ciphergoth: (Default)
Paul Crowley ([personal profile] ciphergoth) wrote2008-07-03 11:41 pm
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Powers of two

I can't remember what made me think of this, but there's a bit in Snow Crash about powers of two, and I wondered if things had changed, and that people deal in higher level stuff than this these days. And it's just striking and a bit weird anyway that some people have had occasion to memorize this stuff, I wondered if you had...

[Poll #1217360]

Update: The "powers of two" are just 1+1 = 2, 2+2 = 4, 4+4 = 8, 8+8 = 16 and so on.

Update: it seems like it isn't clear from the above, so for the avoidance of doubt, no-one should feel that they should know this off by heart!
babysimon: (computer lib)

It's easy

[personal profile] babysimon 2008-07-03 10:55 pm (UTC)(link)
0x00000001
0x00000002
0x00000004
0x00000008
0x00000010
etc

;)

[identity profile] alextiefling.livejournal.com 2008-07-03 10:56 pm (UTC)(link)
All except the one that's got the form 32xxx; I can calculate that it must in fact be 32768, but I always forget it when listing them.

[identity profile] valkyriekaren.livejournal.com 2008-07-03 10:58 pm (UTC)(link)
No, I get stuck somewhere in the mid-hundreds, but that's dyscalcula for you - I can't cope with numbers more than two digits long.

[identity profile] damerell.livejournal.com 2008-07-03 10:59 pm (UTC)(link)
Almost. "Ha, he means 65535, what a... no, wait."

[identity profile] olethros.livejournal.com 2008-07-03 11:01 pm (UTC)(link)
Admittedly, I go a bit fuzzy after 4096.

[identity profile] kimble.livejournal.com 2008-07-03 11:05 pm (UTC)(link)
Have to stop and think for a second to get the last two, but basically, 'yes'.

[identity profile] wildeabandon.livejournal.com 2008-07-03 11:15 pm (UTC)(link)
Apparently I can only do up to 12 completely off the top of my head, although the time lag between recalling from memory and calculating the other four is scant seconds.

[identity profile] thekumquat.livejournal.com 2008-07-03 11:57 pm (UTC)(link)
I'd probably only recognise up to 4096. Although once when I was about 6 I set out with vast reams of computer printout paper to calculate how many grains of rice went on the final square of the chessboard. I think I got up to square 40 or so before getting bored of multiplying by two by hand...

[identity profile] elsmi.livejournal.com 2008-07-04 12:13 am (UTC)(link)
16384 is my only shaky one.

I note that right now the poll responses look like: 15, 7, 1. Which is nice.

But does anyone know 2^17?

[identity profile] selectnone.livejournal.com 2008-07-04 12:20 am (UTC)(link)
I get fuzzy after 8192.

Textures for games usually have power-of-two resolutions, and that'd be at the silly end of the image-sizes I'm likely to touch.

(actually, 64x64 is a largish texture for the game I'm working on right now)

[identity profile] phantas.livejournal.com 2008-07-04 12:24 am (UTC)(link)
Computational Number Theory does that to you. I also know or can quickly compute in my head way to many squares, primes, factorisations and square-roots. Back in my teens I computed square-roots with <1% error by head as a party trick (really, it's *way* more easy than it sounds)

[identity profile] marnanel.livejournal.com 2008-07-04 03:04 am (UTC)(link)
To my alarm I find I don't:

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 163oh dammit, 32768, 65536.

The others I can reel off like telephone numbers. Better change my vote.

[identity profile] ephermata.livejournal.com 2008-07-04 03:09 am (UTC)(link)
I can recognize more easily than I can generate, but the lower ones up to 4096 I know reasonably well. They just seem to pop up all over the place, that's all.

[identity profile] aster13.livejournal.com 2008-07-04 06:23 am (UTC)(link)
I don't know what one is. :(

I was an oddity in high school - top sets for science (extra classes and everything!) and third set for maths. No one else was in anything less than top set for maths.

[identity profile] wechsler.livejournal.com 2008-07-04 06:38 am (UTC)(link)
At this time of day I stop at 16384, although I feel I should be able to get to 65536 normally.

[identity profile] keirf.livejournal.com 2008-07-04 07:52 am (UTC)(link)
One of my telephone interview questions is "tell me what 2^10 is" - it's amazing how many candidates claiming to have mathematics or computer science degrees get it wrong. About 7 out of 10.
andrewducker: (Default)

[personal profile] andrewducker 2008-07-04 08:01 am (UTC)(link)
I don't know them off by heart, but I can calculate them in my head up to 8192 - and I'd recognise 16384, 32768 and 65536 instantly.

[identity profile] martling.livejournal.com 2008-07-04 08:22 am (UTC)(link)
Up to exactly that, yes. I also happen to know 2^24.

But I do a lot more low-level stuff than most.

[identity profile] otterylexa.livejournal.com 2008-07-04 09:15 am (UTC)(link)
I get fuzzy after 4096, though I'd recognise the higher ones as "looking like a power of two" and then have to check.

[identity profile] jhg.livejournal.com 2008-07-04 09:30 am (UTC)(link)
I do up to 1,024... after that I have to think about it!

[identity profile] ergotia.livejournal.com 2008-07-04 09:38 am (UTC)(link)
Why would I? I dont need that information in my professional life or my personal life.
ext_78940: (Default)

[identity profile] yoyoangel.livejournal.com 2008-07-04 09:39 am (UTC)(link)
I don't need to do this in my head: I have a pooter.
This leaves more room in my head for the important things, like what to have for breakfast.

[identity profile] ajva.livejournal.com 2008-07-04 09:59 am (UTC)(link)
You bastard. Now I'll have to memorise them.

[identity profile] adjectivemarcus.livejournal.com 2008-07-04 11:56 am (UTC)(link)
I know up to 1024, and then I switch to calculating them, and then to not being bothered to do the maths. Actually, I calculate 2048 and then my brain loses interest immediately, so I don't get to the next one...!

Uploaded textures to Second Life are fitted by the system automatically into powers-of-two dimensions (128x512 and so on), so I do actually use them when making textures in graphics programs. But there's no way I'd need any bigger than 1024.

[identity profile] ladycat.livejournal.com 2008-07-04 12:52 pm (UTC)(link)
I'm afraid I'm not quite sure I even understand what it means?

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