generic image
Processing...
  • Games
  • Catalog
  • Develop
  • Robux
  • Search in Players
  • Search in Games
  • Search in Catalog
  • Search in Groups
  • Search in Library
  • Log In
  • Sign Up
  • Games
  • Catalog
  • Develop
  • Robux
   
ROBLOX Forum » Game Creation and Development » Scripters
Home Search
 

Re: Perfect Numbers

Previous Thread :: Next Thread 
zxv12 is not online. zxv12
Joined: 18 Jul 2009
Total Posts: 286
05 Jul 2012 03:33 PM
Hurro.

I've been finding perfect numbers lately (ok, just today, but stick with me, k?).

Is this a good algorithm?

local HighestFound = 0;
local NumberFound = 0;
local n = 0;
local mf = math.floor;
local A = 0
local c = os.clock;

while true do

n = n + 1;

if n%2 == 0 then
for i = 1, n-1 do
if n%i == 0 then
A = A + i;
end;
end;
end;

if A == n then
HighestFound = n;
NumberFound = NumberFound + 1;
print("\n\n\nHighest perfect number found: "..HighestFound.."\n Number of perfect numbers found: "..NumberFound.."\n CPU time elasped: "..c());
end;

A = 0;

end;


Also, have any of you ever attempted to find perfect numbers? If so, how many have you found, which language, and how did you calculate them?

I'll be looking forward to your replies!
Report Abuse
Trioxide is not online. Trioxide
Joined: 29 Mar 2011
Total Posts: 32902
05 Jul 2012 03:51 PM
[ Content Deleted ]
Report Abuse
zxv12 is not online. zxv12
Joined: 18 Jul 2009
Total Posts: 286
05 Jul 2012 03:53 PM
I've also written a perfect number finder in Python, but I don't know if it's faster or slower yet.

Same algorithm.

n = 1
a = 0
h = 0
f = 0
i = 1

while True:
n += 1
if n%2 != 1:
while True:
if n%i == 0:
a += i
if a > n or i >= n-1:
break
i += 1
if a == n:
f += 1
h = n
i = 1
a = 0
if n >= 496:
break

print("Highest perfect found: "+str(h)+" Number of perfects found: "+str(f))

(Unfortunetly you won't be able to use it unless you intend it yourself. Blame John for crappy forums.)
Report Abuse
BlueTaslem is not online. BlueTaslem
Joined: 11 May 2008
Total Posts: 11060
05 Jul 2012 04:53 PM
Factorization is NP hard. No algorithm will scale well.
Report Abuse
BlueTaslem is not online. BlueTaslem
Joined: 11 May 2008
Total Posts: 11060
05 Jul 2012 04:58 PM
Actually, primality is much easier. And 2^(p−1)(2^p−1) when 2^p - 1 is prime is an even Perfect number. But these are not all of the perfect numbers, just apparently most of them (at least for small numbers).
Report Abuse
HotThoth is not online. HotThoth
Forum Moderator
Joined: 24 Aug 2010
Total Posts: 1176
05 Jul 2012 07:36 PM
@BlueTaslem: I believe that's the case for every even perfect number, and maybe every perfect number (no odd perfect numbers have yet been found). So every known perfect number is of that form, and every number of that form is an even perfect number.

@OP: The algorithm you have will miss odd perfect numbers, if there are any. And if you're just looking for even perfect numbers, probably easier to just increment i by 2 each time and not have a i%2==0 check.

- HotThoth
Report Abuse
HotThoth is not online. HotThoth
Forum Moderator
Joined: 24 Aug 2010
Total Posts: 1176
05 Jul 2012 07:37 PM
And fun fact, if we ever get quantum computers, apparently factoring goes from being hard to being not-so-hard.

- HotThoth
Report Abuse
Combrad is not online. Combrad
Joined: 18 Jul 2009
Total Posts: 11025
06 Jul 2012 07:59 AM
local n = 0
for i = 1,100 do
n=n+1
print(2^(n−1)(2^n−1))
end

? pretty sure mine does thte same
Report Abuse
Radioaktiivinen is not online. Radioaktiivinen
Joined: 25 Apr 2009
Total Posts: 18629
06 Jul 2012 09:08 AM
wiki says dem (even) purfect numbers are liek n 1's followed by n-1 0's (or was it n+1)

idc wat n was tho.


liek

1110000


k
Report Abuse
zxv12 is not online. zxv12
Joined: 18 Jul 2009
Total Posts: 286
06 Jul 2012 09:30 AM
There are no odd perfect numbers.

All perfect numbers are also "Ore's harmonic numbers", and there are no odd Ore's harmonic numbers other than 1.

I'll try the prime method.
Report Abuse
SN0X is not online. SN0X
Joined: 24 Oct 2011
Total Posts: 7277
06 Jul 2012 10:45 AM
Yay I'm unbanned :D

(I was zxv12.)

And I don't get the prime method. When I tried it, it seemed to just spew out random numbers.
Report Abuse
kingkiller1000 is not online. kingkiller1000
Joined: 12 Dec 2008
Total Posts: 26415
06 Jul 2012 11:21 AM
Another fun fact, they've come out with a program for quantum computers already.
Report Abuse
SN0X is not online. SN0X
Joined: 24 Oct 2011
Total Posts: 7277
06 Jul 2012 11:51 AM
Why would finding factors be easier using a quantum computer?

Also, why not just harvest a criminal with a life sentance to jail's brain? :P
Report Abuse
SN0X is not online. SN0X
Joined: 24 Oct 2011
Total Posts: 7277
06 Jul 2012 11:53 AM
"Sorry Jim, I forgot to feed my computer yesterday and now it's dead."
Report Abuse
HotThoth is not online. HotThoth
Forum Moderator
Joined: 24 Aug 2010
Total Posts: 1176
06 Jul 2012 02:02 PM
@SN0X: We don't know that. There are no *known* perfect odd numbers. But we haven't proved that there aren't any. It may be the case that there just aren't any until you get past 10^100000 (this has indeed happened before).

And yeah, true story, it's actually polytime with a quantum computer. Pretty crazy, right? I'm sure wikipedia has a better explanation than I could give of that theorem.


@Combrad: Those will not all be perfect numbers, because that's not necessarily a prime you're starting with; the primality is a necessary condition for even perfect numbers.


- HotThoth
Report Abuse
Combrad is not online. Combrad
Joined: 18 Jul 2009
Total Posts: 11025
06 Jul 2012 02:05 PM
I overlooked that, trying to complete a 3D model of a two hectare area is very disctracting.

Can't be asked to write a new one though.
Report Abuse
Merely is not online. Merely
Joined: 07 Dec 2010
Total Posts: 17266
06 Jul 2012 02:05 PM
^ computer science major above?
Report Abuse
Combrad is not online. Combrad
Joined: 18 Jul 2009
Total Posts: 11025
06 Jul 2012 02:07 PM
Actually.
Landscape Architecture
=D
Report Abuse
Merely is not online. Merely
Joined: 07 Dec 2010
Total Posts: 17266
06 Jul 2012 02:07 PM
I late-posted I was pointing at HotThoth lol
Report Abuse
Merely is not online. Merely
Joined: 07 Dec 2010
Total Posts: 17266
06 Jul 2012 02:08 PM
> factoring will be easy for computers

well there goes RSA encryption...
Report Abuse
Combrad is not online. Combrad
Joined: 18 Jul 2009
Total Posts: 11025
06 Jul 2012 02:08 PM
Close enough.
I appreciate the late post.
Report Abuse
SN0X is not online. SN0X
Joined: 24 Oct 2011
Total Posts: 7277
06 Jul 2012 02:20 PM
Late posts are infuriating.

And yes- perfect numbers might only appear after a certain number, or they might be ultra rare.
Report Abuse
HotThoth is not online. HotThoth
Forum Moderator
Joined: 24 Aug 2010
Total Posts: 1176
06 Jul 2012 04:08 PM
@Merely's late-post: Nop. Not originally :P
@Merely's later, but not late-post: Pretty much. Soon we may all have to switch to some crazy hyperbolic geometry-based encryption scheme or something that sounds equally cool.
Report Abuse
lombardo2 is not online. lombardo2
Joined: 30 Nov 2008
Total Posts: 1604
06 Jul 2012 05:58 PM
Oh right, like the shor's algorithm. We already have quantum computers.
Report Abuse
nightname is not online. nightname
Joined: 10 Jun 2008
Total Posts: 8960
06 Jul 2012 06:16 PM
"We already have quantum computers."

Technically, we also have teleportation, yet it is not available to everyone. Things which are commercial are not usually considered as "out". We all know Google uses quantum computers - but only they can afford to pay a few millions on a single computer, and they have more than one.
Report Abuse
Previous Thread :: Next Thread 
Page 1 of 1
 
 
ROBLOX Forum » Game Creation and Development » Scripters
   
 
   
  • About Us
  • Jobs
  • Blog
  • Parents
  • Help
  • Terms
  • Privacy

©2017 Roblox Corporation. Roblox, the Roblox logo, Robux, Bloxy, and Powering Imagination are among our registered and unregistered trademarks in the U.S. and other countries.



Progress
Starting Roblox...
Connecting to Players...
R R

Roblox is now loading. Get ready to play!

R R

You're moments away from getting into the game!

Click here for help

Check Remember my choice and click Launch Application in the dialog box above to join games faster in the future!

Gameplay sponsored by:
Loading 0% - Starting game...
Get more with Builders Club! Join Builders Club
Choose Your Avatar
I have an account
generic image