1.7 Billion Digits Of Pi On CD

H0ek writes "Not that there is any use for this whatsoever, but there is a torrent available for 1.7 billion digits of pi on a CD. The data is everything after the '3.' on one line, bzipped. There are a couple of the Cygwin tools on the disk as well as source for a small search tool (because grep just didn't cut it this time). Inside the ISO there's links to the source of the data, in case you want the rest of the 4.2 billion digits available. Wear your geek badge with pride! Be the first kid on your block to have the entire set!"

Comments

Useless?

[Xaroth]

"Not that there is any use for this whatsoever..."

I'm not so sure. Given that there are all sorts of interesting things about the number (a quick google search turned up this as an example), having a CD with the first couple billion digits could be useful for anyone playing around with statistical analysis of it.

Re:Useless?

[museumpeace]

Far be it from me to step in a pile of God doodoo, especially on /. but...
There is a pattern of sorts in the digits of Pi. Providing you don't mind working in hexadecimal, [why that base and no other?...any math PhD's in the audiance?] formula 29 on this page gives you a way to calculate any arbitrary digit of Pi without running a series calculation up to that digit's precision. If a formula for any digit, with independence from all other digits doesn't stretch the definition too much, I'll call it a pattern in the digits of Pi.
I for one welcome a creator who would leave us such puzzles.

Alas, firewalls...

[CAlworth1]

While there is probably nothing useful that I could do with this file, there is also no way for me to be able to get it, even if I had something to do with it - One of the wonderful things about going college in the day and age where it is bad to share information is that bitTorrent is not allowed.... mirror of pi anyone?

Having said that, it seems interesting to be asking, literally, for a mirror of the real world - as numbers go, this is pretty real.

Go to pi.com! ;-)

[xmas2003]

http://3.14159265358979323846264338327950288419716 9399375105820974944592.com/ which is the longest you can do in DNS currently ...

Re:Shouldn't compress well

[slamb]

At first, I was thrown off by the idea of compressing something like pi, as it shouldn't compress. The answer is that they're storing ASCII decimal digits, which require less than 4 bits per number, instead of 8. So you should get at least a 50% compression ratio, which would be 850 million bytes. But it's actually 3.something bits of information per byte, so they're able to fit it on a CD. I would be surprised if bzip could do any better than that.

I had the same thought. To put it in dirt-simple terms, they're only using 10 out of the 256 possible values in every byte, due to the ASCII encoding. This is how bzip2 is able to find any redundancy; pi itself has none.[*]

So the best compression ratio (just compressed size/uncompressed size, right? so lower is better) is ln(10) / ln(256) = 41.5%. On a 700 MiB CD with no filesystem and nothing but pi, this means 700 * 2^20 / ln(256) * ln(10) = 1.77 billion digits (1767655840, with almost room for one more).

You'd do better than bzip2 by just using fixed blocks of N bytes to represent M digits. (Larger choices would get you closer to that best ratio; lower choices would less work to decode each block, which might make seeking more practical and reduce memory requirements.) This would be superior to bzip2 in that it'd get somewhat better compression, use a lot less CPU time, and be seekable. You could encode and decode with a one-line Perl script.

[*] - I suppose you could simply include the algorithm they used to generate the digits...but it'd take a long time to run, negating the whole point of putting pi on a CD.

Uncountable versus countable infinities

[benhocking]

Better yet, since pi only contains a countable number of infinite digits, and there are uncountably infinite numbers of problems (see any decent book on theory of computing), the digits of pi most likely solve an infinite number of problems. Of course, since we can only describe a finite number of problems (in a finite amount of time), there are far fewer of these. The digits of pi do solve, for example, the problem of the ratio of a circle's circumference to its diameter. Of course, the question we're really looking at is what are the digits telling us in some non-geometrical sense (presumably), and, better yet, is there anything they're telling us that is independent of the number base (e.g., decimal vs. binary vs. trinary)? Of course, your argument still holds.

Re:Wow.

[H0ek]

Less than two hours after the posting of the article to the public it's hit 6 seeders. Let me present to you your BRICK.

This from a site on a 500MHz P3 sitting on a little cable modem on a public utility style ISP providing 100KB/s upload speed. I love BitTorrent.

Algorithm

[FullMetalAlchemist]

Does anyone have a link to the algorithm where one can calculate the digits of pi at any given position without knowing the result from the preceding digits?

PI server

[JVolkman]

http://3.14159265358979323846264338327950288419716 9399375105820974944592.jp
I believe this server keeps sending digits of PI indefinitely (most likely using the fun Nth-digit-of-PI formula). It's already a slow site, and will probably be slashdotted quickly. (This is not a dupe of the .com posted earlier)