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12:30 AM
@JohnRennie is liable to know this
12:58 AM
@0celo7 AFAIK, relativistic polytropic solutions aren't used that often for white dwarfs. Certainly not compared to implementations for neutron stars.
1:09 AM
@0celo7 Try something like $\sim10^8\text{ g cm}^{-3}$ for central density. No complaining about units. Also, writing $\gamma$ is pretty much unimportant. Work with $n$ instead.
Out of curiosity, how are you integrating your models? RK4?
2 hours later…
3:06 AM
@HDE226868 Whatever mathematia uses for NDSolve. As I understand it, it selects a method based on what the equation is.
@HDE226868 No complaining about units? I don't even know what cgs is, those units are bad.
I need inch-slug-second.
@0celo7 Can you answer a cosmology question?
3:37 AM
@SirCumference maybe
2 hours later…
5:59 AM
@JohnRennie I need to overclock my CPU
like, badly
my single core performance is not good enough
The trouble is that overclocking is only going to give you a small percentage increase
Maybe 10% at best
Unless you go for crazy measures like liquid nitrogen cooling
@JohnRennie I should have gone for the mofo CPU!
A Ryzen 7?
Is that really that much faster?
6:02 AM
Who knows
but I am getting 100% usage
Which R7 would you go for?
look at this carnage
those 100 spikes are noticeable
I get a ~5 fps drop
I don't need a massive boost
If it was me, I'd live with it for now and upgrade to a Ryzen 7 at some point.
In fact there are rumours of a Ryzen 9 being released ...
@JohnRennie Ryzen 7 has two more cores
it's twice as expensive though :o
How much are those 5 fps worth to you? :-)
6:09 AM
@JohnRennie A few MHz of overclocking, clearly
what good is the water cooler if I don't overclock?
@JohnRennie So, how does one do it?
I have the AMD overclocking tool right here
What do I crank it up to?
There must be overclocking guides out there in Googlespace ...
I've never overclocked a Ryzen so I don't know what would be sensible increments
@JohnRennie People are allegedly overclocking to 4GHz
I'd try 5% steps. For each step run a particularly demanding bit of TW3 and then check the core temperature. As long as the temperatures remain sane and it doesn't crash keep going.
@JohnRennie I wasn't running TW3
Battlefield 1 multiplayer
GPU load was not bad, but the CPU was hit pretty hard
Anything that maxes out the CPUs. You could just use EatCPU.
Though a game would be a better test as it will present a more varied load.
6:22 AM
Good lord
they needed a $140 cooler to get a 4.1GHz clock
does the temperature just explode when you overclock?
@JohnRennie I would probably run a graphics benchmarking program
That's only a 14% increase
It's not exactly transformational ...
Hmm, idk
Maybe it's not worth it
I should go to bed, cheers
@JohnRennie I just don't understand how people are running 144fps rigs
If my CPU is bottlenecking, how do these other people get over twice the performance?
You can roughly double or triple GPU power, but the CPU is basically fixed
The top end Intel CPU has some ridiculous number of cores. 12 cores or somethign like that.
But it's 2000 dollars
6:30 AM
@JohnRennie a sizable portion of the PC communitt runs 144Hz setups
I doubt they all have $5000 to spend on a computer
Seems a little extreme
All the top end i7s are 10 core, so that's double the CPU of your Ryzen.
that reminds me how hopeless one of our first several computational physics assignments was that was over computational QM
If it's CPU limited it's not hard to see how they're doubling the FPS
I had the brilliant idea of doing it all in my 16 GB of RAM with numpy. (I ran out of RAM immediately the first time I tried it)
@JohnRennie my benchmark is 13,000
6:35 AM
iirc we were numerically estimating the energy levels of a harmonic oscillator using an infinite square well basis
and 95% of the assignment was programming code that would run and finish before the due date
@0celo7 well that i9 scores 23,000!
@GPhys Funny, that doesn't seem like the kind of thing that would eat up 16 GB of RAM
@DavidZ You shouldn't underestimate the ability of students to write fantastically inefficient algorithms :-)
^^^ Indeed. This was one of the first assignments, and we were also using our own Python code to do the integrals.
@DavidZ (I just pulled up the question): It was asking how many terms and how wide of square well we needed to correctly determine the first 40 energy levels. It looks like the next question was about a finite square well. (I don't quite remember which part I overran memory on)
@JohnRennie fair point
I guess 40 energy levels isn't exactly trivial anyway
6:51 AM
I recall fairing better than people who didn't code gaussian quadrature or romberg integrators
ha :-P I can imagine that not going well for them
Q: If we bet, that the world is a matrix, is it possible to break ourselves out of it?

user159858I don't enjoy reading physics books any more because I am almost convinced that we are in a computer simulation (I feel like I lost my passion to study physics) I'm not alone in this issue, even tech billionaires are convinced that we live in the matrix. You know, they are billionaires، They have...

I presume that would have been without Numpy?
@DavidZ It was with numpy, but used only as a matrix library essentially
Oh, because I was thinking you can still do numerical integration and get decent performance using vectorized arithmetic
7:01 AM
my simpson's rule for one of the first assignements
(fully vectorized essentially)
Yeah, that's what I meant (I'm assuming f itself is vectorized)
I remember using my romberg integrator for most of the rest of the semester if only because I programmed it with adaptive error
7:18 AM
For my final project in that class I made a high order symplectic integrator and did a Newtonian n-body simulation of ~2000 particles (merging of two 'galaxies')
ooh that sounds fun
@DavidZ final rendering youtube.com/watch?v=Qp0M3gj23YY
code is entirely numpy (used just for vectorization again) and matplotlib
It looks pretty good
@JohnR: Morning :-)
I'm told disc galaxies do actually merge into elliptical galaxies like that, but I didn't put too much effort into the initial conditions of the disc galaxies actually being realistic
7:28 AM
@Kaumudi.H Morning :-)
How was the meeting?
@Kaumudi.H Good, though several of the people who usually attend were away on holiday so it was a bit quieter than usual.
@GPhys It seems to have worked out well enough. Galaxy mergers are definitely a thing, and that looks about right for how they would go down.
Good discussion though. We were discussing The Magic Toyshop by Angela Carter.
@JohnRennie Ah, I see.
7:34 AM
@JohnRennie Right, right, u mentioned her before. Was it good?
I'm not a huge fan of the book. Angela Carter is one of those cult authors whose name is mentioned with reverence, but I find her books hard to read.
Huh. How come?
You need to read her books to understand what I mean.
It's ard to explain her style.
Oh, OK...
She's more interested in characters and the scenery than the plot, so her books contain lots of descriptive text where nothing much happens.
7:36 AM
Huh, I see...
Her boos haha :-)
That's not necessarily a bad thing, but I felt she didn't do a very good job of it in The Magic Toyshop. It felt a bit forced sometimes and also a bit inconsistent.
But if you Google for reviews of the book you'll find lots of people rate it as very good, so I appear to be in a minority.
Ohh, OK, I see...
Anyhow, it's always fun to meet up with friends, so even though I wasn't keen on the book the meeting was still enjoyable.
Right, right :-)
7:40 AM
And I have a curry appointment this afternoon, so the weekend is far from over!
Yes, I remember :-)
Where are u going?
Haven't decided yet, but probably an Indian restaurant in Chester rather improbably named Barton Rouge. I've been there lots of times and it's generally very good.
Improbably named? I don't understand...
Well Baton Rouge is a famous city in the US.
7:43 AM
@DavidZ Indeed! I was quite happy with it
I found it interesting when coding it that even though the 'Force' matrix is skewsymmetric (i.e. $F_{ij}=-F_{ji}$) it was faster to calculate the force twice than to take advantage of this. (Every scheme I could come up with to take advantage of the above relation had a numpy overhead more than the speedup.) I'm sure if I had programmed it in C or the like that wouldn't be true, though.
And I assume Barton Rouge is derived from it's name.
Ah, lol, I see.
But Baton Rouge is famous for the French cuisine, not Indian.
Baton Rouge ( BAT-ən ROOZH; French for "Red Stick", French: Bâton-Rouge [bɑtɔ̃ ʁuʒ]) is the capital of the U.S. state of Louisiana and its second-largest city. It forms the parish seat of East Baton Rouge Parish and is located on the eastern bank of the Mississippi River. As the capital city, Baton Rouge is the political hub for Louisiana, and is the second-largest city in the state after New Orleans, with an estimated population of 228,590 in 2015. The metropolitan area surrounding the city, known as Greater Baton Rouge, is also the second-largest in Louisiana, with a population of 830,480 people...
7:44 AM
Say, do u have pretty canals in Chester?
There is a canal, the Shropshire Union canal.
(I'm looking at their menu now and wow, there seem to very few veg. dishes)
@JohnRennie Shropshire is a little funny sounding :-)
It passes near to my house so I sometimes walk into town along the canal path. It's nice, though I'm not sure I'd say it was beautiful.
Ah, OK...
7:46 AM
@Kaumudi.H It's an English county.
I'm used to it, so I guess it doesn't sound strange to me.
Right :-) I bet Tirunalveli sounds just as funny to you.
Oh, no, I take that back! There are lots of veg. dishes on the menu!
Where the Shropshire Union canal goes through the middle of Chester it passes through a deep cutting that is really spectacular. I don't have any photos though.
> I don't have any photos though
:-( OK.
7:48 AM
It's very narrow with vertical sides that go up for maybe 20 metres.
Oh, wow, I see...
Oh, sheesh, that is beautiful.
Though it doesn't really capture the feeling when you're standing in the canal path.
Of course :-) Kakkanad (a settlement near MEC) is also quite beautiful.
@JohnRennie Wow. You live in a beautiful town!
Chester is nice. I ended up here mostly by accident, but it has turned out to be a nice place to live.
Say, how did you end up there?
My goal is to be able to move to a Norwegian fjord when I retire.
7:54 AM
One second!
When I left university I got a job at a research lab about 20 miles from Chester, and I needed to find a house in the area. I was staying in a hotel in Chester, so I looked in a local estate agent and bought pretty much the first house I saw. I intended it to be just temporary but ... I'm still here :-)
@Kaumudi.H you might wish to check the average temperatures in Norway before you decide to move there :-)
@JohnRennie Ohhh, wow :-)
@JohnRennie Eek, I hadn't thought of that! In any case, I hope to have lived in enough countries by the time I retire to have gotten used to colder temperatures.
@GPhys Huh, that's interesting. I guess that's vectorization. If you can share code that demonstrates that effect I'd be interested to see it (though not now, I'm very busy this weekend).
@Kaumudi.H Lots of people have this notion that it would be great to move out into the countryside when they retire. Well my mother lives in the countryside and it's rubbish.
8:05 AM
@JohnRennie Oh it's not that countryside that people are talking about :-P
From her village there's two buses a day into the nearest town, and a taxi costs about £15 for the round trip.
I would prefer the natural beauty of countryside and the easy availability of stuff in cities to be found in one single place
I know, I know.
@Sid then move to Chester :-)
But still, I hope to be in a state of mind OK with living at a fjord and all.
8:07 AM
@JohnRennie It's that great, is it?
@Kaumudi.H And after you've gazed at the amazing scenery for a couple of days you'll start thinking now what do I do?
@DavidZ No?
Right, right, but I'll think up something to do before I move; I'll work on a book or something!
@JohnRennie Lots of places in Kerala are like that :-)
@JohnRennie Do you see those temperatures? Nothing>20 degrees
I don't think I can survive
There will always be another countryside. If people go to one and find they don't like it, they'll just get wistful about somewhere else.
8:08 AM
And you may tell yourself
This is not my beautiful house!
And you may tell yourself
This is not my beautiful wife!
@Sid celsius? Sounds nice to me (though I didn't think it would be that cold)
@Sid In Chester? At the moment the temperature during the day is around 20 - 25C, which I'd say is about perfect.
We get 15-20 degree Celsius in Winters.
Warm enough to be nice but not so hot that it's uncomfortable to do anything strenuous.
> Perfect
8:10 AM
For us, Warm=30+ but less than 35
The West calls it suffocatingly hot. Which it is not.
More like the north, I would think? E.g. Mexico is "west" and it gets pretty hot too
@JohnR: Going out for lunch!
Will have the usual: fried rice and chilli potatoes.
8:12 AM
same as it ever was :3
@Kaumudi.H anywhere special? i.e. a special restaurant?
@BalarkaSen Hmm?
@Kaumudi.H Talking Heads song.
Ohh, OK.
8:13 AM
I should limit my vocabulary to the large word data collection in James Joyce's Finnegans Wake and various song lyrics.
@JohnRennie Nah, it is a place we've haunted for almost two decades now.
You mean, hunted?
Maybe I will spend 17 years writing a book with that vocabulary
@Sid No, I mean haunted. Visited, I mean.
I should edit that.
8:16 AM
No, I think haunted is a perfectly good word to use.
"haunted" is fine, I got it
I was going to edit that to "It has remained one of our haunts for...".
It's a comic way to say it's a common place of visit for a group of people or an individual
To me, haunted=Scary.
@BalarkaSen Right, right, and this is how I meant for it to read but for a moment, I didn't think haunted would translate as another version of haunts.
8:19 AM
Scary is definitely the most common sense in which it's used, but I do also know it as meaning "frequently visited or occupied", albeit uncommonly used that way. It might come from the idea that ghosts tend to be "attached" to one place. (Or maybe the other way around)
I need to work for a few minutes. Back in a bit ...
Man, I am so hungry! I haven't eaten anything in close to 17 hours :-(
Right, we're here! Toodleoo!
9:37 AM
Wow, it's national ice cream day. Who knew? Not that I need an excuse to eat ice cream :-)
9:59 AM
@JohnRennie Haha wow :-)
I didn't order the usuals after all! I had masala kulcha with paneer butter masala and a fruit salad with ice cream! :-) It was lovely.
masala kulcha - stuffed bread?
Essentially, yes.
Mine were stuffed with spiced mashed potatoes!
My friends have just mailed me with details of the meetup, but we aren't eating until 17:45. That's seven hours from now. I'll be dead of starvation by then.
10:35 AM
@JohnRennie Wtf, so you're really only having an early dinner, not lunch...
(Sorry about the latency; I've just received Rs. 2000 from an aunt for having gotten into MEC!)
@Kaumudi.H Yes, I thought we were meeting up for lunch, but the others are going to see a film and we're eating after the film.
Oh, no :-(
Eat some apples, then, at lunchtime.
I'll survive. I'll be thinner, but still alive :-)
The trouble is that I'm not very good at eating a small snack. Small snacks tend to turn into large meals, then I'll be full and won't want any curry.
The safest option is not to eat at all until the meal.
10:39 AM
Wow, your body is quite mean to you!
3 mins ago, by Kaumudi. H
(Sorry about the latency; I've just received Rs. 2000 from an aunt for having gotten into MEC!)
And now I've got Rs. 5000 in my purse!
I saw. Buy a headphone adaptor!!!
I will but for that, I will ask my mum; I'm saving this lot for later.
@JohnRennie I used to be worryingly thin. So much so that my friends and family used to joke that if I started eating any less than I used to, I'd vanish completely :-)
10:42 AM
I'm thin, but I stopped worrying about it a long time ago :-)
Damn I could quote another line from the same album right now
Sigh, I'm quite tired from having gone out for lunch; how I will survive college I dunno.
@BalarkaSen So why don't you?
"I'm so thin"
10:44 AM
Took my breath away :-P
Well it's a fantastic line
@0celo7 I think I am going to spend the next four days learning from Milnor's red book, chapter 2
At this rate, I'm not going to get through even half a day of classes.
@Kaumudi.H I wouldn't worry about it. I always feel sleepy after eating.
I tend to eat late in the day so I can get everything done before I eat then conk out.
Right, but this isn't exactly about eating alone; I feel more tired than ever if I socialise for a little more than an hour.
Mixed with the eating and all, it's proving to be disastrous, even though I slept for 11.5 hours last night!
10:50 AM
that's easy to fix
Why disastrous? What you describe sounds like fairly typical teenge behaviour to me.
@BalarkaSen Yeah, not socialising is not an option at college.
@JohnRennie It's not fairly typical in my experience.
Disastrous because it drains my sap right away.
It's typical for introverts - you just need to figure what makes you feel energetic again (e.g. reading, exercise)
10:52 AM
@Kaumudi.H I wouldn't be so quick to predict catastrophe. Go to college and take it as it comes.
@ACuriousMind I know, I know. I'm merely predicting that college is going to be a tad exhausting.
If you need to sleep for 11.5 hours then sleep for 11.5 hours.
@Kaumudi.H Life is "a tad exhausting" :P
@JohnRennie Haha, I don't think I'm going to be able to sleep for this long in college; I'm going to try and stick to a 7-hour sleep schedule...
well, the use of the adjective "introvert" is overrated
10:54 AM
@ACuriousMind :-P Right.
@Kaumudi.H Seven hours is not enough sleep for an 18 year old.
At that age you need somewhere in the range 8-10 hours.
:-/ I might not be able to do all of the things if I sleep for that long.
@BalarkaSen Sure. Why do u point this out now?
@Kaumudi.H then prioritise things and omit the low priority ones. Getting too little sleep is not a viable long term strategy.
Hmm, yes, you're right. I will try to figure it out.
10:58 AM
When one claims something is typical for introverts, one is claiming that outside a small subset of exceptions, the mass of people, tagged as "introverts", have that something in question as properties. I'm just pointing out that the suggested mass is vague; it's not clear what or who an introvert is.
For me, the whole introverted/extroverted thing is a relative term - if you stick me at home with a bunch of friends from school and make me interact with them, I'm going to get tired and fed up pretty quickly, but if you stick me in a room with a few of my friends from Uni, that doesn't happen, so how introverted I am depends a lot on who I'm with. Also, 7 hours was a nice, long sleep in undergrad :P
Thereby any adjective imposed upon that given mass is going to be, in turn, vague.
@Kaumudi.H wait and see what the workload is like at college before worrying. I bet it will be a lot lighter than your revision schedule was.
@JohnRennie Are u aware, BTW, that even the number of hours of sleep u get everyday comes with an inherent sense of shame in these parts? At school, some used to scoff at others for sleeping for any more than 6 hours.
@Kaumudi.H some people are arseholes. That's life.
11:00 AM
@Kaumudi.H I would turn round and call them silly and shallow for not having any real interests
I bear no shame for pickling my owls
Though I guess if you nap during the day then your overnight sleep will be shorter ...
No, I don't usually nap during the day because if I accidentally nap for any more than half an hour, I can't get myself to fall asleep at night anytime before 3 AM.
pickling my owls - that's sounds like one of those suspicious euphemisms :-)
But I'm going to risk it and take a quick nap now! @JohnR: Enjoy ur late lunch/early dinner! :-)
11:04 AM
I hope u don't die of starvation by then :-P
I'm doomed ...
Drink water. LOADS of water.
Not many calories in water
That's what I do anyway, when I'm starving and have nothing to eat at home.
@JohnRennie No, but it makes ur brain feel like ur stomach is full for a very short while.
11:07 AM
I generally drink coffee to stave off hunger pangs.
Caffeine is a reasonably effective appetite suppressant.
Coffee then! Copious amounts!
And you get all that exercise running up the stairs to the bathroom :-)
coffeous amount
I'm contemplating buying another PC, so that will give me something to pass the time ...
@JohnRennie Ah, we live on one floor :-) The bathroom is 5 feet away from where I'm currently sitting.
11:09 AM
@JohnRennie Jesus Christ, you're literally the only person who buys computers to pass the time! I wonder if there's someone else like you, but with cars...
@BalarkaSen x'D
@Kaumudi.H If you've got a good aim you could probably reach the toilet from where you are :-)
@Kaumudi.H This one but I won't pay much more than £250 for it and I'm guessing the price will go a lot higher than that.
@JohnRennie Ahem. I'm a girl! Why do people keep forgetting that? My profile picture is that of a girl! ME!
@JohnRennie Wow, £250 is still a lot of money.
It is a very, very powerful PC though. It's considerably more powerful than the laptop I'm using to type this.
11:12 AM
Hmm, I see...
Again, I ask: What on Earth will u do with it?
We'll see. In any case it will almost certainly sell for more than I want to pay.
@JohnRennie The hard drive's a bit small though. Not that that's a hard problem to fix :P
@Mithrandir24601 when I buy computers on eBay I always factor in the cost of replacing the existing disk by an SSD.
In fact this computer has an SSD already, though as you say a small one.
11:16 AM
@JohnRennie Seems like a good idea :) When I got the one I'm using, I somehow managed to get a 500GB SSD drive for an extra £20 (was on offer or something at the time :) )
(and that was on top of the 1TB HDD :P )
The Optiplex 9030 has two drive bays, so I can always put in a large second disk if I need a lot of space, and put the OS and apps on the SSD.
@JohnRennie This is a very good idea. But you obviously know this already :P
@Kaumudi.H I'm not sure I see the point of that freerice web site.
Initially I thought it was some form of crowdsourcing, but I can't see the point of the questions it asks you.
@JohnR: What's ur will going to be like? You've already given laptops and stuff to pretty much everyone you know x'D
@JohnRennie They're too easy, yes, but hey, donating rice!
11:22 AM
The computers I own don't add up to very much because I always buy them cheap on ebay. 0celo7's new gaming machine probably cost more than all my computers combined.
My brother probably spends more on one family holiday than all my computers are worth.
Ah, hmm.
@JohnR: That website has a variety of subjects to choose from, BTW! It even has one for SAT prep.!
No section on Physics though
No :-(
Or you could always pass your time messing with IBM's quantum computer
11:26 AM
Hmm, it appears to be part of the UN food programme.
Hmm. If I have a Riemannian surface $S$ and a vector field $X$ on a chart at $p$ in $S$ that is parallel (that is $\nabla_{\partial/\partial x} X = \nabla_{\partial/\partial y} X = 0$), does that mean $S$ is flat at $p$? In general if I have a Riemannian manifold $M$ of dimension $n$ and $n$ independent parallel vector fields on a chart at $p$, does that mean $M$ is flat at $p$?
(@ACuriousMind Do you know this?)
That number was incorrect; they've actually donated 70,225 Kgs of rice.
@JohnRennie It is, yeah. It's legitimate and all.
11:29 AM
Back to Brazil :^)
@JohnRennie Had to leave the Amplifier for my gf to ship to California
That will be one travelling amp :P
Yes, it's a big heavy lump to be carrying around the world!
Careful though ... you might get charged import duties by US customs.
I know
That would suck
I'm shipping my darned speakers too
What a headache
It would be worth checking with the US customs to see what the situation is. I'm fairly sure you're allowed to bring in your own property without incurring charges.
Hopefully that's the case
and I had to sell my turntable to cover moving costs :(
I'd check before you get the stuff shipped.
11:32 AM
@BernardoMeurer bummer. But to be fair turntables are delicate and the chances of it surviving the shipping weren't that high.
@JohnRennie I had it on the original box though with all the packing
By contrast the amp is built like a tank and could probably survive being thrown across the Atlantic :-)
That thing is like a tank
and weighs 6Kg :P
@ACuriousMind Nevermind, that should be true.
The chart parametrization should be an isometry.
1 hour later…
12:47 PM
$$\odot \smile \odot$$
@JohnRennie For the last week, I have slept for 3-4 hours everyday. Pretty sure, I am sane and doing my everyday chores quite well.
Q: violation of energy conservation in retarded interaction of magnet and coil

Hemal PansuriyaIf i move a magnet towards the coil than magnet will experience resistive force because of the lenz law. This way mechanical energy will convert into electrical energy. But what if magnet and the coil are sufficiently large distance apart. The change in magnetic field travels at the speed of lig...

@BalarkaSen Yes, it is true.
@BalarkaSen Just use the vector fields to compute the Riemann tensor. All of the derivatives vanish. Since the vector fields span the tangent space at each point, all of the component vanish.
2 hours later…
2:40 PM
@0celo7 yeah.... i'm super dumb
2:59 PM
@JohnRennie 3.8 was stable

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