3,177 karma · joined July 20, 2018
But anyway, the United States is extremely rich and has essentially no big problems that can be solved by a small amount (say, a few billion) of money. The problems are either so big that it would take trillions to solve (supporting aging population etc), or blocked by something other than money (politics, regulations, etc). The big problems that can be solved just by throwing a few billion at them are solved quite easily by either the government or by private entities like the Gates Foundation.
As a side note:
> any serious attempt at discussion gets bogged down by [...] without taking a single shower in the same span of time.
This is unnecessary and (somewhat ironically) undermines your own point. I would like to see less of this on HN.
People do look, but it's extremely hard. Take a look at how hard the mechanistic interpretability people have to work for even small insights. Neel Nanda[1] has some very nice writeups if you haven't already seen them.
It's because we're secretly afraid that the physicists are smarter than us.
Less facetiously, physicists keep discovering things that lead to new mathematics we would never have dreamed of ourselves, so we have a healthy respect for how insightful they can be.
ChatGPT 4o as of right now just runs python code, which I guess is "Let me get my calculator", see https://chatgpt.com/share/670df313-9f88-8004-a137-22c302f8bf...).
Claude 3.5 just... does the multiplication correctly by independently deciding to go step-by-step (don't see a convenient way to share conversations, but the prompt was just "What is 1682671* 168363?").
> No it doesn't.
There's really no use in continuing this discussion when one party is unable/unwilling to use precise language to discuss marginal effects. Obviously I presume what you mean is that the marginal effect is too small to be relevant, but discussions with people who round that off to "No it doesn't" rarely go anywhere productive.
Has to be smaller in both directions, right? It has to be vertically smaller to allow f to be computable, but horizontally smaller to keep f' large.
> IIUC, a simpler (but more nitpickable) version would be...
Here I think your f as defined is identically zero, and so you don't get f' by differentiating.
> A much simpler version is f'(x) = {-1 if x<0; +1 if x>0; Chaitin's constant if x=0}. f(x) = abs(x).
Similarly, differentiating abs(x) doesn't get you that function.
But I see where you're coming from, and I agree this doesn't tell us anything profound about computability. That said, it is a cute result that differentiable functions are flexible enough to admit this kind of construction, and that's straightforward but not obviously trivial, as your attempts somewhat ironically show. I think Myhill's proof is pretty close to a minimal working example and trying to fix your examples would result in something that looked very similar.
For others: The original paper is short and very readable - https://projecteuclid.org/journalArticle/Download?urlId=10.1...
The intuition seems to be that computability of a function is actually approximability, and derivatives can be large even when the function is very small, by having the large slope confined to a very small area. So by constructing a function f that contains an uncomputable (but recursively enumerable!) set encoded in the derivative by strategically placing little bumps, but having the bumps grow exponentially smaller, Myhill was able to construct a function that was easily approximable but whose derivative wasn't.
The key detail here is that the bumps grow exponentially smaller in the order the uncomputable set appears in its enumeration. This allows Myhill to construct a sequence of computable functions that (uniformly) approximate f to within 2^(-n). If the bumps weren't ordered in this way, we wouldn't know how far down the sequence to go to approximate f to within 2^(-n). The ordering lets us just look at the first n elements of the uncomputable set.
Why doesn't this allow us to approximate the derivative? Because at any x, we don't know how well we have to approximate f in order to approximate f'(x), so we need knowledge of the entire uncomputable set, which we cannot have.