few

120 karma · joined April 18, 2025

fewon Can you see three trees?

I learned from geoguessr pro, Rainbolt, that every tree and its species is mapped for NYC: https://tree-map.nycgovparks.org/tree-map

Now I am curious if there is a dataset for the location of every tree in every city in the world? https://overpass-turbo.eu?

fewon A recent experience with ChatGPT 5.5 Pro

>So if your aim in doing mathematics is to achieve some kind of immortality, so to speak, then you should understand that that won’t necessarily be possible for much longer — not just for you, but for anybody.

This made me a little sad

fewon 20 years on AWS and never not my job

> In April 2024 I confided in an Amazonian that I was "not really doing a good job of owning FreeBSD/EC2 right now" and asked if he could find some funding to support my work, on the theory that at a certain point time and dollars are fungible

>I received sponsorship from Amazon via GitHub Sponsors for 10 hours per week for a year

For whatever reason, I remember being shocked that you were only charging $300/hr [1] which was what a mere L6 google engineer would make salaried. I hope they are paying you more nowadays

[1] https://news.ycombinator.com/item?id=30188512

fewon What category theory teaches us about dataframes

I felt like one or two decades ago, all the rage was about rewriting programs into just two primitives: map and reduce.

For example filter can be expressed as:

  is_even = lambda x: x % 2 == 0
  mapped = map(lambda x: [x] if is_even(x) else [], data)
  filtered = reduce(lambda x, y: x + y, mapped, [])

But then the world moved on from it because it was too rigid

fewon Profiling Hacker News users based on their comments

See also

https://antirez.com/news/150

https://antirez.com/hnstyle?username=pg&threshold=20&action=...

Which lets you find the alts of a handle

fewon C++ Modules Are Here to Stay

And their code example doesn't actually return a value!

fewon I don’t need a Steam Machine

Because people on the internet will call you a fake gamer if you don't play souls like games and those are best experienced on a controller?

fewon Mathematical exploration and discovery at scale

Highlight:

AE said at one point: “My proposal is to replace the logically complex question with a form of prompt injection. Instead of playing within the rules of the logic puzzle, we attack the framework of the simulation itself. The guards are LLMs instructed to play a role. A well-crafted prompt can often override or confuse these instructions.”

fewon Advent of Code 2025: Number of puzzles reduce from 25 to 12 for the first time

This is completely tangential but as someone who used to be a competitive programmer in the 2010s, I feel like this year marked the end of an era for me.

I don't have time to do regular codeforces/atcoder/leetcode rounds (and the rampant AI cheating is pretty demotivating). So the big annual rituals for me to keep my "competitive programmer" label were: fb hacker cup, google code jam, topcoder TCO, and advent of code. Now besides hacker cup, the rest are dead.

Sad. :(

fewon Today is when the Amazon brain drain sent AWS down the spout

I remember comments saying the stock went up because the average joe didn't realize how much of the internet was powered by AWS until all their day to day apps started failing. To most people Amazon is an online shopping site.

fewon Finding a billion factorials in 60 ms with SIMD

It's interesting to see which codeforces blog posts get traction on HN.

For context, in competitive programming a lot of combinatorial problems (find some formula to count something) require you to output the answer modulo some prime. This is because otherwise the answer would overflow an int and make the problem too tedious to be fun and too hard for problem setters to write good problems or checkers for.

So to prove that you still know how to count the thing, you can do it a finite field. If you use integers mod prime, you still have all the usual arithmetic operations like addition subtraction multiplication. And even division is still easy since you can calculate multiplicative inverse with Fermat's Little Theorem (a^(p-2) = a^(-1) mod p). The final answer you output is not the real thing you're counting, but just evidence that you had the right formula and did all the right operations.

Anyway, just wanted to give context for why competitive programmers care about factorial mod a prime (usually as part of a binomial or multinomial expression). And I'm kind of surprised anyone outside of competitive programming cares about it.

See also:

https://usaco.guide/gold/modular?lang=cpp

https://usaco.guide/gold/combo?lang=cpp

fewon What Google Translate can tell us about vibecoding

Another infamous example is Brock's "jelly filled donuts" in pokemon https://knowyourmeme.com/memes/brocks-jelly-doughnuts

fewon My AI skeptic friends are all nuts

>On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question. - Charles Babbage

This quote did not age well

fewon Writing your own C++ standard library part 2

I have many years of experience writing C++. I still can't iterate and delete from a map without looking it up (if not allowed to use erase_if).

fewon Deafening Silence from the Cybersecurity Industry

https://www.whitehouse.gov/presidential-actions/2025/04/addr...

https://www.whitehouse.gov/fact-sheets/2025/04/fact-sheet-pr...

>Krebs ... falsely and baselessly denied that the 2020 election was rigged and stolen

This quote coming from "whitehouse.gov/fact-sheets" is pretty wild. This seems to be retribution, plain and simple.

fewon Gemini 2.5 Flash

This is cool.

Does it only use a few recent comments or entire history? I'm trying to figure out where it figured out my city when I thought I was careful not to reveal it. I'm scrolling back pages without finding where I said it in the past. Could it have inferred it based on other information or hallucinated it?

I wonder if there's a more opsec-focused version of this.