Beefy Boxes and Bandwidth Generously Provided by pair Networks
go ahead... be a heretic
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??

tilly's comment about things being "nearly linear" threw me for a bit. Then I realized that the quadratic nature is countered by the outer loop only needing to run to sqrt(N) and the inner loop being somewhat similarly restricted.

Which made me realize that my solution was suboptimal. Here is a faster one at the same number of characters [ thanks to MeowChow noting that I'd stupidly left in a trailing semicolon in my previous one ;) ]:

sub sieve3 { grep{@_[map$a*$_,$_..@_/($a=$_)]=0if$_[$_]>1}@_=0..pop } # ^^ for( @ARGV ) { print "$_: ",join(" ",sieve3($_)),$/; }

In playing with this and verifying that I didn't break it, I noticed something interesting and expanded on it. For how long of a stretch can you go without hitting any prime numbers? Well, stopping at 0.5million (because of memory limits), here are the results. "xN" means there were N ties before a new "winner" appeared:

2=5-3(x2) # 3..5, 5..7 4=11-7(x3) # 7..11, 13..17, 19..23 6=29-23(x7) 8=97-89 14=127-113(x3) 18=541-523 20=907-887 22=1151-1129 34=1361-1327(x2) 36=9587-9551(x3) 44=15727-15683 52=19661-19609(x2) 72=31469-31397 86=156007-155921(x2) 96=360749-360653 112=370373-370261 114=492227-492113

        - tye (but my friends call me "Tye")

In reply to (tye)Re3: (Golf): Sieve of Eratosthenes by tye
in thread (Golf): Sieve of Eratosthenes by tilly

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others chilling in the Monastery: (5)
As of 2024-03-29 08:26 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found