less match the immediate cost to society of private car ownership: maintaining the road networks, health care for people involved in accidents or sick because of pollution, etc. If car owners paid the indirect expenses as well, environmental impact, the value of the land occupied by roads and parking, etc, the taxes would be much much higher. Even in Denmark car ownership is massively subsidised.
plesner··on Facebook reveals its cryptocurrency Libra
Implied sarcasm and irony is a troll's game. Not to imply that the poster is a troll, I have no reason to think that, but that's why I never assume sarcasm if it's not explicitly stated.
plesner··on Facebook reveals its cryptocurrency Libra
No he doesn't, that is not what fiduciary responsibility means. See https://corpgov.law.harvard.edu/2012/06/26/the-shareholder-v...
plesner··on Google's interview system: it's not about solving the problem
I conducted many interviews while I worked at google and I wouldn't trust anyone who tells you the interview situation as one particular, well-defined, thing. Individual interviewers have their own style, approach, goals. Even if people start from the same place because they go through the same interview training they inevitably drift in goals and interpretation of what the guidelines mean over the years. What your interview experience is going to be like depends on the particular people interviewing you.

By all means write a blog post telling what you yourself is like as an interviewer at google. But if you want to say something broader really ask yourself, what's your evidence that you understand how other people at google, on other teams and in other offices, do it.

plesner··on Bitcoin emissions alone could push global warming above 2°C [pdf]
Can you expand on this? What makes you sure these predictions won't come true?
plesner··on What Did Ada Lovelace’s Program Actually Do?
Babbage's notes describe what we would call branch-if-zero and branch-if-negative instructions which you could use to implement repetition. Control flow was the least well developed part of the instruction set though, presumably because it would be trivial to implement compared to the arithmetic operations so it could wait.

If you're interested in that kind of thing I wrote a description of the entire instruction set a while back: http://h14s.p5r.org/2012/11/punched-cards.html.

plesner··on Domino-effect of climate events could move Earth into a ‘hothouse’ state
Will agriculture go on easily though? If you look at just two effects, increased variability of the weather and loss of arable land because of rising sea levels, how do those alone not lead to lower output and greater insecurity?
plesner··on Uber Now Tracks Passengers’ Locations Even After They’re Dropped Off
I've seen first-hand uber employees doing things on behalf of the company that are even more unethical than what's being reported in the press.
plesner··on Uber's billion-dollar losses expose the fragile state of the on-demand economy
Isn't that basically what you'd expect with a progressive tax system? Paying taxes is not the only way to contribute to society -- almost all the money people earn do to some extent, through taxes, and consumption, and investments, etc. Which contributes more I don't know. That's why I was hoping for a citation.

To your second point, there is evidence that CEO performance is negatively related to their pay: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1572085. Measuring competence is difficult, wealth is a appealing proxy but maybe not that reliable.

plesner··on Uber's billion-dollar losses expose the fragile state of the on-demand economy
[citation needed]
plesner··on Blind Apple engineer is transforming the tech world at only 22
The original comment said it was their fiduciary duty to minimize taxes. It's not - exploiting loopholes is a choice, not a legal obligation.

You're talking about incentives which is a different discussion. There are incentives that go the other way too: evading taxes looks bad, it's bad for business if society crumbles for lack of revenue, morally it's wrong to benefit from infrastructure, education, etc and not contribute back. But that's not the point I was addressing.

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