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.
<kmath>
<ctrlcreep> You whisper the comfort spell again and again, and it runs sandpaper over your brain, until your ears are full of d… https://t.co/dACOjIuvMF
<kmath>
<capitalweather> U.S. to be coldest region in world relative to normal over next week. Please note rest of world will be much warme… https://t.co/WH0guiFedn
* UmbralRaptor
still isn't used to the Washington Post being a local(ish) paper.
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<APlayer>
egg: Why if in my ODE the f(t, Y) function actually needs no t, but only the state vector? Did I screw something up?
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<egg|anbo|egg>
it's autonomous
<APlayer>
Sorry?
<APlayer>
s/Why/What/
<Qboid>
APlayer meant to say: egg: What if in my ODE the f(t, Y) function actually needs no t, but only the state vector? Did I screw something up?
<egg|anbo|egg>
it's autonomous
<APlayer>
So this is alright? Nor a problem?
<egg|anbo|egg>
autonomous means the RHS doesn't depend on t
<APlayer>
Alright, so I basically can just cut the t part out of the algorithm
<egg|anbo|egg>
lots of things are autonomous, as you already know from reading that pdf about RK methods I linked you a while back
<APlayer>
I'm afraid I only have it in downloaded format and no URL
<egg|anbo|egg>
though the Struwe script also mentions autonomous functions
<APlayer>
Anyway, sorry for not remembering that, I read the paper a whole while ago and it really confused me, so such details may have slipped my mind
<APlayer>
Let me re-read it real quick
<APlayer>
OK, I think I am up to date with this now
<APlayer>
Thanks!
<APlayer>
Whew, now I can simulate reentry peak G and suicide burns properly
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<APlayer>
egg: RK4 may be fast, but apparently it is not fast enough yet
<egg|anbo|egg>
what stepsize are you using and why
<APlayer>
0.5 sec, total simulation time shouldn't exceed 20 sec
<APlayer>
That is 40 steps
<APlayer>
I condensed much of the maths into single liners and evaluated the numbers, so that the amount of operations is minimal
<egg|anbo|egg>
wait is "simulation time" here your budget for computation time or is it the length of time that you're simulating
<APlayer>
I am simulating a suicide burn, and from experience it is no longer than 10 - 15 sec
<egg|anbo|egg>
ok, so the former
<APlayer>
Not really
<egg|anbo|egg>
um I mean the latter
* egg|anbo|egg
tired
<APlayer>
I cut the sim off when the vertical velocity gets positive
<egg|anbo|egg>
okay what's your time budget
<APlayer>
I did not limit it
<egg|anbo|egg>
<APlayer> egg: RK4 may be fast, but apparently it is not fast enough yet <<< what does this mean
<egg|anbo|egg>
if it means something you have a time budget of sorts
<egg|anbo|egg>
what is it
<APlayer>
The one thing I am sure I can optimize is that I don't need 0.5 sec steps, but that means that I will miss when the burn ends
<APlayer>
In that case, my budget is real time steering of a rocket
<egg|anbo|egg>
how do you know whether it is fast enough or not, can you please answer that question
<APlayer>
It locks the steering, calculates for two or so seconds and re-locks it again
<APlayer>
It used to be smooth adjustments and now it misses the target because of this lag
<egg|anbo|egg>
wait what, it takes *seconds* to compute 40 steps with a trivial RHS like that?
<egg|anbo|egg>
you screwed something up
<APlayer>
Nope, the environment is slow
<APlayer>
The numbers are good, the amount of iterations is good too
<APlayer>
The step size is rather fine for the accuracy I need, but, unless you know a workaround, I cannot fix that
<egg|anbo|egg>
no I'm saying 40 steps aren't going to take seconds to compute unless you're unknowingly doing more work than you should at every step
<egg|anbo|egg>
benchmark your stuff and find where you spend time
<egg|anbo|egg>
(now you also don't need 40 steps, because relying on the stepsize to catch events in the integration is bad, interpolate to find the point of collision, but that's a separate question)
<APlayer>
The one possibility was that I have multiple calls to the RK4 function, but apparently I only have two
<APlayer>
Which is one more than I thought, but this alone wouldn't cause problems. I really think it's the language
<APlayer>
Alright, I eliminated the second call, it is about twice as fast
<APlayer>
Still not fast enough
<APlayer>
And what should I interpolate? Because that looks like the next thing that would speed things up greatly
<APlayer>
Ah, I think I understood
<APlayer>
I looks like a linear interpolation would be even enough, then
<APlayer>
Well, I quartered the step size and the time delay is manageable now
<APlayer>
Far from optimal, but I guess this will work
<APlayer>
s/quartered/quadrupled/
<Qboid>
APlayer meant to say: Well, I quadrupled the step size and the time delay is manageable now
<UmbralRaptor>
Also, my landlord requires physical checks, so I have those anyway.
<rqou>
with some US banks, if you use "bill pay" and they can't send it electronically, the bank will automatically print and mail a check to the recipient
<rqou>
usually for free
<rqou>
and yes, it's dumb
<egg|anbo|egg>
whitequark: hey remember that horrifying wiring photo I showed you
<egg|anbo|egg>
I had to look at that again :-p (and I still don't understand what's going on, something seems to erratically get commuted and it's not by the timer)
<egg|anbo|egg>
is that selector (winter-stop-coal-summer)
<egg|anbo|egg>
and yes there's a dead wasp
<whitequark>
is the rightmost wire coupling uh
<whitequark>
the top connection is to a neutral of something and the bottom connection is a bare copper wire that goes to a SCREW?
<egg|anbo|egg>
yeah but I think it's all floating so that's fine~
<whitequark>
jesus fucking christ
<egg|anbo|egg>
"neutral of something" don't trust the colours
<whitequark>
can you find whoever made this and lodge an icepick into their skull
<whitequark>
this is violence in physical form, it is only fair to respond with more violence
<whitequark>
of course it is all wooden too, so that it would burn nicely if there's ever an oxidized contact
<egg|anbo|egg>
um it's going to be hard to resurrect my grandfather for that (or to find however many heater installers collaborated to produce this)
<whitequark>
I would study necromancy, resurrect every heater installer who touched this, collect them together, and then kill them again
<whitequark>
repeat until satisfied
<egg|anbo|egg>
whitequark: you see all those blue-to-red dominoes though? don't trust the colours
<whitequark>
aaaaaaargh
<egg|anbo|egg>
most of the blues are phases
<egg|anbo|egg>
(at least the inputs are ok, red phases and blue neutral at the top (also a floating red input and a black earth)
<whitequark>
...
<egg|anbo|egg>
whitequark: tbh the panel is wooden but it's all brick behind it
<whitequark>
so if I was there I would rip the entire thing out of the wall and do it properly
<egg|anbo|egg>
tbh next time I'm here I'm probably rewiring it sanely (keeping the silly unused switches on the panel because they amuse me, but the inside is mind-numbingly nuts)
<whitequark>
I just spent like $1000 on tools supplies and appliances because I got too fucking tired of not having proper gear for chemistry (glass/reagent storage shelves, exhaust fans...)
<whitequark>
well it's not *quite* proper, it's creatively used stuff from ikea and home improvement chain store
<whitequark>
e.g. the exhaust fan isn't supposed to be used with flammable vapors. but it's an AC induction motor so there's actually no particular reason to not do it, they're just ass-covering...
<whitequark>
I'd actually rather get proper gear but the vendors are a pain in the ass
<whitequark>
they do not desire to be found and then they do not really want to sell you anything
<egg|anbo|egg>
whitequark: ah yes there's a thermostat going down (the white cable housing green and dirty white wires, also a blue now but not visible in the earlier photos) afaict it's getting its phase at the back of the heater, instead of, like, any of the phase dominoes on the panel
<egg|anbo|egg>
whitequark: bare-copper-to-screw connection *is* weird tbh, no idea what that's from (but then there's lots of weird stuff, no idea what winter-stop-coal-summer was for either but it might be contemporary)
<egg|anbo|egg>
ah yes, I was confused by that phase last time too (I had to work it out again, it's just too stupid even by the standards of this panel) https://logs.tmsp.io/kspacademia/2017-06-27#627643;
<egg|anbo|egg>
UmbralRaptor: I feel like there's some goto mount system that uses that
<egg|anbo|egg>
(digital setting circles by Ellied!)
<UmbralRaptor>
Heh
<egg|anbo|egg>
whitequark: fwiw the black earth at the top is odd in a modern setup but consistent with old french conventions so that completely makes sense; blue phases otoh nopenopenope
<egg|anbo|egg>
wait no, the old convention was white or grey, now I'm confused
<egg|anbo|egg>
ah but phase used to be green and neutral used to be red so everything is screwed up anyway :D
<egg|anbo|egg>
hm, no I'm seeing other sources that say red or black for earth pre-1970
<whitequark>
...
<egg|anbo|egg>
whitequark: yeah pre-1970 colours seem to be a fucking mess but red neutrals are a thing :-p
<egg|anbo|egg>
(and green phases)
<whitequark>
this is just to emphasize why you should never touch a wire without poking it with a test device first