## Blue Gene/P Reaches Sixty-Trillionth of Pi Squared 212 212

Reader Dr.Who notes that an Australian research team using IBM's Blue Gene/P supercomputer has calculated the sixty-trillionth binary digit of Pi-squared, a task which took several months of processing. Snipping from the article, the Dr. writes:

*"'A value of Pi to 40 digits would be more than enough to compute the circumference of the Milky Way galaxy to an error less than the size of a proton.' The article goes on to cite use of computationally complex algorithms to detect errors in computer hardware. The article references a blog which has more background. Disclaimers: I attended graduate school at U.C. Berkeley. I am presently employed by a software company that sells an infrastructure product named PI."*
## Different outcomes (Score:5, Funny)

From the blurb:

Oh, I expected the sentence to end with, "...and I still don't know why the fuck anyone cares about a number this long."

I'm going to the bar. Who's with me?

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Well, I'm going to Pi. http://www.restaurantpi.com/ [restaurantpi.com]

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why the fuck anyone cares about a number this long

Seriously, does anyone have an answer for this? Unless they're waiting to see if the digits start repeating themselves, I don't get why anyone would need a value of pi to be so precise.

Personally, I've assumed that the stupidly-precise values of pi were calculated out of pure obsessiveness and, perhaps, a desire for fame (of a kind).

But if they're using months of time on a very expensive, very new, publicly-funded supercomputer to calculate the value, then there's _got_ to be a reason. Right?

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After waiting minutes for an answer, I decided to RTFA and, well, there is a reason (or at least a good excuse)

one application for computing the digits of Pi is to test the integrity of computer hardware and software, which is a focus of Baileyâ(TM)s research at Berkeley Lab. âoeIf two separate computations of digits of Pi, say using different algorithms, are in agreement except perhaps for a few trailing digits at the end, then almost certainly both computers performed trillions of operations flawlessy"

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I don't buy it.

Trillions of operationslater we know the Sixty-trillionth binary digit of pi squared is 1 and the hardware is flawless or 50/50 chance it got luckyFifty-fifty, huh?

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Tiny but non-zero probabilities make mathematicians sleep restlessly. It's just untidy.

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They are secretly looking for the digits to form an infinite series of encoded bitmaps of a circles, in order to prove that god has a sense of humour.

--jeffk++

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why the fuck anyone cares about a number this long

Because... if we have more binary digits of Pi, we can search for subsequences of digits representing mp3 songs. Using that, we can show that RIAA is wrong, because as a matter of fact, you can't copyright mathematics.

## Re: (Score:2)

This reminds me of an altercation on one of the newsgroups a few years back, and I quote:

> > In article eugene@ames.UUCP (Eugene Miya) writes:

> > >We have just received a letter from Japan that a newer record for

> > >computation of digits of Pi was accomplished. Previously David Bailey

> > >here at Ames did a 30 million digit computation on the Cray-2.

> > >The new computation was done on an older Hitachi 810 supercomputer

> > >using extended storage. The n

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Well, pi just has an infinitely long period. :-)

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yeah, pretty sure you are either not from australia or you are just trolling here.

i am from australia. i know no one who 'wants to be american'. american education is a laughing point in australia (not entirely deserved i guess, but mostly focused on the more prevalent influence of religion in 'science' education in some parts of america).

not sure what the screech crap was there, but i'm sure you thought it was hilarious.

apologies to everyone else for feeding the troll.

## pi Squared? (Score:2)

What does that number "do"?

Pi is famous, and the more well known number to crunch. Why crunch Pi Squared? Can't you just square Pi?

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Can't you just square Pi?

Well, yes, but doing so to vast precision requires you to to crunch a vast number of digits of pi, so I imagine it's all largely the same in the end.

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Yep. Squaring a number is an O(n^2) operation.

Squaring a number with a naive algorithm is. With some decent algorithm it is O (n ln n). Like multiplying, division, square root, sine, cosine and many other functions.

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What does that number "do"?

Well, for one thing, you could use it to defeat computers in the future.

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Pi is 'wrong' ... http://tauday.com/

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It's in section 2.3, where he shows that e^(i tau) = 1.

Was it tl;dr? I'm not even average at maths compared to most /. posters, and even I could read the whole thing.

## How many digists of pi do you know? (Score:3, Informative)

http://www.toothpastefordinner.com/031208/how-many-digits-of-pi-do-you-know.gif [toothpastefordinner.com]

## Re:How many digists of pi do you know? (Score:4, Interesting)

Re:How many digists of pi do you know?

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3.14159265358979323846264338327950288.

Yep. Still got them. But I can only recall by reciting them aloud.

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about 5 probably. My daughter can recite 50 or 100 or something like that.

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"50 or 100 or something like that"?

That's like saying you have "1 or 2 cars or something like that" -- far too imprecise to be useful. In fact, 0 would satisfy "50 or 100 or something like that".

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Ha ha.... while true, I sympathize with the grandparent. My daughter is also a Pi digit memorizer. She adds a few digits every so often, I can't keep track of how many she knows. I'd guess 75 or 100 or something like that. :) I don't think she knows or cares exactly how many digits of Pi she has memorized, as long as it is more digits than anyone else she meets...

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## Re:How many digists of pi do you know? (Score:5, Informative)

I know all of them. I just don't know which order they go in.

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OK I'm a dick.

50.

## Re:How many digists of pi do you know? (Score:5, Informative)

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"How I want a drink, alcoholic of course, after the heavy lectures involving quantum mechanics!" There you go, Pi to 14 digits in an easy to remember package. Count the letters in each word to get the right digits.

Easily beaten by this common and far more memorable verse:

How I wish I could enumerate Pi

"Eureka!" cried the great inventor

"Christmas pudding, Christmas pie

is the problem's very center!"

After hearing that one once, I could not help but remember pi to 20 decimals.

If I want to be more precise, arccos(-1) will do.

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In mystic force and magic spelling

Celestial sprites elucidate

All my own striving can't relate

Or locate they who can cogitate

And so finally terminate.

Finis.

I did it backwards: I memorised the digits of pi directly, and use them to check my recollection of the verse. That's also as far as you're going in simple letter-counts, as the next digit is a zero.

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## YTMND inspired a lot of people to learn (Score:2)

## Not a disclaimer ... (Score:2, Informative)

"Disclaimers: I attended graduate school at U.C. Berkeley. I am presently employed by a software company that sells an infrastructure product named PI.""

That's *not* a DISCLAIMER. That's a DISCLOSURE.

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Doesn't that bring us back to the word 'disclaimer'?

## And yet (Score:2)

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## Balls (Score:2)

1.67E-13 is FAR larger than 2^-6E13. Stupid math.

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## And the answer is... (Score:2)

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## Error in, error out (Score:2, Interesting)

... enough to compute the circumference of the Milky Way galaxy to an error less than the size of a proton

Why bother carrying out the computation to such precision when the error in your measurement of the radius (or diameter) would be so much bigger.

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It sounds like you think that's a statement about the pi they've calculated here, where the words immediately preceeding your quote, found at the top of this page, are "pi to 40 digits". Any of us could comfortably calculate that on paper in a day, or half an hour with a 10-digit solar powered calculator. I fear you may be guilty of slashdot-itis - an impulse to try and prove yourself smart by demolishing a strawman built from the headline, or the summary if we're lucky. Sometimes, the fail is too epic not

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Woosh!!

## Pi r round (Score:2)

Not square.

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Not square.

Besides, a square pi is more of a cobbler, don't you think?

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Back in the land where I was born we had 'meat pies'. They weren't square exactly, more like rectangular with rounded corners.

(No Apple Computer (TM) had nothing to do with it.)

I only ever bothered memorizing 10 digits of Pi since that was the number of digits calculators had (back in '74 - it was an HP35

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In Ye Olde Country, the strangest meat pie was the crescent-moon-shaped Cornish pastie.

## BG/P (Score:2)

Wow, a BlueGene/P is being used to run something other than Linpack. That's gotta be a first.

Disclaimer: I didn't attend graduate school at U.C. Berkeley, nor am I presently employed by a software company that sells an infrastructure product named PI. I have, however, wasted way too much time trying to get codes to build and run (slowly!) on BG/* platforms.

## Easy to calculate (Score:3)

It's plain easy to calculate the sixty-trillionth digit of Pi... as long as you don't care about the digits that come before it: http://www.sciencenews.org/sn_arc98/2_28_98/mathland.htm [sciencenews.org].

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20 computers a month for the trillionth, much less all 60... trillion. A month with 20 computers for one digit still doesn't seem that straight forward.

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GP point is that computing a particular digit of pi is easy, you can even compute it manually. So in particular the 60 trilionth digit is easy to know. Knowing the first 60 trilionth digit is a much harder task.

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you still have to do an amount of work proportional to 60 trillion

Actually, Wikipedia [wikipedia.org] lists the runtime of computing the nth digit of pi as O((n log n)^3) using the original BBP algorithm. Apparently this has been improved O(n^2). I'm not sure what the runtime of algorithms which compute the first n digits of pi are.

## Base 10 - Bah! (Score:2)

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You humans and your base-10 arithmetic. I use base-pi arithmetic. So pi = 1, and pi squared = 1. Computed in a nanosecond. Of course, it makes other computations slightly more complex. For example, I have about 3.183095825842514 fingers, more or less...

You just took 10 and divided it by pi and wrote that down, all in base 10. Also, pi in base pi would be 10, not 1 (like 2 is 10 in binary), and pi^2 is 100.

I'm not certain how other numbers in a non-integer base would be written down, but I think 10 in base pi would be 100.010221222... (pi^2 + pi^-2 + 2*pi^-4 + 2*pi^-5...) There may be multiple representations of the same number. For example, I think 10 could also be 30.121...

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## What a waste of time! (Score:2)

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## Well??!? Is it 1 or 0? (Score:2)

Of course, this being slashdot, I didn't RTFA.

## Universe (Score:2)

Question: Knowing the diameter of the observable universe, how many digits of Pi are needed to calculate the circumference of the observable universe, accurate to within 1 plank length?

Answer: 62 digits. Here they are: 3.14159265358979323846264338327950288419716939937510582097494459

Calculated this one myself.

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## A time to crack wise... (Score:3)

I think it would be tremendously funny to find out, at some suitably ridiculous decimal place, that all subsequent places are zero repeating. It would utterly break some people's heads to find out that the number is only "very, very particular," rather than "irrational."

It is the one hope that holds my interest when I read about crunching these numbers.

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I'm sorry to destroy your one hope. [wikipedia.org]

## Feynman point (Score:2)

There is a sequence of several 9's [wikipedia.org] fairly early in the decimal expansion of pi though. People have joked about memorizing pi out to 770 digits so they can say "...999999 and so on."

But seriously, the irrationality of arctan(1) (which equals tau/8 or pi/4) has been proven [wikipedia.org].

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## Bring the measuring tape. (Score:2)

'A value of Pi to 40 digits would be more than enough to compute the circumference of the Milky Way galaxy to an error less than the size of a proton.'

I freaking love mathematicians. Everything has a proof when you can't actually prove it, coming or going.

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## Cliff-hanger (Score:2)

What IS the sixty trillionth digit of Pi? That's what I'd like to know.

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## Re:Only one binary digit? (Score:5, Funny)

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1, in base pi.

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## Numberists! (Score:3)

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They should calculate pi*e. Knowing that number to such detail would be... delicious.

That's a pretty sweet comment

## Re:Numberists! (Score:5, Interesting)

Especially given that pi is a stupid constant that makes no sense [tauday.com].

## Tau? (Score:2)

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thanks, i found that link really interesting :)

i like when something i had thought in the back of my head while doing school work (way back when) turns out to be something other people have pondered over. it is remarkable to see how much more 'pretty' the maths becomes with this simple change of perspective.

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But there might be a circle in there.

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solid angle

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