Search found 3683 matches

by PM 2Ring
Wed Jun 15, 2016 7:33 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

Incidentally, you can easily do ceiling division in Python. From http://stackoverflow.com/a/17511341/4014959

Code: Select all

def ceildiv(a, b):
    return -(-a // b)

So -a // b * -b gives the next multiple of b >= a.
by PM 2Ring
Thu Jun 09, 2016 9:46 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1691: "Optimization"
Replies: 53
Views: 10310

Re: 1691: "Optimization"

According to Wikiquote there are two versions of this remark about premature optimization in Knuth's writings. Knuth calls it "Hoare's Dictum", after fellow computer scientist Tony Hoare (inventor of Quicksort, etc), but that's just Knuth having a bit of fun. The real problem is that progr...
by PM 2Ring
Wed Jun 01, 2016 4:16 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1687: "World War III+"
Replies: 34
Views: 8075

Re: 1387: "World War III+"

@sardia

"World War III+" is actually comic #1687; comic #1387 is "Clumsy Foreshadowing".

Whatever happened to the opening post linking the thread to the comic?
by PM 2Ring
Wed Jun 01, 2016 3:58 pm UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1689293

Re: Today I Learned

TIL: When you bleach purple hair, it turns green! I am super fascinated. I Am Not A Chemist, but I suspect that the colour change is due to a change in the oxidation state of a red pigment in the purple dye. On a (possibly) related note: In high school chemistry, I discovered that nitric acid turns...
by PM 2Ring
Mon May 30, 2016 11:29 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1685 : Patch
Replies: 40
Views: 10727

Re: 1685 : Patch

A friend of mine found a python autocomplete that evaluates your code to figure out the autocomplete, so that's kind of like compiling it? I mean I know that Python can't be compiled by definition but that the same concepts, at least. Like the vast majority of modern language implementations, all i...
by PM 2Ring
Mon May 30, 2016 9:36 am UTC
Forum: Coding
Topic: Code duplication vs clarity
Replies: 15
Views: 6997

Re: Code duplication vs clarity

Since it's first and foremost a matter of whether each piece of data is included or not, I would do an alternate version of your first suggestion using binary, like this. case = 0; if (A) case &= 1; if (B) case &= 2; if (C) case &= 4; if (D) case &= 8; if (E) case &= 16; switch ...
by PM 2Ring
Tue May 17, 2016 7:36 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 590
Views: 112274

Re: Miscellaneous language questions

"Bubbler" (with 3 syllables) was the preferred term when I was in primary school, in Sydney, Australia, several decades ago. And they were generally of the unsanitary vertical stream design. In high school, we tended to call the bubblers "the taps"; "bubbler" was a term...
by PM 2Ring
Sun May 15, 2016 5:49 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

Today I discovered the horror of bug dependencies. No, not dependency bugs, those are normal. So there was a bug report for a bug. I couldn't reproduce, but the code looked like the bug should indeed occur. I digged further and discovered three related bugs, which I fixed. Now the bug from the repo...
by PM 2Ring
Fri May 13, 2016 8:53 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1680: "Black Hole"
Replies: 31
Views: 7595

Re: 1680: "Black Hole"

Just how small is this black hole? Assuming that black spot is supposed to be the event horizon then it looks like it has a Schwarzschild radius of a centimetre or so. That's a rather heavy object to support with a regular coffee table. :) Maybe the coffee table and stand are made from unobtainium.....
by PM 2Ring
Thu May 12, 2016 11:46 am UTC
Forum: Science
Topic: How do we know what electron orbitals look like?
Replies: 8
Views: 3308

Re: How do we know what electron orbitals look like?

This article from 2005 by David Villeneuve Orbital Imaging: Laser-generated high-harmonic radiation produces tomographic images of molecular orbitals describes how to get the shape of the wave function of a molecular electron orbital. Using a computed tomography algorithm, we converted the data to a...
by PM 2Ring
Thu May 12, 2016 11:08 am UTC
Forum: Science
Topic: Which planet?
Replies: 28
Views: 5437

Re: Which planet?

@doogly: Love your work. I feel obliged to throw in a kind word for Mercury. Caloris Planitia is a plain within a large impact basin on Mercury, informally named Caloris, about 1,550 km (960 mi) in diameter.[1] It is one of the largest impact basins in the Solar System. The plain itself is about 685...
by PM 2Ring
Wed May 11, 2016 7:54 am UTC
Forum: Science
Topic: Alkaline Food
Replies: 26
Views: 7411

Re: Alkaline Food

Lutefisk is quite alkaline: pH of 11–12, although it is soaked in water before final preparation, which reduces the pH considerably.

Also, some people use lye as a seasoning. See viewtopic.php?t=96865&p=3211809#p3183323
by PM 2Ring
Sun May 08, 2016 11:54 am UTC
Forum: Mathematics
Topic: Seating problem
Replies: 6
Views: 2851

Re: Seating problem

Here's a Python 2 / Python 3 program that finds solutions. I haven't looked at Flumble's code, but I am using lorb's optimization. My approach is to express the problem as an Exact Cover problem. Our goal is to find sets of 4 permutations so that each of the 10 people get exactly 8 neighbours over t...
by PM 2Ring
Sun May 08, 2016 8:34 am UTC
Forum: Coding
Topic: [Resolved] Generalized Hamming numbers in Python
Replies: 3
Views: 4249

Re: Generalized Hamming numbers in Python

What Xanthir said, although you really only need to worry about m . Here's my version. It creates the generator expressions using a function multiples that takes i and m as args. It would work if you only pass m as an arg, but I think it improves readability to pass them both. My code doesn't use yi...
by PM 2Ring
Sat May 07, 2016 10:59 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

I'm actually going to rewrite in C++ for the performance gains. The full program may take days to run in python. Wise. I love Python, but it's not particularly fast or conservative of RAM. FWIW, in 32 bit CPython a small Python integer (i.e., one that fits into a 32 bit signed machine integer) cons...
by PM 2Ring
Fri May 06, 2016 8:08 am UTC
Forum: Fictional Science
Topic: Fiction Idea: Breaking out of the simulation
Replies: 12
Views: 9412

Re: Fiction Idea: Breaking out of the simulation

Copper Bezel wrote:
Spoiler:
Including the matryoshka doll zinger at the end. Of course, you get that with The Thirteenth Floor and Inception and all of these things, it's basically obligatory....

Spoiler:
It's turtles virtuals all the way down.
by PM 2Ring
Fri May 06, 2016 8:00 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1676: "Full-Width Justification"
Replies: 64
Views: 18191

Re: 1676: "Full-Width Justification"

YMMV, but personally I admire the documentation for FFTW , clearly written by people who have a mastery not only of their topic but of the English language too. It's direct without being overly informal, and has jokes and humorous footnotes that enhance readability without detracting from the clari...
by PM 2Ring
Thu May 05, 2016 8:16 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1676: "Full-Width Justification"
Replies: 64
Views: 18191

Re: 1676: "Full-Width Justification"

My Linotype keyboarding manual talks quite a bit about justification. On a Linotype, automatic justification was achieved by adjusting the space between words with variable width spaces that would evenly divide up the space when the line was sent to cast. [...] ETAOIN SHRDLU Many years ago, I was g...
by PM 2Ring
Thu May 05, 2016 7:39 am UTC
Forum: Science
Topic: Dropping a Cloud Nine From Orbit
Replies: 38
Views: 7072

Re: Dropping a Cloud Nine From Orbit

Maybe I'm missing something here, but I don't see what the big problem is with just constructing the dome on the ground. Of course, it's not going to support its own weight when it's partly built, but why does it need to do that? It's a tensegrity structure, so you just build it flat, with plenty of...
by PM 2Ring
Tue May 03, 2016 7:41 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 590
Views: 112274

Re: Miscellaneous language questions

Spoiler:
Image
by PM 2Ring
Thu Apr 21, 2016 12:33 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1670: "Laws of Physics"
Replies: 46
Views: 12208

Re: 1670: "Laws of Physics"

AFAIK, Feynman did it first. "There were 183 of us freshmen, and a bowling ball hanging from the three-story ceiling to just above the floor. Feynman walked in and, without a word, grabbed the ball and backed against the wall with the ball touching his nose. He let go, and the ball swung slowly...
by PM 2Ring
Tue Apr 19, 2016 8:23 am UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1689293

Re: Today I Learned

Nice round-cut diamond. Do you have Princess and Cushion cuts too? Thanks! No, I only have variations on the Tolkowsky brilliant cut. There's an old POV-Ray include file for a brilliant cut, but I wasn't happy with it, so I made an improved version by referring to Tolkowsky's book: A Study of the R...
by PM 2Ring
Mon Apr 18, 2016 8:28 am UTC
Forum: General
Topic: Lucky Ten Thousand (TIL)
Replies: 13421
Views: 1689293

Re: Today I Learned

... and that the LEDs on the webcam are bright enough to cause positive phototropism: http://i300.photobucket.com/albums/nn9/Sableagle/Demolition%20Ranch%20Barrett/apple_seedlings_zpsey0x1zye.gif Now trying again with a different species, from a higher angle. Interesting! I was going to ask you why...
by PM 2Ring
Mon Apr 18, 2016 8:06 am UTC
Forum: General
Topic: Origami and Mental Illness
Replies: 7
Views: 4538

Re: Origami and Mental Illness

Impressive work, Cleverbeans! FWIW, I've folded quite a few flapping birds over the decades, but never any that tiny. (But I do have a cellophane one on my desk that I folded about 20 years ago).
by PM 2Ring
Mon Apr 18, 2016 7:57 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

Everyone knows the feeling when something that should work, doesn't. Today I got to experience the more rare feeling of something working, which shouldn't. I get uncomfortable when that happens, and if I can't prove to myself why it behaves the way it does I have to change it to something I do unde...
by PM 2Ring
Mon Apr 18, 2016 7:38 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1668: "Singularity"
Replies: 26
Views: 7729

Re: 1668: "Singularity"

And for those who don't know who keithl is, please see Keith Lofstrom , Launch loop , and Keith Lofstrom's Vanity Web Page . wait. wait. ...uhh... ..uh..ok..Tell me. Is our Keith That Keith? ...Well,...ok. ... I'm willing to believe it... We are in the company of some very fine minds. He sure is. F...
by PM 2Ring
Sat Apr 16, 2016 7:31 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1666: "Brain Upload"
Replies: 38
Views: 8360

Re: 1666: "Brain Upload"

So as far as I know, we haven't covered the initial So in this forum (no doubt it's been discussed elsewhere on the board, but...). I quite like it, actually; or at least it doesn't annoy me. It seems to me that so is used in the sense "what I'm about to say follows directly from your question...
by PM 2Ring
Sat Apr 16, 2016 7:07 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1668: "Singularity"
Replies: 26
Views: 7729

Re: 1668: "Singularity"

Keyman wrote:So does the "l" in 'keithl' stand for Leibowitz?


Good call. :) For those who don't get the reference, please see A Canticle for Leibowitz.

And for those who don't know who keithl is, please see Keith Lofstrom, Launch loop, and Keith Lofstrom's Vanity Web Page.
by PM 2Ring
Mon Apr 11, 2016 6:35 am UTC
Forum: Mathematics
Topic: Simplifying expressions with unit'd values
Replies: 13
Views: 3472

Re: Simplifying expressions with unit'd values

What is the meaning of units in the denominator in this case? Can you provide an example of how this would be used and what it would translate to physically? We need ratios of lengths if we want to be able to scale things and ensure the scaled version is a similar shape ( in the sense of similar tr...
by PM 2Ring
Sat Apr 09, 2016 8:40 am UTC
Forum: Mathematics
Topic: Efficient Prizims
Replies: 9
Views: 2451

Re: Efficient Prizims

As gmalivuk said, this is easy to do if you know some calculus, but it's not too hard to verify that s=4 gives the maximum volume for the open box. To make the arithmetic simpler, I'll scale the square down by ¼, so that s=1 and the original square is 6 x 6. The base of the box has length and width ...
by PM 2Ring
Tue Mar 29, 2016 12:40 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

So there's this idea I have about tying chats/media shares like telegram, IRC and WhatsApp (using yowsup) together, but I'm unsure as to what common backend to use. The goal is to have all messages available to any networked device, though preferably messages would be loaded on demand, like a typic...
by PM 2Ring
Fri Mar 11, 2016 6:25 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1654: "Universal Install Script"
Replies: 57
Views: 21418

Re: 1654: "Universal Install Script"

INB4 : Hey this only works if you have a *nix shell running in the first place! Anyone else here old enough to have thought the pip install was referring to this? Anyway, "install" is where horses should be. I'm old enough to have used pip on CP/M, and I was certainly reminded of that pip...
by PM 2Ring
Fri Mar 11, 2016 5:50 pm UTC
Forum: Fictional Science
Topic: New (economically) type of FTL travel
Replies: 16
Views: 9925

Re: New (economically) type of FTL travel

I like it! Each ship has a accuracy parameter (usually between 1.5 and 4, unitless of type distance per distance). Travel between the source point and the actual destination is instantaneous. Specifically the traveler experiences zero/trivial time traveling and arrives at their destination either a ...
by PM 2Ring
Mon Mar 07, 2016 7:15 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

Jplus wrote:I have posted an answer too, which is a bit more efficient.


Nice approach, Julian. I didn't think of doing it like that, but I guess it works if the filtering algorithm accepts an iterator and doesn't need random access or multiple passes over the data.
by PM 2Ring
Sun Mar 06, 2016 10:45 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9968
Views: 1952242

Re: Coding: Fleeting Thoughts

I've been thinking about a SciPy-related problem I can't quite figure out yet. Since my post on Stack Overflow didn't get any replies and none of my friends appear to have a solution either, I figure it can't hurt to ask here as well. Sorry, I didn't even look at your question earlier, since I don'...
by PM 2Ring
Wed Mar 02, 2016 11:17 am UTC
Forum: Mathematics
Topic: Math: Fleeting Thoughts
Replies: 427
Views: 147528

Re: Math: Fleeting Thoughts

Here's a simple way to store a table of primes in a fairly compact form. All primes greater than 5 are obviously coprime to 2, 3, and 5 and hence are coprime to 2*3*5 = 30. IOW, all primes > 5 are congruent to one of (1, 7, 11, 13, 17, 19, 23, 29) mod 30. Note there are 8 numbers in that set, so we ...
by PM 2Ring
Sun Feb 28, 2016 2:39 pm UTC
Forum: Mathematics
Topic: Are all the sequence numbers prime?
Replies: 4
Views: 1499

Re: Are all the sequence numbers prime?

No. The next term in your sequence (after 510767) is 1380265110671180253634405030613336299264996365622991486305858014214261048243081794992210453163935138192156457386571249076356922837629566181477039018950513703169278191952771328537454016440857127805568317159302017023312808646477597452054638680664401...
by PM 2Ring
Sun Feb 21, 2016 6:34 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1643: "Degrees"
Replies: 147
Views: 25336

Re: 1643: "Degrees"

Also, for what it's worth, a black hole of one Planck mass is actually 4 Planck lengths across, ... FWIW, using 2 Planck lengths as the Schwarzschild radius and the formula for I , the entropy in bits, found in the Wikipedia article on the Bekenstein bound , the entropy of that black hole is <= 4π/...
by PM 2Ring
Fri Feb 19, 2016 5:15 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1644: "Stargazing"
Replies: 40
Views: 11393

Re: 1644: "Stargazing"

Also, does "is" imply the object's existence and status in the present tense? (So much of what we see in the sky, after all, no longer exists.) Most of the objects in our sky are within our milkyway. Those objects are, at most, about 100,000 light year away. Thus the info we have on them ...
by PM 2Ring
Wed Feb 17, 2016 3:50 am UTC
Forum: Mathematics
Topic: Infinite Inscribed Squares
Replies: 10
Views: 3169

Re: Infinite Inscribed Squares

Is that from 32 or 64 bit calculations? I'm running Python 2.6.6 on a 32 bit machine. My Python's floats are IEEE-754 doubles, so they have 53 bits of precision. The more accurate value for the area was calculated with 50 decimal digits of precision; I chopped off the last couple of digits, so the ...

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