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robinhouston

12,368 karma · joined June 3, 2009

Mathstodon: @robinhouston

Cofounded https://flourish.studio; now exited & looking for the next big project

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robinhouston··on Long division verified via Hoare logic
Interesting to hear your experience. I was there 94–97, when the curriculum was still pretty heavy on formal methods (and functional programming).

For me it was wonderful. I already knew how to write computer programs, as that's what I had spent most of my waking hours doing before that point, but learning how to think rigorously about the correctness of programs was a revelation to me.

robinhouston··on Tom Stevenson on the deciphering of Linear Elamite
It simply means that the symbols are composed of lines – as opposed to a system such as cuneiform.

See https://en.wikipedia.org/wiki/Writing_system#Linearity for more detail.

robinhouston··on Simulating Time in Square-Root Space
This cool result relies on an amazing algorithm that was discovered last year: the Cook-Mertz tree evaluation procedure.

See [0] for an exposition, or [1] for a recent popular article about it.

0. https://www.wisdom.weizmann.ac.il/~oded/p_TreeEval.html

1. https://www.quantamagazine.org/catalytic-computing-taps-the-...

robinhouston··on Elon Musk and Spiky Intelligence
Damn. I thought this was an interesting discussion of the multifactorial nature of intelligence, with reference to a topical example; but the comments so far make me think it's going to be challenging for us to have a normal conversation on a topic that involves such a divisive character.
robinhouston··on Apple pulls data protection tool after UK government security row
The Bloomberg article has a little more detail about this:

> Customers already using Advanced Data Protection, or ADP, will need to manually disable it during an unspecified grace period to keep their iCloud accounts. The company said it will issue additional guidance in the future to affected users and that it does not have the ability to automatically disable it on their behalf.

robinhouston··on Chimes at Midnight (2024)
The title is referencing a ’60s movie, I think. Nothing particular is happening at midnight, as far as I know.
robinhouston··on Chimes at Midnight (2024)
I am amused by the way the author gives such detailed directions for “an enterprising trespasser” to pay an unauthorised visit to the Clock.

It’s also a clever device to make the account of the author’s visit more vivid, because I as the reader imagine making the journey myself.

(But I do think it would be a fun adventure to try to follow the directions.)

robinhouston··on Optimality of Gerver's Sofa
An interesting thing about this proof is that it looks as though an earlier draft relied on computer assistance – see the author’s code repository at https://github.com/jcpaik/sofa-designer – whereas this preprint contains a proof that “does not require computer assistance, except for numerical computations that can be done on a scientific calculator.”
robinhouston··on Optimality of Gerver's Sofa
The downloadable extras at the bottom of https://www.math.ucdavis.edu/~romik/movingsofa/ may be useful – especially the Mathematica package, if you have Mathematica.
robinhouston··on An Aperiodic Monotile (2023)
I don't know whether anyone's designed a spectre soccer ball, but someone has designed a soccer ball based on the hat tile.

https://youtube.com/shorts/_Rruxxrz9nY

robinhouston··on How Did You Do on the AI Art Turing Test?
The funniest result of this experiment is the discovery that most of the participants who thought they hated AI art actually liked it:

> The 1278 people who said they utterly loathed AI art (score of 1 on a 1-5 Likert scale) still preferred AI paintings to humans when they didn't know which were which

There’s also a good joke at the end:

> Marcel Duchamp famously tried to put a urinal in an art museum to challenge people’s view of what art was. The administration rejected it, but Duchamp had the last laugh: in 2004, a survey of art professionals judged it the most influential artwork of the 20th century. Art, it seems, is most meaningful when it challenges our very concept of what art is.

> By this standard, I submit that Sam Altman is the greatest artist of the 21st century.

robinhouston··on The letter ℘: name and origin? (2017)
I think the answer by teika kazura on the linked page explains pretty thoroughly why this is not “good enough”. Most importantly:

> In Unicode the letter ℘ is given the codepoint U+2118 in the block "letterlike symbols", named "script capital p". But in fact it's lowercase.

Unicode technical note https://www.unicode.org/notes/tn27/ clarifies:

> Should have been called calligraphic small p or Weierstrass elliptic function symbol, which is what it is used for. It is not a capital "P" at all. A formal name alias correcting this to WEIERSTRASS ELLIPTIC FUNCTION has been defined.

robinhouston··on Interview with gwern
It's been a bumper week for interesting podcast interviews with an AI theme!

In addition to this, there are Lex Fridman's series of interviews with various key people from Anthropic [0], and a long discussion between Stephen Wolfram and Eliezer Yudkowsky on the theme of AI risk [1].

0. https://youtu.be/ugvHCXCOmm4

1. https://youtu.be/xjH2B_sE_RQ

robinhouston··on Thoughts on Arc
Ah! Shame, it’s interesting.
robinhouston··on Industrious Dice
I'm (pleasantly) surprised to see this on the front page of HN!

If anyone really wants to nerd out on the rhombic triacontahedral die, my proof of uniqueness is at https://s3.boskent.com/rhombic-triacontahedron-die/uniquenes...

I first discovered the result computationally, using a program written in https://sentient-lang.org/, before finding the ‘human’ proof described in that PDF.

robinhouston··on We need to liberate the Postcode Address File
Thanks for the clarification. I’d forgotten that ernestmarples only offered postcode-to-location lookup: it was a long time ago.

I suppose this is encouraging! It shows that the forces of openness are gaining ground in this battle.

robinhouston··on We need to liberate the Postcode Address File
This is a long-running battle. Those with long memories may remember the skirmish 15 years ago, when a small group of developer-activists set up a website that allowed free access to postcode data (ernestmarples.com, named after the inventor of the modern British postcode system).

Needless to say, it was rapidly shut down following threats of legal action by Royal Mail.

https://www.theguardian.com/technology/2009/oct/05/ernest-ma...

https://blog.okfn.org/2009/10/05/ernest-marples-uk-postcode-...

robinhouston··on The anatomy of a 2AM mental breakdown
As others have mentioned, the bug that led to this late-night stress was a one-line change to the PostHog library[0].

I take this as a reminder of the importance of giving precise names to variables. The code

    res = await originalFetch(url, init)
looks harmless enough. But in fact the `url` parameter is not necessarily a URL, as the TypeScript declaration makes clear:

    url: URL | RequestInfo
The problem arises in the case where it is not a URL, but a RequestInfo object, which has been “used up” by the construction of the Request object earlier in the function implementation and cannot be used again here.

It would have been more difficult to overlook the problem with this change if the parameter were named something more precise such as `urlOrRequestInfo`.

(A much more speculative idea is the thought that it is possible to formalise the idea of a value being “used up” using linear types, derived from linear logic, so conceivably a suitable type system could prevent this class of bug.)

[0] https://github.com/PostHog/posthog-js/pull/1351/commits/2497...

robinhouston··on AI solves International Math Olympiad problems at silver medal level
Some more context is provided by Tim Gowers on Twitter [1].

Since I think you need an account to read threads now, here's a transcript:

Google DeepMind have produced a program that in a certain sense has achieved a silver-medal peformance at this year's International Mathematical Olympiad.

It did this by solving four of the six problems completely, which got it 28 points out of a possible total of 42. I'm not quite sure, but I think that put it ahead of all but around 60 competitors.

However, that statement needs a bit of qualifying.

The main qualification is that the program needed a lot longer than the human competitors -- for some of the problems over 60 hours -- and of course much faster processing speed than the poor old human brain.

If the human competitors had been allowed that sort of time per problem they would undoubtedly have scored higher.

Nevertheless, (i) this is well beyond what automatic theorem provers could do before, and (ii) these times are likely to come down as efficiency gains are made.

Another qualification is that the problems were manually translated into the proof assistant Lean, and only then did the program get to work. But the essential mathematics was done by the program: just the autoformalization part was done by humans.

As with AlphaGo, the program learnt to do what it did by teaching itself. But for that it needed a big collection of problems to work on. They achieved that in an interesting way: they took a huge database of IMO-type problems and got a large language model to formalize them.

However, LLMs are not able to autoformalize reliably, so they got them to autoformalize each problem many times. Some of the formalizations were correct, but even the incorrect ones were useful as training data, as often they were easier problems.

It's not clear what the implications of this are for mathematical research. Since the method used was very general, there would seem to be no obvious obstacle to adapting it to other mathematical domains, apart perhaps from insufficient data.

So we might be close to having a program that would enable mathematicians to get answers to a wide range of questions, provided those questions weren't too difficult -- the kind of thing one can do in a couple of hours.

That would be massively useful as a research tool, even if it wasn't itself capable of solving open problems.

Are we close to the point where mathematicians are redundant? It's hard to say. I would guess that we're still a breakthrough or two short of that.

It will be interesting to see how the time the program takes scales as the difficulty of the problems it solves increases. If it scales with a similar ratio to that of a human mathematician, then we might have to get worried.

But if the function human time taken --> computer time taken grows a lot faster than linearly, then more AI work will be needed.

The fact that the program takes as long as it does suggests that it hasn't "solved mathematics".

However, what it does is way beyond what a pure brute-force search would be capable of, so there is clearly something interesting going on when it operates. We'll all have to watch this space.

1. https://x.com/wtgowers/status/1816509803407040909?s=46

robinhouston··on My Favorite Algorithm: Linear Time Median Finding (2018)
The trouble with using this convention (which I also like) in Python code is that sooner or later one wants to name a pair of lists 'as' and 'bs', which then causes a syntax error because 'as' is a keyword in Python. There is a similar problem with 'is' and 'js'.
robinhouston··on "Doors" in Solaris: Lightweight RPC Using File Descriptors (1996)
Back in 1998 or so, a colleague and I were tasked with building a system to target adverts to particular users on a website. It obviously needed to run very efficiently, because it would be invoked on every page load and the server hardware of the time was very underpowered by today’s standards.

The Linux server revolution was still a few years away (at least it was for us – perhaps we were behind the curve), so our webservers were all Sun Enterprise machines running Solaris.

We decided to use a server process that had an in-memory representation of the active users, which we would query using doors from a custom Apache module. (I had read about doors and thought they sounded cool, but neither of us had used them before.)

It worked brilliantly and was extremely fast, though in the end it was never used in production because of changing business priorities.

robinhouston··on 3D Gaussian Ray Tracing: Fast Tracing of Particle Scenes
Ah, thank you! That makes sense.
robinhouston··on 3D Gaussian Ray Tracing: Fast Tracing of Particle Scenes
I’m intrigued by the anonymity of the author(s). I’m sure they have reasons for wanting to remain anonymous, but I can’t imagine what they might be.
robinhouston··on Lessons I Wish I Had Been Taught (1996) [pdf]
I said you would enjoy it, not that you would be able to afford to buy it. :-)

I would guess that quite a few HN readers are in the happy position of being able to spend $105 on an interesting book without suffering financial hardship as a result.

robinhouston··on Lessons I Wish I Had Been Taught (1996) [pdf]
If you enjoyed this, I am sure you will enjoy Rota’s funny and charming book _Indiscrete Thoughts_. It includes this essay, together with many others.
robinhouston··on Asppppp: Portals for Your Mouse Cursor
After seeing the enthusiastic reaction to Ball [0] when it was posted here yesterday, I thought people here might enjoy my favourite silly Mac Desktop toy, which allows you to create portals on your screen you can “see through”, and through which your mouse cursor can also pass.

[0] https://github.com/nate-parrott/ball

robinhouston··on 'Equals' has more than one meaning in math
Fortunately functions from the natural numbers are not countable either. This is Cantor's theorem.
robinhouston··on A Rosetta Stone for Mathematics: André Weil's 1940 letter
In this particular case, the proof literally hasn’t been written up yet! The papers are works in progress, only one of which has been even posted as a preprint so far.

But in general it’s reasonably common for a proof to have been written up to the best of the author’s ability, and for it still to be impossible for anyone else to understand it well enough to be confident in its correctness.

Formal logic was no help, for two reasons. First of all the formal logical systems of the early 20th century were really a sort of existence proof, to show that a formal logical system can in principle be defined, and were too unwieldy and verbose for practical use in non-trivial situations. Secondly, it would then become necessary for the reader to check the correctness of a proof in formal logic, which is an even more difficult task than checking a well-written informal proof.

But this is changing: modern formal proof systems are designed with user-friendliness in mind, and produce proofs that can be verified by computer. It’s now starting to happen that formalisation can be used as a way out of the impasse where a proof is too complicated for anyone but the author to understand. I can think of two examples of this: Thomas Hales’s Flyspeck project [1] was the first such case, and required a monumental effort from Hales and his collaborators. Much more recently, Randall Holmes’s proof that NF is consistent was formalised [2], finally putting to rest a very old question in the foundations of logic.

1. https://arxiv.org/abs/1501.02155

2. https://www.logicmatters.net/2024/04/21/nf-really-is-consist...

robinhouston··on A Rosetta Stone for Mathematics: André Weil's 1940 letter
I assume the reason this article has been published this week in particular is that a proof of the geometric Langlands conjecture has just been announced. [1]

The first paper in the series was posted to the arXiv yesterday. [2]

It’s obviously far too soon to say whether the proof is correct, but I’m sure experts will be taking a keen interest.

1. https://people.mpim-bonn.mpg.de/gaitsgde/GLC/ 2. https://arxiv.org/abs/2405.03599

robinhouston··on There’s a 30-year old dead Rabbit in Seven Sisters tube station
They will fail to rhyme in any rhotic accent (e.g. general American, most Scottish accents, etc), where the ‘r’ in pork is pronounced.
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