Hacker News: jethkl

New comment by jethkl in "GPT-5.6 used a prompt to close a 30-year gap in convex optimization"

jethkl — Sat, 18 Jul 2026 16:36:01 +0000

I generally agree, though direction, intuition, and domain knowledge are still relevant. Your breadth-first-search framing feels right, but you still need a sense of which paths are worth following, and you need to know when to trust the results.

I’ve been doing more math as a hobby in the past few weeks — working on lesser-known conjectures and exploring proofs of hard theorems — than I could have managed over the previous several years. It’s an exciting time.

New comment by jethkl in "Middle schooler finds coin from Troy in Berlin"

jethkl — Fri, 17 Apr 2026 22:10:22 +0000

> if you tell me someone just stumbles onto and old coin...

I found a bill from the Weimar hyperinflation era. Its face value was several billion (Milliarden). Its only value was as a curiosity.

New comment by jethkl in "The house is a work of art: Frank Lloyd Wright"

jethkl — Sat, 04 Apr 2026 11:46:54 +0000

> I don't think his Usonian concepts have had much impact on society.

The word Usonain has vanished, but the style's influence has not.

> In 2024, I spent $750,000 on a 1200 sqft rancher built in 1962.

The Jacobs First House [1] in Madison, WI was the first Usonian house; it is credited with many features that became common in the mid-century ranches of the 50's and 60's. Stewart Hicks has a good deep dive [2] into Wright's influence on 20th century architecture.

[1] https://en.wikipedia.org/wiki/Herbert_and_Katherine_Jacobs_F...

[2] https://www.youtube.com/watch?v=ZXyiK-zVKsE

New comment by jethkl in "A short introduction to optimal transport and Wasserstein distance (2020)"

jethkl — Sun, 24 Aug 2025 15:05:33 +0000

Wasserstein distance (Earth Mover’s Distance) measures how far apart two distributions are — the ‘work’ needed to reshape one pile of dirt into another. The concept extends to multiple distributions via a linear program, which under mild conditions can be solved with a linear-time greedy algorithm [1]. It’s an active research area with applications in clustering, computing Wasserstein barycenters (averaging distributions), and large-scale machine learning.

[1] https://en.wikipedia.org/wiki/Earth_mover's_distance#More_th...

New comment by jethkl in "Simulating and Visualising the Central Limit Theorem"

jethkl — Fri, 15 Aug 2025 11:56:56 +0000

There is an analogue of the CLT for extreme values. The Fisher–Tippett–Gnedenko theorem is the extreme-values analogue of the CLT: if the properly normalized maximum of an i.i.d. sample converges, it must be Gumbel, Fréchet, or Weibull—unified as the Generalized Extreme Value distribution. Unlike the CLT, whose assumptions (in my experience) rarely hold in practice, this result is extremely general and underpins methods like wavelet thresholding and signal denoising—easy to demonstrate with a quick simulation.

New comment by jethkl in "Kodak says it might have to cease operations [updated]"

jethkl — Thu, 14 Aug 2025 12:11:23 +0000

> Are they financially screwed

I’ll share an anecdote I witnessed in my extended family–it was horrible. When US Air went bankrupt, employees with decades of service, expecting high five-figure to low six-figure annual income, learned they would get roughly $0.20 on the dollar. For many who were entering retirement, the impact was life-changing, and the stress and disruption it caused could well be argued as life-shortening.

PBGC did take over, but that did not solve the problem.

I believe the root cause was mismanagement of the pension, with the bankruptcy merely exposing this. But I wouldn’t be surprised if, at every opportunity during the bankruptcy process, changes were made that eroded the program’s health.

https://www.thestreet.com/investing/stocks/us-airways-pilots...

New comment by jethkl in "Why Wisconsin's county highways are lettered, not numbered (2019)"

jethkl — Sat, 09 Aug 2025 12:39:29 +0000

This is an instance where Conway's Law applies: state and county systems were kept separate so that maintenance and repairs crews wouldn’t accidentally duplicate work. https://en.wikipedia.org/wiki/Conway%27s_law

New comment by jethkl in "If the moon were only 1 pixel: A tediously accurate solar system model (2014)"

jethkl — Fri, 13 Jun 2025 13:11:14 +0000

There are many physical scale models of the solar system around the world, many walkable, some bikeable: https://en.wikipedia.org/wiki/Solar_System_model

I've seen several, Planet Trek in Wisconsin is a good bikeable one with high quality signage. The sun is downtown, the moon is the size of a peach pit, Pluto is ~20 miles away.

New comment by jethkl in "X X^t can be faster"

jethkl — Sat, 17 May 2025 12:48:35 +0000

how helpful was ai for this? The paper is light on details, but it says the agent was used to generate a kind of seed set (rank-1 bilinear products) that were then fed into the subsequent steps. Evidently this idea succeeded. Curious if anyone here has insight into if this is a common technique, how this agent's output would compare to random or a simple heuristic that attempts the same. Also interested to see how the training objective gets defined since the final task is a couple of steps downstream from what the agent generates.

New comment by jethkl in "Whenever: Typed and DST-safe datetimes for Python"

jethkl — Sun, 13 Apr 2025 13:10:13 +0000

My hope is that a lib like this one or similar could rally mindshare and become integrated as the new standard, and adopted by the wider developer community. In near term, it comes down to trade-offs. I see no decision that works for all use cases. Dependencies introduce ticking time bombs, stdlibs should be correct and intuitive, but at least when not they are usually well tested and maintained, but when stdlib don't meet urgent production needs you have to do something.

Link to Tom Scott & Computerphile from 10y ago on tz madness. https://www.youtube.com/watch?v=-5wpm-gesOY

New comment by jethkl in "Opposing arrows of time can theoretically emerge from certain quantum systems"

jethkl — Mon, 17 Feb 2025 02:30:50 +0000

you can reverse the playback, all the physics of billiards bouncing around works equally well in either time direction.

> If the balls start clustered together, they will scatter over time about the box and the replay of their paths has only one plausible time direction.

It is extremely unlikely that all the billiards will, simply by chance at some point in the future, collect together so they are contained within a very small volume. this shows that there is asymmetry in which direction time flows.

New comment by jethkl in "Opposing arrows of time can theoretically emerge from certain quantum systems"

jethkl — Mon, 17 Feb 2025 02:10:56 +0000

Sharing a simple thought experiment that was shared with me years ago that explains (to me at least) why this is an interesting question. Imagine a billiard ball with nonzero velocity bouncing around an enclosed box. When the ball encounters a side of the box, it bounces off elastically. A replay of this ball's path over time is equally plausible if the replay were run forward or reversed. The preceding is also true if one imagines 2 or 3 balls, with the only difference being that the balls may also bounce off each other elastically. Even in this scenario, reversibility of playback holds no matter the configuration of the balls: they could all start clustered or be scattered and the replay would be plausible when played in either time direction. But this is no longer true when the box (now much larger) contains millions of billiard balls. If the balls start clustered together, they will scatter over time about the box and the replay of their paths has only one plausible time direction. This is because it is extremely unlikely that all the billiards will, simply by chance at some point in the future, collect together so they are contained within a very small volume. To summarize, in the "few scenario" we can plausibly reverse time but in the "many scenario", we cannot. The only difference between scenarios is the number of balls in the box, which suggests that time is an emergent property. layer8's answer elsewhere in this thread says the same, but more succinctly.

New comment by jethkl in "The Physics of Butterfly Wings"

jethkl — Sat, 23 Nov 2024 20:12:19 +0000

I thought the article would discuss physics of flight, but it's about physics of iridescence. Cool, but not what I expected. I've seen butterflies fly in a stiff wind. It seems impossible even when you watch it. I was hoping for some insight into that.

New comment by jethkl in "In the US, regenerative farming practices require unlearning past advice"

jethkl — Sat, 26 Oct 2024 13:07:07 +0000

your comment introduced me to the term permaculture, looks interesting. Do you leverage numerical optimization - linear programming or integer programming for example - in your work?

New comment by jethkl in "Scaling up linear programming with PDLP"

jethkl — Sun, 22 Sep 2024 20:45:17 +0000

That's a clarifying response: I've applied (non)convex programming (LP, QP, MIP, etc) to all the above and a few more, all of which i'd classify as classical applications. Less traditional applications -- I'd like to explore these more --- include data envelopment analysis, which provides a framework for assessing the efficiency of processes based on 1 or more input metrics, and several ideas in papers published at NeurIPS and other conferences that integrate LPs into neural networks in various ways, including AUC maximization. I've also worked on first order methods to solve LPs, and while I'd like to continue in that direction, the area is very crowded with very good existing tools, new and emerging tools that are also often good, and very strong teams building on all of the above. One of the biggest challenges that I see in the OR space is that it requires human expertise to leverage the technology.

New comment by jethkl in "Scaling up linear programming with PDLP"

jethkl — Sun, 22 Sep 2024 16:19:09 +0000

LPs (and MIPs) are used for scheduling, planning, and logistics. These are some of the earliest applications of LPs, dating to the 1930's and 1940's, and these applications are still relevant. The wikipedia page has a good overview of the history and utility of linear programming. https://en.wikipedia.org/wiki/Linear_programming

New comment by jethkl in "What happens to latency if service time is cut in half (2022)"

jethkl — Tue, 18 Jun 2024 14:54:04 +0000

Thank you! -- and thank you to the others who shared!

New comment by jethkl in "What happens to latency if service time is cut in half (2022)"

jethkl — Tue, 18 Jun 2024 12:23:58 +0000

> An extremely useful law to remember....

Would you be willing to provide an example where you applied Little's Law?

New comment by jethkl in "Ernest Shackleton's last ship, Quest, discovered off the coast of Canada"

jethkl — Sun, 16 Jun 2024 16:01:25 +0000

Martin Gutmann's recent talk ( https://www.youtube.com/watch?v=b0Z9IpTVfUg ) supports your point. While Shackleton is celebrated for overcoming disaster, Admunsen reached the south pole by avoiding disaster in the first place. Yet despite Admunsen being more effective, he is not celebrated to the same degree (at least in the US) as Shackleton.

New comment by jethkl in "A year of publishing the MDN Blog"

jethkl — Sun, 05 May 2024 14:50:19 +0000

You are missing the joke. The correct line would read:

  isHexadecimal("HADC0FFEE"); // false