2w ago

A young computer scientist and two colleagues show that searches within data structures called hash tables can be much faster than previously deemed possible.

www.quantamagazine.org Undergraduate Upends a 40-Year-Old Data Science Conjecture | Quanta Magazine

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2w ago

A young computer scientist and two colleagues show that searches within data structures called hash tables can be much faster than previously deemed possible.

www.quantamagazine.org /undergraduate-upends-a-40-year-old-data-science-conjecture-20250210/

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The fact that you can achieve a constant average query time, regardless of the hash table’s fullness, was wholly unexpected — even to the authors themselves.
WTF?
I mean first of all, the "article" is just crap IMO, like only hinting att "anazing" things. But also containing basic errors like the above. It's like they don't understand complexity, a constant average time on what? A specific size of a hash table? Or do they mean it scales linearly with its size? Just go through the whole table and voila you have constant time already.
So if they did find something, it's not well explained in the article IMO. Shame, cause those kind of things are interesting, IMO.
Edit: looks like they "cheat" (in a good way) to "reorder" the table to get their results with smarter inserts (their 'elastic hashing') so to not reorder the table. If so, then it's very smart but not groundbreaking. I'm sick and just skimmed the paper, don't kill me.
- "Constant average query time" is not that hard to understand. It means that sometimes access time is e.g. linear, and sometimes you get your content before executing the code. With a hash table large enough and full enough, this can be used to fetch content seconds, minutes, days, potentially years before the program even exists. That's one hell of a breakthrough.
  [edit] /s, oops
  
  ...before the program even exists...?
- They managed to get the time to O(1)
  
  The article is discussing how to reduce the constant time factor which depends on the filling fraction, which is a speed-memory tradeoff when creating the hash table.
  The innovation described allows for the use of fuller tables which are resized less frequently, or faster insertion/retrieval for the existing filling fraction.

This is incredible, but why does the article end by stating that this might not have any immediate applications? Shouldn’t this immediately result in more efficient hash tables in everyday programming languages?
- After reading through the abstract the article is pop sci bunk: They developed a method to save additional space with constant-time overhead.
  Which is certainly novel and nice and all kinds of things but it's just a tool in the toolbox, making things more optimal in theory says little about things being faster in practice because the theoretical cost models never match what real-world machines are actually doing. In algorithm classes we learn to analyse sorting algorithms by number of comparisons, and indeed the minimum necessary is O(n log n), in the real world, it's numbers of cache invalidation that matters: CPUs can compare numbers basically instantly, getting the stuff you want to compare from memory to the CPU is where time is spent. It can very well be faster to make more comparisons if it means you get fewer, or more regular (so that the CPU can predict and pre-fetch), data transfers.
  Consulting my crystal ball, I see this trickling down into at least the minds of people who develop the usual KV stores, database engineers, etc, maybe it'll help maybe it won't those things are already incredibly optimized. Never trust a data structure optimisation you didn't benchmark. Never trust any optimisation you didn't benchmark, actually. Do your benchmarks, you're not smarter than reality. In case it does help, it's going to trickle down into standard implementations of data structures languages ship with.
  EDIT: I was looking an this paper, not this. It's actually disproving a conjecture of Yao, who has a Turing prize, certainly a nice feather to have in your cap. It's also way more into the theoretical weeds than I'm comfortable with. This may have applications, or this may go along the lines of the Karatsuba algorithm: Faster only if your data is astronomically large, for (most) real-world applications the constant overhead out-weighs the asymptotic speedup.
  
  Also never even start optimizing until you profile and are sure the bit you are trying to optimize even matters to the overall performance of your program.
  
  the reason it confused me is because the college student was clearly using the algorithm to accomplish his task, not just theoretically designed. So it didn't seem to be a small improvement that would only be noticeable in certain situations.
  I'm not smart enough to understand the papers so that's why I asked.
- Hash tables are super efficient when they're not nearly full. So the standard trick is just to resize them when they're too close to capacity.
  The new approach is probably only going to be useful in highly memory constrained applications, where resizing isn't an option.
  
  Hash tables are used in literally everything and they always need to minimize resizing because it’s a very expensive operation.
  I suspect this will silently trickle into lots of things once it gets picked up by standard Python and JavaScript platforms, but that will take years.
  
  So... databases? Especially in data centers? Still a nice boost in that case
- Infrastructural APIs are much slower to change, and in a lot of cases the use of those APIs are dependent on a specific version. The change will definitely occur over time as the practical limitations are discovered
- I don't think the speed of hash tables is a problem in most applications except benchmarks.
  
  Hash tables are often used behind the scenes. dicts and sets in python both utilize hash tables internally, for example.
  
  anything that deserializes arbitrary json will put it into a hash table, right? it would definitely speed up the web.
- I haven't read the Tiny Pointers article yet, but the OP article implies that the new hash tables may rely on them. If so, then the blocker could be the introduction (or lack thereof) of tiny pointers in programming languages.
  
  Tiny Pointers was the paper that the student read to get the idea. The paper he co-authored was "Optimal Bounds for Open Addressing Without Reordering"

Hash tables. The backbone of computing, optimized to death by generations of neckbeards convinced they’d squeezed out every drop of efficiency. Then some undergrad casually strolls in, ignores four decades of academic dogma, and yeets Yao’s conjecture into the sun. Turns out you can make insertion times collapse from O(x) to O((\log x)^2)—if you’re naive enough to not know the “rules.”
The real kicker? Non-greedy tables now achieve constant average query times, rendering decades of “optimal” proofs obsolete. Academia’s response? A mix of awe and quiet despair. This is why innovation thrives outside the echo chamber of tenured gatekeepers regurgitating theorems like stale propaganda.
But let’s not pretend this changes anything practical tomorrow. It’s a beautiful math flex—a reminder that theoretical CS isn’t solved, just trapped in peer-reviewed groupthink. Forty years to disprove a conjecture. How many more sacred cows are grazing untouched?
- This is genuinely a beautifully written comment. I'd expect an author with mathematical or physical background to have written it, like Asimov or Pynchon. Bravo!
  
  Thanks for the compliment! For context, I do have an academic background, though no degree. My knowledge in computer science is self-taught, but I’ve built a solid foundation in physics, math (though it’s always humbling), philosophy, and literature. It’s less about formal credentials and more about chasing intellectual rabbit holes.
  Maybe that’s why I’m so allergic to gatekeeping nonsense. Academia’s obsession with rigid frameworks feels like a straitjacket for creativity. The beauty of CS—and science as a whole—is that it thrives on breaking rules, not worshipping them.
  As for Pynchon: he’s a postmodern literary juggernaut. His works are dense, chaotic, and packed with esoteric references—math, history, conspiracy theories. Comparing my comment to his writing? That’s high praise for anyone who thrives in the chaos of ideas.
  Anyway, the real credit goes to those audacious enough to challenge orthodoxy. They’re the ones who remind us that progress isn’t born from conformity but from questioning everything we think we know.
  
  Not weird enough to be Pynchon but it was a good comment nonetheless
- A lot of famous scientists make their breakthroughs at fairly young age, before their mind gets locked into a certain paradigm. Look up Thomas Kuhn's The Structure of Scientific Revolutions, which forwards some interesting ideas on how science is conducted.
  
  The irony of citing Kuhn here isn’t lost on me. His Structure of Scientific Revolutions is practically a manual for how entrenched paradigms suffocate innovation. The young, unjaded minds he describes are precisely the ones who can dismantle decades of "consensus" with a single insight. But let’s not romanticize this—most breakthroughs don’t come from genius alone but from ignorance of the so-called rules.
  That said, the real tragedy is how academia weaponizes peer review to enforce conformity. Paradigm shifts like these aren’t celebrated; they’re tolerated begrudgingly, often posthumously. Yao’s conjecture stood for 40 years not because it was unassailable but because questioning it was career suicide. Imagine how many more revolutions we’d see if the system didn’t punish dissent.

Here's a link to the paper "Tiny Pointers" https://arxiv.org/pdf/2111.12800 those editors at Quantamagazine writes their summary in a strange fashion, for instance using x in stead of n which is normally used in computer science when talking about big O notation.
- This is the paper the article is about: https://arxiv.org/pdf/2501.02305
  
  You are correct it's an confusing article Quantamagazine have written, why do they start highlighting "Tiny Pointers" https://arxiv.org/pdf/2111.12800 when "Optimal Bounds for Open Addressing Without Reordering" https://arxiv.org/pdf/2501.02305 is the main paper, and it disproves part of Tiny Pointers.
- In the article, x is not the size of the hash table, it is the inverse of the table’s filling fraction. A 1000-element table that is 90% full has x=10, N=1000.
  Since they’re not discussing scaling of data sizes, would be confusing to use O(N) notation or people would make that assumption.

Why are these articles even published? They are so incredibly non-technical that it's just impossible to get the point as a reader.
Why even link these articles here? Throw that pop-science in the trash bin, where it belongs.

I don't care about the techno able those group of C's students did.
When will I be able to enjoy faster dicts in my python code?

Very sus. This article is not technically counvincing at all. Probably a few students who dream of inventing the next big thing. Hash tables complexity was mathematically proven to be generally optimal. If you think you optimized it it's because your tests don't reflect the common real world
- The paper was published by IEEE and with professors as co-authors. Only the second author is a student. And I wouldn't dismiss it out of hand like that because of a magazine article. Students come up with breakthroughs all the time. The paper itself says it disproves Yao's conjecture. I personally plan to implement and benchmark this because the results seem so good. It could be another fibonacci heap situation, but maybe not. Hash tables are so widely used, that it might even be worthwhile to make special hardware to use this on servers, if our current computer architecture is only thing that holds back the performance.
  Edit: author sequence

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