@etirabys and I have been trying to figure out what to do when you've just made a post, but wish to edit it substantially. The problem here is that someone might have seen it already and be composing a reply, and it'd be a bummer if they wasted effort typing out a reply that your edit renders moot.
Some ideas we had:
If you're reblogging as part of a conversation with someone, ping the person you're conversing with over IM. Of course, some other people you didn't ping might be composing replies!
Copy the post's text, delete the post, and then repost it with your edit. I think this is worse than #1, since it doesn't abort the in-progress reply effort.
I think it's impossible to prevent all effort wastage once you've posted, since posting could immediately kick off a reply.
I came up with the following, unfortunately very busted, algorithm, which I will now spew onto tumblr in an effort to nerdsnipe y'all into devising a better one:
Consider how your post could trigger a reply. Most of the time, it's going to be via the post showing up in the dash of someone who's following you. So,
1. Let S := your set of followers
2. Go through S and message every user in turn that you're about to edit.
3. Once you've done that, reload the post's notes. If there are no reblogs since you last checked the notes, you're done! Post your edit! Otherwise:
4. Someone's reblogged your post. Oh no! Their followers could be replying!
5. For each of the reblogging users you found in #3, download their set of followers.
6. Let S := union of all sets from #5.
7. GOTO #2
This is not guaranteed to terminate, since you're racing the outward wave of causality from your ill-considered post (you're probably hosed if your post goes viral). But, assuming you're fast enough, you're eventually going to halt the damage.
Unfortunately, this doesn't actually work because:
You can't actually enumerate the set of users who might have seen the post. Nonfollowers could see it on "in your orbit", or search, or tag subscriptions, or by navigating to your tumblr URL. This probably isn't fixable, so let's assume your followers are the only users that see your posts.
Someone might see your post between the time you look at your notes in #3 and the time you post your edit.
tumblr might be eventually consistent (or, at any rate, not whatever consistency model is required from tumblr’s externally visible behavior), meaning you can't make any deductions from your dash/notifications about how far your post has not gotten.
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A speculation on the length of proofs of open problems Broad Institute source Nick Patterson is one of the smartest people I have ever known. Today I would like to talk about something he once said...
i like the form of exercises TAOCP uses. TAOCP is a mathematics textbook, and a few of the exercises are stuff you can do just from reading it. But most of them either require some nearly original thinking, literature diving, or in a few cases, actually original thinking. They're rated from 00 to 50, where 00 means do it in your head, 10 means a minute on paper, 20 means several minutes, 30 means "more than two hours' work to solve satisfactorily, or even more if the TV is on", 40 is a school term project, and 50 is an open research problem.
it's supposed to be logarithmic. and honestly, i don't know how good they are as exercises. i've never had a class using TAOCP and i haven't gone through and done most of the problems, since I usually have the TV (computer) on.
but the result of this is that the exercises make some interesting reading. e.g., from a random chapter, an 18 problem is finding the greatest common divisor of 31408 and 2718 and their Bézout coefficients, and a 46 is proving or disproving an open conjecture stated in the text, but not one important enough to have its own wikipedia article.
not many books use this system but when they do it's interesting.
Izhikevich's Dynamical Systems in Neuroscience: The Geometry of Excitability and Bursting is a neat book that has some open problems in the exercises. they aren't labeled as detailedly as TAOCP's, but instead just have "MS" or "PhD" for the kind of project they'd be suitable for.
I find these a lot more interesting than e.g. Wikipedia's list of unsolved problems in neuroscience, which is vague.
the book is very mathematically oriented so this isn't representative of neuroscience as a whole, but hey, what could be.
Chapter 2: Electrophysiology of Neurons
[M.S.] Find the best sequence of step potentials [i.e. for voltage clamp] that can determine activation and inactivation parameters (a) in the shortest time, (b) with the highest precision.
[M.S.] Modify the MATLAB program from exercise 6 [a program to determine activation and inactivation parameters from voltage clamp experiment time series data] to handle multiple currents.
[M.S.] Add a PDE solver to the MATLAB program from exercise 6 to simulate poor space and voltage clamp conditions.
[Ph.D.] Introduce numerical optimization into the dynamic clamp protocol to analyze experimentally in real time the (in)activation parameters of membrane currents.
[Ph.D.] Use new classification of families of channels (Kv3,1, Nav1.2, etc.; see Hille 2001) to determine the kinetics of each subgroup, and provide a complete table similar to those in section 2.3.5 [of the book].
Chapter 5: Conductance-Based Models
[Ph.D.] There are Na+-gated and Cl--gated currents in addition to the Ca2+-gated currents considered in this book. In addition, the Nernst potentials may change as concentrations of ions inside/outside the cell membrane change. This may lead to new minimal models. Classify and study all these models.
Chapter 6: Bifurcations
[M.S.] A leaky integrate-and-fire model has the same asymptotic firing rate (1/ln) as a system near saddle homoclinic orbit bifurcation. Explore the possibility that integrate-and-fire models describe neurons near such a bifurcation.
[M.S.] (Blue sky catastrophe) Prove that (phi' = omega, x' = a+x², and when x = positive infinity, reset x to negative infinity and phi to zero) is the canonical model for blue-sky catastrophe. This model without the reset of phi is canonical for the fold limit cycle on homoclinic torus bifurcation. The model with the reset x = b + sin phi is canonical for the Lukyanov-Shilnikov bifurcation of a fold limit cycle with non-central homoclinics (Shilnikov and Cymbalyuk 2004, Shilnikov et al. 2005). Here, phi is the phase variable on the unit circle and a and b are bifurcation parameters.
[M.S.] Define topological equivalence and the notion of a bifurcation for piecewise continuous flows.
[Ph.D.] Use the definiton in the exercise above to classify codimension-1 bifurcations in piecewise continuous flows.
[M.S.] The bifurcation sequence in Fig. 6.40 [from zero current and up: homoclinic orbit with one stable and one unstable equilibrium inside; homoclinic point loses attractive manifold on outside; homoclinic point becomes unstable node and limit cycle appears; smaller homoclinic orbit appears from homoclinic point surrounding the stable point; this orbit shrinks; the orbit swallows up the stable point and makes it unstable] seems to be typical in two-dimensional neuronal models. Develop the theory of Bogdanov-Takens bifurcation with a global reentrant orbit.
[Ph.D.] Develop an automated dynamic clamp protocol (Sharp et al. 1993) that analyzes bifurcations in neurons in vitro, similar to what AUTO, XPPAUT, and MATCONT do in models.
Chapter 8: Simple Models
[M.S.] Analyze the generalization of [a system earlier in the chapter]: v' = I + v² + evu - u, u' = a(bv-u), and if v = 1 then reset v to c and u to u+d, where e is another parameter.
[M.S.] Analyze [the system related to exponential integrate and fire]: v' = I - v + ke^v - u, u' = a(bv-u), [with the same reset]
[M.S.] Analyze [you get the idea]
[M.S.] Find an analytical solution to the system [that first exercise is a generalization of] with time dependent input I = I(t).
[M.S.] Determine the complete bifurcation diagram of the system [as aforementioned].
Chapter 9: Bursting
[M.S.] Determine the bifurcation diagram of the canonical model for "fold/homoclinic" bursting (v' = I + v² - u, u' = -mu*u, and if v = positive infinity reset v to 1 and u to u+d)
[M.S.] Determine the bifurcation diagram of the canonical models for "circle/circle" bursters [i'm not writing them out]
[Ph.D.] Consider fast-slow bursters of the form (x' = f(x,u), u' = mu*g(x,u), where mu is small and positive) and assume that the fast subsystem is near a bifurcation of high codimension. Treating the bifurcation point as an organizing center for the fast subsystem (Bertram et al. 1995; Izhikevich 2000a; Golubitsky et al. 2001) use unfolding theory to derive canonical models for the remaining fast-slow bursters in [a figure]. Do not assume that the slow subsystem has an autonomous oscillation or that the fast oscillations have small amplitude.
[Ph.D.] Classify all possible mechanisms of emergence of bursting oscillations from resting or spiking.
[Ph.D.] Develop an asymptotic theory of singularly perturbed systems of the [fast-slow form above] that can deal with transitions between equilibria and limit cycle attractors of the fast subsystem.
Chapter 10: Synchronization, which you can read online starting page 148
[M.S.] Derive the phase response curve for an oscillator near saddle homoclinic orbit bifurcation that is valid during the spike downstroke. Take advantage of the observation in Fig. 10.39 that the homoclinic orbit consists of two qualitatively different parts.
[M.S.] Derive the phase response curve for a generic oscillator near fold limit cycle bifurcation (beware of the problems of defining the phase near such a bifurcation).
[M.S.] Simplify the connection function H for coupled relaxation oscillators (Izhikevich 2000b) when the slow nullcline approaches the left knee, as in Fig.10.47. Explore the range of parameters epsilon, mu, and |g(a1)| where the analysis is valid.
[Ph.D.] Use ideas outlined in section 10.4.5 to develop the theory of reduction of weakly coupled bursters to phase models. Do not assume that bursting trajectory is periodic.
Effective altruism is really extraordinarily good at telling people where to give money, and pretty okay at telling people how to create less animal suffering. Guidance on how to do anything else is substantially more opaque.
Effective altruism is really extraordinarily good at telling people where to give money, and pretty okay at telling people how to create less animal suffering. Guidance on how to do anything else is substantially more opaque, because EA discourages a lot of traditional volunteering (at least as a way of improving the world. As a hobby most people are still okay with it). That’s a shame, because there’s a lot left to do.
There are an enormous number of unsolved problems in effective altruism, and philanthropy in general. And there’s actually a fair amount of support for you, if you want to research or attempt a solution. But the support is not very discoverable. A lot of the information spreads via social osmosis, and if you’re more than two degrees out from one of the big EA hubs the process is slow and leaky. It’s not always obvious from the outside how approachable many people and organizations in EA are, or what problems are waiting for solutions. But once you have that knowledge, it’s really hard to remember what it was like when you didn’t, which makes it hard to figure out what to do about the problem.
This is my attempt to address that. Below I have listed info on the major EA organizations, with emphasis on what problems they are interested in, how to learn more about them, and what kind of contact they encourage. I would be surprised if this was enough to enable someone to go from 0-to-implementation on its own, but my hope is that it will provide some scaffolding that speeds up the process of learning the rest of it.
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I have an itch to scratch and I should do something about it. A problem has nagged me in computational biology since my graduate student days and it's contained in the above ancient tutorial.
