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.
<bofh>
I usually just include immintrin.h on the rare occasion I need 'em.
<egg>
context: #1722
<Qboid>
[#1722] title: Implement some operations of R3Element using intrinsics | According to IACA the throughput of these operations goes from 3.00 to 2.00 cycles on Haswell, and this is reflected by a gain of up to 40% on the benchmarks of the polynomials. As expected, the effect is more pronounced for Estrin evaluation.... | https://github.com/mockingbirdnest/principia/issues/1722
<egg>
bofh: so do we need to find a mathematician who was born in the right year for the new year version names from now on :-p
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<bofh>
e1
<bofh>
egg: I concur and agree.
<egg>
that seems tricky
<egg>
bofh: for starters figuring out which sign is Εὐκλείδης's seems hard :-p
<egg>
although if we manage to get to Euler by next year, we have our pig...
<bofh>
Use a different mathematician for that year... also huh, so you do.
<egg>
bofh: well we also want to do mathematicians in alphabetical order of (using some ill-defined collation algorithm)
* UmbralRaptor
🔪 Simbad for putting HTML tags in a TSV file.
<bofh>
Eew.
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<awang>
!u Εὐκλείδης
<Qboid>
U+0395 GREEK CAPITAL LETTER EPSILON (Ε)
<Qboid>
U+1F50 GREEK SMALL LETTER UPSILON WITH PSILI (ὐ)
<Qboid>
U+03BA GREEK SMALL LETTER KAPPA (κ)
<Qboid>
U+03BB GREEK SMALL LETTER LAMDA (λ)
<Qboid>
U+03B5 GREEK SMALL LETTER EPSILON (ε)
<Qboid>
U+03AF GREEK SMALL LETTER IOTA WITH TONOS (ί)
<Qboid>
U+03B4 GREEK SMALL LETTER DELTA (δ)
<Qboid>
U+03B7 GREEK SMALL LETTER ETA (η)
<Qboid>
U+03C2 GREEK SMALL LETTER FINAL SIGMA (ς)
<awang>
egg: pig?
<X>
Quantum physics for a babies is a book and they represent atoms with a Bohr model!
<kmath>
<SpaceGeck> This is what happened when I was doing a content-aware fill to clean up some cosmic rays, but unwittingly had my se… https://t.co/FnI9HDJxhr
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<APlayer>
egg: What can cause an integrator to look fine on the first iteration and spit out total nonsense numbers on the second?
<APlayer>
Do you have tips on how to track this down? Because I am lost in all those formulas
<SnoopJeDi>
it's easier to look at the problem the other way around APlayer and think about what properties of integrators allow any iteration to be not-garbage
<APlayer>
All of them?
<SnoopJeDi>
i.e. what properties of the underlying formulae are you assuming/exploiting that allow you to extrapolate
<APlayer>
There are too many formulae to do this right now
<APlayer>
I am currently walking through every single of them and seeing if they work
<APlayer>
Many don't, BTW
<SnoopJeDi>
well, I'm not saying pick apart every bit of your integrator, if that's what you interpreted it as
<SnoopJeDi>
instead I'm suggesting don't ask "why isn't this working" vs. "why do I expect this to work at all?"
<SnoopJeDi>
the difference can be subtle but the devil's in the details with numerics
<SnoopJeDi>
and you can probably review the source of your method (RKF45 right?) to review what strokes it takes in building its approach
<SnoopJeDi>
APlayer, also, what is your test case? do you have a simple test case that you're validating with (possibly the thing you're asking about?)
<APlayer>
I have a script that is made exclusively to simulate a rocket launch. Three forces acting, engines, aerodynamics and gravity. But the numbers are gibberish
<APlayer>
Terminates with a NaN error because I am performing a square root on a negative number
<APlayer>
Dividing by zero, even, sorry
<APlayer>
But the cause is similar
<SnoopJeDi>
well, if you want to test your *integrator*, ignore all the fluff and test something you can understand. Even a single pendulum can be helpful since the answer is nearly analytic
<SnoopJeDi>
at least, assuming you've written it in a way that allows for that
<APlayer>
I can't just remove all that stuff and code new one for a pendulum
<APlayer>
Those formulae are like half the integrator
<SnoopJeDi>
this is kOS I assume?
<APlayer>
Yes
<SnoopJeDi>
I'm not super familiar but yea I guess there's not a good way to organize things there from what I know
<APlayer>
Well, it's a simple language
<APlayer>
Both, in terms of learning curve and in terms of features
<SnoopJeDi>
anyway, the answer to your original question is "most things" but I'd suspect a non-mathy error the most of all in this context (wrong sign somewhere etc.)
<APlayer>
I guess I'll just have to track some number through this jungle and see where it gets broken
<SnoopJeDi>
yea, "cranking the handle" for a single iteration of your integrator shouldn't be that hard to do by hand to compare against what your integrator is doing
<APlayer>
Ohh, calculations by hand are a nice idea
<APlayer>
Let me make that
<APlayer>
I'll follow the integrator by hand and see where it stops making sense, then
<SnoopJeDi>
LOL this SVG icon provider charges $39.99/yr to be able to select a color for the SVG path from their little color picker.
<SnoopJeDi>
(in their defense, their icons are also CC-BY so it's not like they're preying on *everyone*)
<APlayer>
SnoopJeDi: Notepad++?
<SnoopJeDi>
or Inkscape (or CSS directly in the browser, or...)
<SnoopJeDi>
trying to find a decent SVG of a pint glass for our happy hour shirts (the bar we frequent the most offered to print some for us on their dime)
<APlayer>
CSS support for that is somewhat lacking compared to other properties
<SnoopJeDi>
Found something pretty nice on that site for a starting point, thanks APlayer!
<SnoopJeDi>
!wpn APlayer
* Qboid
gives APlayer a flammable Bloch anticommutator
<APlayer>
!wpn SnoopJeDi
* Qboid
gives SnoopJeDi a pyro flying squirrel
<APlayer>
Woah! I too want flying pyro-squirrels!
<iximeow>
!wpn APlayer
* Qboid
gives APlayer a Hittite tombstone
<iximeow>
i tried
<APlayer>
!wpn iximeow
* Qboid
gives iximeow an ellied pre-warp hydrofluorocarbon
<iximeow>
still stumped at how cool magnetorquers are
<SnoopJeDi>
they are pretty neat
<SnoopJeDi>
and happily people are no longer hostile to the reality that you can't really get great 3-axis stability with *just* those, so CubeSat designs that include reaction wheels are pretty common nowadays AFAICT
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<SnoopJeDi>
oh spectacular, that site already includes the URL and original author in the metadata \o/