UmbralRaptor 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> … one of the other grad students just compared me to nomal O_o | <ferram4> I shall beat my problems to death with an engineer.
<bofh> UmbralRaptor: so like, now I'm curious, what sort of Mars orbit would one land in were you to trip and fall off of Phobos?
<bofh> or would one get Roche'd?
<egg|zzz|egg> bofh: you're not gravitationally bound (well if you are I have questions), so the Roche limit isn't very relevant to you is it?
<bofh> egg|zzz|egg: well presumably you'd be gravitationally bound to Mars in a low-Martian-orbit
<bofh> the question is how stable is it
<egg|zzz|egg> bofh: yes, but the Roche limit is about you being gravitationally bound to yourself
<egg|zzz|egg> and either electromagnetism dominates or, well what are you exactly
<bofh> okay point. I guess you are smaller than, like, Enceladus
<egg|zzz|egg> bofh: so you'd probably end up in an orbit mostly similar to phobos, but the question is whether (and how) you'd interact with Phobos again
<bofh> well I guess that depends on both what your normal to Phobos is and your insertion velocity?
<egg|zzz|egg> bofh: ... you should experiment with RealSolarSystem+Principia :-p
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<bofh> good idea :P
<bofh> sec
<egg|zzz|egg> (Principia is actually fairly inaccurate on phobos's orbit, we'd need all the 2nd order harmonics, not just J2~C20
<egg|zzz|egg> )
<kmath> <scanlime> https://t.co/qC0rkmr87I
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<kmath> <scanlime> These two shy critters will be with me for like a month https://t.co/lmQCh1jUPV
<UmbralRaptor> This was superseded by the Leibniz public diode, yes? https://twitter.com/diodebot/status/894332578416734210
<kmath> <diodebot> Newton proprietary diode
<UmbralRaptor> uh, at the scollback, now I want to know the gravitational binding energy of a human.
<egg|zzz|egg> UmbralRaptor: um
<UmbralRaptor> I know molecular bonds dominate, but still…
<egg|zzz|egg> cat!
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<bofh> UmbralRaptor: LOL @ Leibniz public diode
<bofh> jesus christ the --drg-hsm-error flag to hdparm
<bofh> --drq-hsm-error
<bofh> VERY DANGEROUS, DON'T EVEN THINK ABOUT USING IT. This option causes hdparm to issue an IDENTIFY command to the kernel, but incorrectly marked as a
<bofh> "non-data" command. This results in the drive being left with its DataReQust(DRQ) line "stuck" high. This confuses the kernel drivers, and may crash
<bofh> the system immediately with massive data loss. The option exists to help in testing and fortifying the kernel against similar real-world drive mal‐
<bofh> functions. VERY DANGEROUS, DO NOT USE!!
<bofh> actually the number of hdparm options marked "VERY DANGEROUS DO NOT EVER USE" is kinda terrifying
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<UmbralRaptor> meep
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<UmbralRaptor> !wa 6.674e-11*16/15*pi^2*999^2
<Qboid> UmbralRaptor: 6.674×10^(-11)×16/15 π^2×999^2: 0.000701206…
<UmbralRaptor> Assuming a human is a sphere of water 1 meter in radius, a bit over 700 ergs.
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<UmbralRaptor> !wa 4/3*pi*999
<Qboid> UmbralRaptor: 4/3 π×999 = 1332 π
<UmbralRaptor> !wa 4/3*pi*999.0
<Qboid> UmbralRaptor: 4/3 π×999. = 4184.60…
<UmbralRaptor> Probably a bit high, given the non-uniformity of a typical human.
<UmbralRaptor> Also the fact that 4185 kg is more massive than even a spherical cow.
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<Fiora> bofh: i'm not sorry for stealing that for a tweet,
<bofh> Fiora: go ahead! it's a good tweet
<kmath> <feelthefrog> @FioraAeterna hdparm refuses to do --fwdownload unless you also pass "--yes-i-know-what-i-am-doing --please-destroy-my-drive"
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<Fiora> bofh: isn't it amazing
<Qboid> 4d 0h 0m 0s left to event #0: H-2A • Michibiki 3 [at 2017-08-11 07:00:00]. Say '!koundown 0' for details
<bofh> Fiora: this is like an HDD-destroying trainwreck
<bofh> in manpage form
<Fiora> lol
<egg|zzz|egg> o/ bofh, Fiora
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<egg|z|egg> !wpn Fiora & bofh
* Qboid gives Fiora & bofh a lambda photodiode
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<egg|afk|egg> hm, meeting at 11:30, should head out
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<egg|work|egg> moo
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<bofh> !wpn egg
* Qboid gives egg a nitrogen metabotropic multimeter
<kmath> <dril> Thinking about getting very pissed off on the computer today .
<egg|work|egg> !wpn bofh, Fiora, Iskierka, whitequark
* Qboid gives bofh, Fiora, Iskierka, whitequark a stern line
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<egg|work|egg> !wpn regex
* Qboid gives regex a Лидов nib
* UmbralRaptor is perturbed by the nib.
<egg|work|egg> !wpn UmbralRaptor
* Qboid gives UmbralRaptor a sharp diprotodon
<UmbralRaptor> Ow!
<UmbralRaptor> !wpn egg|zzz|egg
* Qboid gives egg|zzz|egg a white histomorphism
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<UmbralRaptor> o_O
<egg|phone|egg> UmbralRaptor : saw a cat this morning but no battery
<kmath> <mcnees> Is this a water spout out on Lake Michigan? https://t.co/5IsFTTGQ4t
<UmbralRaptor> Battery powered cats?
<UmbralRaptor> Ellied: Don't die.
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<egg> stabbity I got disconnected
<egg> !wpn bofh, Ellied, Fiora, UmbralRaptor, et al.
* Qboid gives bofh, Ellied, Fiora, UmbralRaptor, et al. a meccano theory
<UmbralRaptor> !wpn e
* Qboid gives e an autumn Givens telescope with a delta function attachment
<UmbralRaptor> !wpn egg
* Qboid gives egg a Hermitian postorder type
<bofh> is a Givens telescope one you can freely rotate?
<egg> bofh: that's a given
* UmbralRaptor isn't sure who Givens is in this case.
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<egg> !g Givens rotation
<Qboid> egg: https://en.wikipedia.org/wiki/Givens_rotation [Givens rotation - Wikipedia] (13300 results found, took 0.30s)
<egg> UmbralRaptor: ^
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<egg> !wpn ferram4
* Qboid gives ferram4 a surprise Hermite immersion
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<UmbralRaptor> The surprise is that it has a >50% chance of being real.
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<egg|nomz|egg> diapsids!
<UmbralRaptor> Lewd
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<kmath> <QuantaMagazine> ICYMI: A French mathematician has completed the classification of all convex pentagons that tile the plane.… https://t.co/tXIikMVmfg
<egg|nomz|egg> bofh: ^
* UmbralRaptor was half-expecting to see "Robin Leroy" in that article for some reason.
* UmbralRaptor stabs the headers on that site with Firefox's reading mode.
<bofh> oh god, amazing.
<egg|nomz|egg> (via @spun_off)
<lamont> egg: i may need to get J2 out of principia sooner rather than later
<egg|nomz|egg> hmm
<lamont> my 185x185 orbits launched from KSC are off
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<egg> lamont: huh, by how much
<lamont> 182x188 or something on that order
<lamont> not the fake orbit
<lamont> i need to manually rub some J2 on it today and see if that fixes it first, which i think should be reasonably simple
<egg> lamont: yeah that seems like the best solution for now
<egg> !wpn Sarbian
* Qboid gives Sarbian a sonic screwdriver
<egg> !acr -add:adj torx
<Qboid> egg: I added the explanation for this acronym.
<egg> uh
<egg> !wpn -add:adj torx
<Qboid> egg: Adjective added!
<egg> !acr -remove:adj
<Qboid> egg: I removed the explanation for adj
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<egg> bofh: I wonder whether I should TeX some documentation for that trajectory downsampling method or whether the code + comments are clear enough
* egg stares at incoming ネコバス
<bofh> egg: I think the comments are clear but the code is a bit tricky at times, it's worth TeXing up if you have time tho since the technique is solid and interesting in itsself.
<egg> bofh: what do you mean the code is a bit tricky, it just has an irreducible goto into a nested loop :-p
<egg> [ also for those who may have missed this tweet by UmbralRaptor https://twitter.com/Newpa_Hasai/status/776933458287403008 ]
<kmath> <Newpa_Hasai> Document well, for tomorrow you may get mauled by a ネコバス.
<bofh> egg: I guess anyone reading physics arxiv knows enough coding to parse that, so point.
<egg> bofh: eh, I don't think I'd put it on the arxiv anyway, just in the documentation directory
<UmbralRaptor> egg: be careful because catbuses can fly.
<UmbralRaptor> (Also, it's in the /topic!)
<egg> UmbralRaptor: true
<kmath> <FluffSociety> "Foxes are just cat software running on dog hardware." https://t.co/bKgLycMsC7
<Fiora> ah, finally
<Fiora> i was able to tweet a photo of 16 pounds of methyl ethyl ketone peroxide
<Fiora> er, correction, 32.
<Sarbian> egg: I steered a friend toward wasdkeyboards but I could use the picture of the one with the car to deal the finishing blow
<Sarbian> nvm. My memory is broken
<ferram4> egg, I don't suppose you still have access to a ton of papers behind paywalls?
<Fiora> have you tried sci-hub
<Fiora> 99% of the world's papers are on sci-hub
<ferram4> No, because I am a dunce
<egg> ferram4: unfortunately I am no longer at ETHZ, and at work I only have access to a bunch of boring CS journals, but as Fiora says, sci-hub :-)
<bofh> Fiora: that photo is vaguely unsettling every time I look at it
<Fiora> bofh: It's diluted with 40% phtalate so it's okay.
<egg> Sarbian: mine has a galaxy, not a car
<bofh> heh. yeah, that's indeed fine.
<Fiora> though
<Fiora> i'm curious -why- that dilution makes it no longer explode like crazy
<Fiora> like, what makes it suddenly safer
<ferram4> Welp, nope.
<egg> ferram4: what are you looking for?
<ferram4> J. H. Ahlberg. "Truncated Perfect Nozzles in Optimum Nozzle Design", ARS Journal, Vol. 31, No. 5 (1961)
<egg> bofh: I like the term loosey-goosey and I think I'm going to use it whenever I have bad error bounds from now on https://twitter.com/stephentyrone/status/894673980904411136 :-p
<kmath> <stephentyrone> @FioraAeterna @LiaSae @rygorous It's 16 ulps *if fast-math isn't set*. It's much more loosey-goosey under fast-math.
<ferram4> Then again, it could just be the Sci-Hub site breaking down on me, since it seems unwilling to load properly for some reason. *shrug*
<egg> so DOI 10.2514/8.5577
<egg> ferram4: works for me http://sci-hub.cc/10.2514/8.5577
<ferram4> Ah, got it
<egg> with a pretty pic of an LR-115 \o/
<Fiora> you want something more loosey goosey?
<Fiora> look up division error bounds.
<Fiora> <= 2.5 ulp for y in the domain of 2^-126 to 2^126
<Fiora> for x / y.
<egg> Fiora: on what
<Fiora> a curious range, isn't it?
<bofh> egg: LOL same
<Fiora> glsl/metal/directx/etc division
<kmath> <rygorous> @LiaSae @FioraAeterna @stephentyrone Yeah, pow by 220 is one giant round-off error amplifier: as noted elsewhere, (2046/2048)^220 = 0.8981.
* egg likes that Turing quote on "ill-conditioned"
<egg> "The expression 'ill-conditioned' is sometimes used as a term of abuse applicable to equations, but it seems most often to carry a meaning somewhat similar to that defined below."
<egg> https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/qjmam/1/1/10.1093/qjmam/1.1.287/2/1-1-287.pdf?Expires=1502237175&Signature=bx3-LTDGa3-Bi77D9FUN3bN6ZAZ6YcxjZBHQv35DZCHwOpX4i5pvw1zX5ccpQoTwpOQTWVDtViu5VmaK8U1pSOOcYa2gi3gBHhCEDB~HaGOBQajx8OBfeYZ4BtQOomeYYqsPJvBRALcLb0D3TjGGWSM2aw-IHuihWKNmke7o2z5-Mx0KsRg~hfXa2Kll7bFjMahfoEeZsc48g06N0dZBAW0dEA4VAIttZ6HvH2~GJqLst6eofZBiNp8yBueWVrrsXq7d3zK4BQbwkZOCBRKnjUmYV8EVm
<egg> 8sPN5~UOhhGHE1Zp8Kvvg6nUQpvqk4XRWpUfod1yFR3Z8rJrCvXCvCkAQ__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q
<egg> um
<egg> that's a long link
<egg> qjmam.oxfordjournals.org/content/1/1/287.full.pdf+html
<egg> that's a saner link
<egg> Fiora: I'm having a hard time looking it up, so, what's with the weird range?
<Fiora> so
<egg> Fiora: or rather, what horror happens outside
<Fiora> x * y = x * (1 / y), allowed transformation in fast-math GL/et
<Fiora> *etc
<egg> hm
<Fiora> so
<egg> uh
<Fiora> suppose we're doing 2^126 / 2^127.
<egg> denormals only close to 0, not close to infinity?
<Fiora> 1 / 2^127 is a denormal.
<Fiora> flush to zero.
<Fiora> 2^126 * (1 / 2^127) is zero.
<egg> ooh flushing denormals
<Fiora> thus, 2^126 / 2^127 is zero.
<Fiora> infinite ulp error ;-)
<egg> Fiora: hm, yeah
<egg> Fiora: flushing denormals is shitty, but I think that decomposition would do the same even if you didn't flush them? since 2^(-149) would invert to infinity
<Fiora> yes, but 2^-149 doesn't exist in GL.
<egg> Fiora: aha, so at least you don't have to worry about denormal inputs, just normal inputs that catastrophically fail because of the flushing of denormals :-p
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<Fiora> yup. it's an internal issue caused by the fact that normal inputs require denormal intermediates
<egg> Fiora: also, infinite relative error sure, but I thought by definition ULP distances were always bounded?
<Fiora> well, they SHOULD be bounded.
<Fiora> you can encounter similar issues when using newton-raphson (internally) in the computation of things
<egg> Fiora: no I mean bounded as in I thought the distance between 0 and infinity was the number of representable values in between, not the (very obviously infinite) relative error
<Fiora> ex: in our expansion of sqrt(x), for non-fast-math, we do N-R to refine to precise
<Fiora> but if the input is < 2^-63 we have to pre-multiply by 2^32
<Fiora> so that we don't flush denormals to zero inside of N-R
<Fiora> and... yeah probably, to what you said? "infinite ulp" is kinda a casualism
<egg> (tbh I've never counted anything in ULPs in numerics class, only relative errors)
<egg> (and L infinity norm best norm)
<bofh> (pfft, L^2 norm 4lyfe bro)
<kmath> <scanlime> Peace between Tuco and Cloud...? Luna is still mad and hiding under the tub. https://t.co/WfYFyfmkDq
<kmath> <ObservatoryCats> Human is feeling under the weather so I'm sleeping on her. https://t.co/4Ae7cgIqGf
<kmath> <diodebot> Kirchoff egguation-blocking bidirectional diode
<bofh> LOL
<kmath> <bofh453> Ran across this infamous image just now and feel the need to re-post it. https://t.co/85YHU4dM9U
<bofh> egg: unknown
<egg> bofh: clearly a few layers down it's just a wire with vaguely high parasitic capacitance
<bofh> ROFL