I am trying to use the following computation: 232582656(232582657-1)

n = (2**32582656) * (2**32582657 - 1)

I am getting the msg:

perf.rb:5: warning: in a**b, b may be too big Infinity

Any help will be appreciated.

Thank you

Victor

I am trying to use the following computation: 232582656(232582657-1)

n = (2**32582656) * (2**32582657 - 1)

I am getting the msg:

perf.rb:5: warning: in a**b, b may be too big Infinity

Any help will be appreciated.

Thank you

Victor

You do realize the magnitude of number you’re trying to calculate? There

IS

a limit to how big even BigNum can go before deciding to crap out. I’d

like

to see someone try this in Lisp. If that interpreter can’t handle it,

then

no language can.

Jason

On Sat, May 05, 2007 at 02:10:58AM +0900, Victor R. wrote:

I am trying to use the following computation: 232582656(232582657-1)

n = (2

32582656) * (232582657 - 1)

Homework question? Brute force probably isn’t the way

Brian,

Actually, NO. This is not a homework questions. It is, however and

unfortunately, an issue of my deficiency and lack of knowledge of the

language.

For pure and simple intellectual curiosity, I am attempting to write a

ruby

pgm to find perfect numbers.

The largest perfect number found to this date, if I believe website

http://amicable.homepage.dk/perfect.htm is: (2**32582656) *
(2**32582657 -

1).

Been the neophyte that I am, I thought about picking it up from there

and

play with it, since I have at my disposal a very large IBM

multiprocessor

environment.

I know that Brute force is not the way, but I don’t have a nice

algorithm to

use.

Thank you

Victor

On May 4, 2007, at 10:36 AM, Jason R. wrote:

You do realize the magnitude of number you’re trying to calculate?

There IS

a limit to how big even BigNum can go before deciding to crap out.

I’d like

to see someone try this in Lisp. If that interpreter can’t handle

it, then

no language can.

Python 2.5 appears to have handled the expression easily enough (3-4

seconds on my iMac Intel Core Duo). Converting it to a string for

display seems to be taking quite a long time, which isn’t too

surprising since it should have nearly 2 million decimal digits

(according to log10(n)).

-Mark

For the record, I am running ruby 1.86 under AIX 5.3.

If the answer is that it can be done on Ruby, that’s an OK answer also.

If

this is the case, I start playing with Python, at least for this

problem.

Thanks

Victor

On Sat, May 05, 2007 at 04:34:01AM +0900, Victor R. wrote:

The largest perfect number found to this date, if I believe website

http://amicable.homepage.dk/perfect.htm is: (232582656) * (232582657 -

1).

Then that’s the number, represented in a compact form.

I know that Brute force is not the way, but I don’t have a nice algorithm to

use.

But what are you trying to achieve? Simply to display this number in its

direct decimal form?

If my rusty maths is correct, that number is a little under

2**(32582656 + 32582657)

which is roughly 10 ** ( (32582656 + 32582657) * log(2)/log(10) )

~= 10 ** 19616713

So there are nearly 20 million digits in the answer…

— Victor R. [email protected] wrote:

For the record, I am running ruby 1.86 under AIX

5.3.

If the answer is that it can be done on Ruby, that’s

an OK answer also. If

this is the case, I start playing with Python, at

least for this problem.Thanks

Victor

p 2048 ** 31819 - 1024 ** 31819

or

a = 1

32582656.times { a *= 2 }

b = a

32582656.times { b *= 2 }

p b - a

Todd, thank you for the example. I truly appreciate it. I’ll give it a

try.

Victor

I said:

p 2048 ** 31819 - 1024 ** 31819

Oops. Ignore this one. I don’t know what I was

thinking

— Todd B. [email protected] wrote:

— Victor R. [email protected] wrote:

Todd, thank you for the example. I truly

appreciate

it. I’ll give it a try.Don’t get too excited. On my system (2.4GHz Intel),

it looks like it would take about 2.5 hours to

compute

minute on my system:

a = 2 ** (2**10 * 9)

b = 1

3541.times { b*=a }

s = b.to_s

— Victor R. [email protected] wrote:

Todd, thank you for the example. I truly appreciate

it. I’ll give it a try.

Don’t get too excited. On my system (2.4GHz Intel),

it looks like it would take about 2.5 hours to compute

(I didn’t test it to see if it would even work).

Also, it is most likely faster to multiply by larger

numbers than 2.

2**32582656 == 4**16291328 == 16**8145664 ==
256**4072832 == 65536**2036416 and so on

Broken down, it’s:

2**32582656 == 2**(2**10 * 3**2 * 3541) ==

( (2**(2**10))) ** (3**2) ) ** 3541

I’m guessing now matter how you cut it up, you will

get the same error, though Maybe ruby chokes at

around a million digits.

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