egg|nomz|egg changed the topic of #kspacademia to: https://gist.github.com/pdn4kd/164b9b85435d87afbec0c3a7e69d3e6d | Dogs are cats. Spiders are cat interferometers. | Космизм сегодня! | Document well, for tomorrow you may get mauled by a ネコバス. | <UmbralRaptor> egg|nomz|egg: generally if your eyes are dewing over, that's not the weather. | <ferram4> I shall beat my problems to death with an engineer.
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<egg|zzz|egg> !wpn whitequark
* Qboid gives whitequark a first/follow tea
<egg|zzz|egg> !pet whitequark
* Qboid pets whitequark
<egg|zzz|egg> !choose sleep|df
<Qboid> egg|zzz|egg: Your options are: sleep, df. My choice: sleep
<egg|zzz|egg> ;choose sleep|df
<kmath> egg|zzz|egg: sleep
* egg|zzz|egg zzz
<egg|zzz|egg> !wpn bofh
* Qboid gives bofh an ISO 9899 kukri
<egg|zzz|egg> !wpn the котяchrome kitten
* Qboid gives the котяchrome kitten a plasma scale
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<bofh> https://doi.org/10.1093/jac/dky164 WELL THAT AIN'T TERRIFYING AT ALL ("Emergence of an XDR and carbapenemase-producing hypervirulent Klebsiella pneumoniae strain in Taiwan")
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<UmbralRaptor> Fun.
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<kmath> <tanakaiga> 探査機ベネラと金星の妖精 https://t.co/4rJeD3zzny
<bofh> I just got into an argument IRL with someone over why Gandalf was able to cure Theoden's malady but not Denethor's, for like an hour.
<bofh> been awhile since I've gotten this pedantic over Tolkien
<whitequark> lol bofh
<kmath> <✔stuartcantrill> Today has been brought to you by the letter 'C'. C for clusterfuck.
<UmbralRaptor> egg|zzz|egg: Random TRAPPIST-1 observation: getting to the nearest neighbors of the habitable ones (or really any) isn't much higher ΔV than getting from 🜨 to ♂.
<UmbralRaptor> Though more widely separated ones can get, uh, interesting.
* UmbralRaptor assumes that these numbers are correct.
<UmbralRaptor> Also, they have tiny SOIs (4-20x the planet's radius).
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<UmbralRaptor> !acr -add:TNTC Too Numerous To Count
<Qboid> UmbralRaptor: I added the explanation for this acronym.
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<egg|zzz|egg> UmbralRaptor: yeah, Дv is pretty big, you'd need RealSolarSystem to play there decently
<egg|zzz|egg> um, that should be a Δ
<egg|zzz|egg> UmbralRaptor: iirc there was a similar thing when we considered dreary kerbin with regex
<egg|zzz|egg> UmbralRaptor: (that was same diametres as in stock KSP, realistic densities)
<egg|zzz|egg> !wpn whitequark
* Qboid gives whitequark a dye range
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<egg|zzz|egg> bofh: okay but what language was the argument in
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* egg|zzz|egg stares at https://twitter.com/moonreminder
<egg|zzz|egg> it tweets halfway between principia releases :-p
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<egg|zzz|egg> bofh: okay but how do you do simulated annealing on orbital elements to match transit timings anyway
<egg|zzz|egg> bofh: what is your distribution for perturbing the system
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<bofh> egg|zzz|egg: hrmmm. that's actually a damn good question, I was expecting it to be easy to acquire from the МCMC ensemble means but I don't think so anymore.
<egg|zzz|egg> bofh: I don't know how MCMC works at all anyway >_>
<egg|zzz|egg> halp
<egg|zzz|egg> i cannot into optimization
<egg|zzz|egg> !u М
<Qboid> U+041C CYRILLIC CAPITAL LETTER EM (М)
<egg|zzz|egg> Nice
<egg|zzz|egg> bofh: meanwhile phl is trying some genetic algorithm weirdness https://github.com/pleroy/Principia/blob/Trappist2/astronomy/trappist_dynamics_test.cpp#L514-L523
<egg|zzz|egg> (and honestly I'm not sure how to properly do mutations on orbital elements either)
<egg|zzz|egg> !wpn whitequark
* Qboid gives whitequark a bit-addressable iridescent metal
* egg|zzz|egg pokes UmbralRaptor
<egg|zzz|egg> UmbralRaptor: do you know how to do TTV analysis by МCMC
<egg|zzz|egg> "The MCMC analyses of each multi-planet system are carried out using the EMCEE package’s
<egg|zzz|egg> (Foreman-Mackey et al. 2012) ensemble sampler. The EMCEE package employs the algorithm of Goodman & Weare
<egg|zzz|egg> (2010) to evolve an ensemble of ‘walkers’ in parameter space, with each walker yielding a separate Markov chain of
<egg|zzz|egg> samples from the posterior distribution"
<egg|zzz|egg> meep
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* UmbralRaptor does not. =S
<kmath> <8minutesold> Stay tuned for my newest arXiv preprint. https://t.co/Rigt7VrVJL
<UmbralRaptor> !choose poster|poster
<Qboid> UmbralRaptor: Your options are: poster, poster. My choice: poster
<egg|zzz|egg> bofh: nice video on crystals though ^
<egg|zzz|egg> !wpn bofh
* Qboid gives bofh a meow
<egg|zzz|egg> is Qboid a cat
* bofh meows back at Qboid
* UmbralRaptor mrows at Qboid.
<UmbralRaptor> "In the event that Fairfax County Government Offices close due to inclement weather, absentee voting will be cancelled."
<UmbralRaptor> uh
<B787_300> UmbralRaptor: ... how does the office being closed affect absentee ballots?
<UmbralRaptor> B787_300: additional checking suggests that what they're calling absentee is actually early voting. So closed office means no in-person early voting that day.
* egg|zzz|egg meows at UmbralRaptor
<B787_300> Ah. That isn't absentee ballots tho
<B787_300> Also you see that some politicians are complaining about FBs new political ad rules because they didn't follow the instructions that were sent out a month ago?
* UmbralRaptor nyas at egg|zzz|egg.
<UmbralRaptor> I have not.
<B787_300> Which of course the verge posted the article with the title Facebook blocks legitimate candidates from buying ads
<B787_300> Which while technically true is very misleading
<egg|zzz|egg> !wpn UmbralRaptor
* Qboid gives UmbralRaptor a tantalum Сюняев-Зельдович walnut
<egg|zzz|egg> !wpn bofh
* Qboid gives bofh a clopen polenta
* UmbralRaptor points a radio telescope at the walnut.
<iximeow> !wpn walnut
* Qboid gives walnut an alternating state-of-the-art bolometer
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<egg|zzz|egg> bofh: UmbralRaptor: if I have transit times with errors on the transit times, what should I optimize for?
<egg|zzz|egg> bofh: UmbralRaptor: is there some sort of fancy likelyhood thing
* egg|zzz|egg bad at statistics
* UmbralRaptor is okay at frequentist. Bayesian still looks like computational demonology.
<UmbralRaptor> There's probably some sort of "maximum likelyhood estimator", but I'm not sure what it looks like.
<egg|zzz|egg> I don't know but I know that it's called "Maximum-Likelihood" in german too
<egg|zzz|egg> (whereas it's Maximum de vraisemblance in french because we like translating things)
<bofh> sec, doing groceries (was distracted by open bluetooth media links, I'm Han Solo got blared in places).
<UmbralRaptor> !wpn -add:wpn computer
<Qboid> UmbralRaptor: Weapon added!
<UmbralRaptor> !wpn -add:wpn ordinateur
<Qboid> UmbralRaptor: Weapon added!
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<egg|zzz|egg> !wpn bofh's groceries
* Qboid gives bofh's groceries a phased theatre
<egg|zzz|egg> !wpn UmbralRaptop
* Qboid gives UmbralRaptop a magnesium railgun-like page table
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<egg|zzz|egg> whitequark: котяpics?
<egg|zzz|egg> !wpn whitequark
* Qboid gives whitequark an intensional cotter pin
<egg|zzz|egg> ah so it wasn't the chipmunk rouge after all https://twitter.com/stephentyrone/status/1000379565041209346
<kmath> <stephentyrone> Update https://t.co/HfEMC8aswq
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<kmath> <tanakaiga> 探査機ベネラと金星の妖精 https://t.co/4rJeD3zzny
<egg|zzz|egg> !wpn bofh
* Qboid gives bofh a high-voltage cryptocurrency
* egg|zzz|egg pokes bofh in the likelihood
<bofh> I literally just sat back down at a computer, I need to think of what the ensemble statistics are like here for a bit.
<bofh> I'm used to fairly natural systems where you just have a Hamiltonian, but I don't think one for TRAPPIST-1 would be linear since it's classical
* bofh takes the boundary of the polenta
* egg|zzz|egg eats the interior
<egg|zzz|egg> bofh: up to now we're just using that genetic algorithm to minimize the sum of squares of residuals on transit timings, with no regard to the error bars on the transit timng observations
<egg|zzz|egg> bofh: and the L2 norm being the L2 norm, we end up with 5 min but a max transit timing residual of 2 h or something similarly daft
<bofh> Like I feel like L^∞ is the norm you want here
<bofh> Mind you, optimizing wrt. L^∞-norm is nasty, particularly when your problem doesn't have differential structure (OTOH, it feels like something like this *should* have enough for at least a Jacobian to be sensible, perhaps even a Hessian).
<egg|zzz|egg> bofh: well, I'm not sure the uniform norm is appropriate since the observations actually have errors
<egg|zzz|egg> so you'd have to take into account the error bars somehow
<bofh> oh *yuck*
<egg|zzz|egg> bofh: it's astronomy, not numerics :-p
<egg|zzz|egg> bofh: maybe the probability that the transits on the computed transits fall into independent normal distributions corresponding to the observations?
<egg|zzz|egg> is that how likelihoods work
<egg|zzz|egg> am I going to summon bayesian demons
<kmath> <slava_pestov> @stephentyrone Cats
<egg|zzz|egg> bofh: does minimizing the P-value assuming independent normal distributions around the observed values make sense?
<bofh> you probably want to optimize log likelyhoods on the normal distributions
<bofh> I don't think directly minimizing p-values makes any sense here, statistically, but it should still produce reasonable data.
<egg|zzz|egg> bofh: how does optimizing log likelihoods work though, I'm not looking for a distribution?
<egg|zzz|egg> bofh: okay I managed to underflow things with my probabilities :-p
<bofh> um
<bofh> how? :P
<egg|zzz|egg> bofh: so I'm trying things out, just using a 0.001 day blanket σ for now (data entry is not fun), and I get residuals to the tune of thousands of seconds on the initial guess, which is rather unlikely; multiply that by itself over the number of transits and it gets silly
<bofh> Yeaaaaaaaaaaaaah that's going to be dynamically unstable
<egg|zzz|egg> bofh: that's going to be 0, mostly :-p
<egg|zzz|egg> bofh: is there a way to compute log erfc
<egg|zzz|egg> has something gone horribly wrong if i'm trying to compute log erfc,
<bofh> Not really? Done that before.
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<egg|zzz|egg> bofh: okay but how do i do it
<egg|zzz|egg> bofh: if this turns into spending another month writing an elementary function with exactly one usage I'll be slightly annoyed :-p
<bofh> log(erfc(x)), both are standard functions in libm and the result *is* numerically stable
<egg|zzz|egg> bofh: erfc underflows quickly though?
<bofh> yeah, ideally you have erfc(x) = e^{-x*x}*erfcx(x), and the log of that winds up being log(erfcx(x)) - x*x, and erfcx(x) can be nicely implemented via Padé approximants (boost::math does this, you can just pull the P and Q polys out of the header and then feed them to Estrin). alternatively, you can use erfc(x) = 1-erf(x), erf(-x) = -erf(x), so erfc(-x) = 1-erf(-x) = 1+erf(x), so you compute
<bofh> log1p(erf(-x)) if your erf(x) is defined correctly for ...
<bofh> ... negative values (not all impls are).
<bofh> (Yes I know that file path from memory, don't ask >_>)
<egg|zzz|egg> bofh: tbh I can probably get away with log erfc directly
<bofh> You *should*, but you were complaining about underflow so I numerical analysis'd! :P
<egg|zzz|egg> :D
<bofh> (That reminds me, I need to actually get back to figuring out why those optimal guesses for your n'th root functions scarily well fit a linear relation, with weird oscillations in the values and relative error over the order).
<bofh> (aaaaaaaaaaaaaaaaaaaaaaaaaaa so much to do)
<egg|zzz|egg> bofh: also the Nice 69th root
<egg|zzz|egg> (what are 69th roots for anyway)
<egg|zzz|egg> bofh: also doubledoubledouble errors
* egg|zzz|egg stares
<egg|zzz|egg> lɒl it *does* underflow
<egg|zzz|egg> okay let's try that log1p erf -x
<bofh> right, that too, I meant to look at how to do error analysis for that and then conferences and then paper deadlines+uveitis combo
<bofh> !u lɒl
<Qboid> U+006C LATIN SMALL LETTER L (l)
<Qboid> U+0252 LATIN SMALL LETTER TURNED ALPHA (ɒ)
<Qboid> U+006C LATIN SMALL LETTER L (l)
<bofh> rofl
<bofh> Approval.
<egg|zzz|egg> oh so there's a backstory to that
<egg|zzz|egg> if you look at the banlist you'll see "ian"
<egg|zzz|egg> there was somebody known as ian2
<egg|zzz|egg> who was a general annoyance in #kspmodders back when that was a thing
<egg|zzz|egg> and who terminated sentences by ". lol."
<X> Omg. Lol
<egg|zzz|egg> (not sure about that final full stop actually, might have been ". lol")
<X> I wonder if he is still alive
<egg|zzz|egg> bofh: anyway, at some point majiir (snoozee) got annoyed and bade one of his bots (maybe eye of jeb?) kick anybody who lolterminated a sentence, or maybe simply said lɒl
<egg|zzz|egg> bofh: hence the workaround, my client has a macro to turn it to the appropriate IPA :D
<bofh> NICE.
<bofh> Also there's a bot named Eye of Jeb? lmao
<X> O_o you are not the real bofh.
<egg|zzz|egg> bofh: there used to be an Eye_of_Jeb
<egg|zzz|egg> X: wait what
<X> Heresy
<egg|zzz|egg> who is the real bofh then
* egg|zzz|egg is confused
<egg|zzz|egg> am I the real egg
<X> Le google
<X> It is a thing. On the earlier internet.
<X> It involves certain devices.
<X> Some which have strong magnets.
<bofh> I am not Simon Travaglia, no.
<egg|zzz|egg> bofh: Eye_of_Jeb would stare at those who said mechjeb
<bofh> I'm curious why someone *would* say mechjeb.
<egg|zzz|egg> bofh: https://forum.kerbalspaceprogram.com/index.php?/topic/154834-14x-anatid-robotics-mumech-mechjeb-autopilot-273-31-march-2018/ ?
<egg|zzz|egg> bofh: lamont works on doing a fancy guidance module in there, which may interface with principia in the future
<egg|zzz|egg> Atlas-Centaur PEG, but I think he has moved on to much fancier algorithms
<egg|zzz|egg> bofh: wait the log1p thing will underflow just as much, right?
<egg|zzz|egg> since it will be log1p -1
<egg|zzz|egg> (well not underflow, but still be useless)
<bofh> Well no it won't, since there's no subtraction, assuming a numerically stable implementation of erf(x).
<bofh> <shrug>
<bofh> It's worth a quick try.
<egg|zzz|egg> bofh: it won't underflow, it's just that the result of erf will be -1
<egg|zzz|egg> with all other bits being far into the distance
<bofh> Ahh.
<egg|zzz|egg> bofh: okay how do i write a log erfc that's correct to a couple digits, I'm doing a genetic algorithm here, I don't need precision :-p
<egg|zzz|egg> -2/√π (x+x²) :-p
<bofh> I mean if you want more precision, http://csclub.uwaterloo.ca/~pbarfuss/erff.c look at the compute_erfcf path and split out the exponential appropriately, and use a power series or just log(erfc(x)) for the x < 1.5 case.
<bofh> but honestly for a GA -2/√π (x+x²) should actually suffie
<bofh> suffice*