Open thread, 21-27 April 2014

Metus

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Thread started before the end of the last thread to ecourage Monday as first day.

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Thread started before the end of the last thread to ecourage Monday as first day.

Pure curiousity question: What is the general status of UDT vs. TDT among yall serious FAI research people? MIRI's publications seem to exclusively refer to TDT; people here on LW seem to refer pretty much exclusively to UDT in serious discussion, at least since late 2010 or so; I've heard it reported variously that UDT is now standard because TDT is underspecified, and that UDT is just an uninteresting variant of TDT so as to hardly merit its own name. What's the deal? Has either one been fully specified/formalized? Why is there such a discrepancy between MIRI's official work and discussion here in terms of choice of theory?

I'm not serious, but I'd say that there's little actual use of TDT because it requires us to solve the difficult problem of finding the right causal and logical structure of the problem - this can be handwaved in by the user, but doing that feels awkward. Folk-UDT ("just execute the best strategy") is sufficient for most purposes, both in application and in e.g. trying to understand logical uncertainty.

On the other hand, using causal structure is what lets us consider hypotheticals properly - so TDT will not have some issues that typical-UDT does... (read more)

3gsastry12y

Here's one attempt to further formalize the different decision procedures: http://commonsenseatheism.com/wp-content/uploads/2014/04/Hintze-Problem-class-dominance-in-predictive-dilemmas.pdf (H/T linked by Luke)

14Wei Dai12y

Why do you say that? If I do a search for "UDT" or "TDT" on intelligence.org, I seem to get about an equal number of results. [...] This seems accurate to me. I think what has happened is that UDT has attracted a greater "mindshare" on LW, to the extent that it's much easier to get a discussion about UDT going than about TDT. Within MIRI it's probably more equal between the two. [...] As I recall, Eliezer was actually the one who named UDT. (Here's the comment where he called it "updateless", which everyone else then picked up. In my original post I never gave it a name but just referred to "this decision theory".) [...] There has been a number of attempts to formalize UDT, which you can find by searching for variations on "formal UDT" on LW. I'm not aware of a similar attempt to formalize TDT, although this paper gives some hints about how it might be done. It's not really possible to "fully" specify either one at this time because both need to interface with a to-be-discovered solution to the problem of logical uncertainty, and at this point we don't even know the type signature of such a solution. In the attempts to formalize UDT, people either make a guess as to what the type signature is, or side-step the problem by assuming that all relevant logical facts can be deduced by the agent.