F

Florian

florian.github.io · Personal blog · on HN since 2016

Florian writes about algorithms, probabilistic data structures and machine learning, including the XOR trick, count-min sketch and federated learning.

What HN saysHN commenters link his XOR trick post for details and applications, and discuss it alongside other sketch data structures and reservoir sampling.
15HN people shared it
4linked it in comments
15stories submitted
1.0Kstory points
8 months agolast shared
2016people per year2026

Most-shared posts

  1. 1
    That XOR Trick (2020)
    7 people · 394 points · first shared 2021 · 130 comments on HN
  2. 2
  3. 3
  4. 4
    That XOR Trick (2020)
    1 people · 428 points · first shared 2021 · 231 comments on HN
  5. 5
    Federated Learning
    1 people · 89 points · first shared 2018 · 12 comments on HN
  6. 6
    Count-Min Sketch (2019)
    1 people · 44 points · first shared 2022 · 11 comments on HN
  7. 7
    Federated Learning for Firefox
    1 people · 4 points · first shared 2018 · discussion on HN
  8. 8
    LLMs Understand Base64
    1 people · 3 points · first shared 2024 · discussion on HN
  9. 9
    Computing diffs using the longest common subsequence
    1 people · 1 points · first shared 2021 · discussion on HN
  10. 10
    Base64
    1 people · first shared 2026
  11. 11
    Reservoir sampling
    1 people · first shared 2024

What HN people wrote when they linked it

crote · 2026-03-05
No, the real problem is that people keep giving LLMs the ability to take nontrivial actions without explicit human verification - despite bulletproof input sanitization not having been invented yet! Until we do so, every single form of input should be considered hostile. We've already seen LLMs run base64-encoded instructions[0], so even something as trivial as passing a list of commit shorthashes could be dangerous: someone could've encoded instructions in that, after all. And all of that is before considering the possibility of a LLM going "rogue" and hallucinating needing to take actions it wasn't explicitly instructed to. I genuinely can't understand how people even for a second think it is a good idea to give a LLM access to production systems... [0]: https://florian.github.io/base64/
krior · 2025-07-18
https://florian.github.io//xor-trick/ if you want detailed information and a list of possible applications.
krackers · 2024-05-17
Knuth's presentation of this [1] seems very very similar to the heap-version (top-k on a uniform deviate) of reservoir sampling as mentioned in [2]. The difference is in how duplicates are handled. I wouldn't be surprised if this algorithm was in fact already in use somewhere! [1] https://cs.stanford.edu/~knuth/papers/cvm-note.pdf [2] https://florian.github.io/reservoir-sampling/ Edit: Another commenter [3] brought up the BJKST algorithm which seems to be similar procedure except using a suitably "uniform" hash function (pairwise independence) as the deviate instead of a random number. [3] https://news.ycombinator.com/item?id=40389178
kelseyfrog · 2022-07-22
I am enamored by data structures in the sketch/summary/probabilistic family: t-digest[1], q-digest[2], count-min sketch[3], matrix-sketch[4], graph-sketch[5][6], Misra-Gries sketch[7], top-k/spacesaving sketch[8], &c. What I like about them is that they give me a set of engineering tradeoffs that I typically don't have access to: accuracy-speed[9] or accuracy-space. There have been too many times that I've had to say, "I wish I could do this, but it would take too much time/space to compute." Most of these problems still work even if the accuracy is not 100%. And furthermore, many (if not all of these) can tune accuracy to by parameter adjustment anyways. They tend to have favorable combinatorial properties ie: they form monoids or semigroups under merge operations. In short, a property of data structures that gave me the ability to solve problems I couldn't before. I hope they are as useful or intriguing to you as they are to me. 1. https://github.com/tdunning/t-digest 2. https://pdsa.readthedocs.io/en/latest/rank/qdigest.html 3. https://florian.github.io/count-min-sketch/ 4. https://www.cs.yale.edu/homes/el327/papers/simpleMatrixSketching.pdf 5. https://www.juanlopes.net/poly18/poly18-juan-lopes.pdf 6. https://courses.engr.illinois.edu/cs498abd/fa2020/slides/20-lec.pdf 7. https://people.csail.mit.edu/rrw/6.045-2017/encalgs-mg.pdf 8. https://www.sciencedirect.com/science/article/abs/pii/S002002551000397… 9. It may better be described as error-speed and…

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