Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw
 
PerlMonks  

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

Here is one way to make it 30x 150x faster using your 5000 random number bench. Kinda cheating of course and still room for more optimisation.

[root@devel3 root]# time ./trinum.pl >out real 0m41.310s user 0m41.310s sys 0m0.000s [root@devel3 root]# time ./trinum_c2.pl >out real 0m0.276s user 0m0.280s sys 0m0.000s [root@devel3 root]# more trinum_c2.pl #!/usr/bin/perl use Inline 'C'; my $file = $ARGV[0] || 'targets.txt'; open (INPUT, '<', $file) or die "Unable to open $file for reading : $! +"; while ( <INPUT> ) { chomp; get_three( $_ ); } __END__ __C__ #include <math.h> #define TRI(i) (i*(i+1)/2) int get_three ( int num ) { register max,target,i,j; max = (int)sqrt((double)(2*num)); while ( max != 0 ) { target = num - TRI(max); for( i=0;TRI(i)<=target;i++ ) { for( j=0;j<=i;j++ ) { if ( target == (int)(TRI(i)+TRI(j)) ) { printf( "%d, %d, %d\n", TRI(max), TRI(i), TRI(j) ) +; return 1; } } } max--; } printf( "Something went horribly wrong : %d\n", num ); return 0; } [root@devel3 root]#

This was the original try which was only 30x faster and took over a whole second to run :-)

[root@devel3 root]# time ./trinum_c.pl >out_c real 0m1.158s user 0m1.150s sys 0m0.000s [root@devel3 root]# cat trinum_c.pl #!/usr/bin/perl use Inline 'C'; my $file = $ARGV[0] || 'targets.txt'; open (INPUT, '<', $file) or die "Unable to open $file for reading : $! +"; while ( <INPUT> ) { chomp; get_three( $_ ); } __END__ __C__ #include <math.h> int p_tri( int num ) { double x; int t; x = ( sqrt( 8 * (double)num + 1 ) + 1 )/ 2; t = (int)x; return (double)t == x ? 0 : t; } int get_three ( int num ) { register prev,i,j,tri; if ( ! (prev = p_tri( num )) ) { printf( "%d, 0, 0\n", num ); return 1; } while ( --prev ) { for( tri=prev*(prev+1)/2,i=0,j=num-tri; j>=i; j--,i++ ) { if ( 0==p_tri(i) && 0==p_tri(j) ) { printf( "%d, %d, %d\n", tri, i, j ); return 1; } } } printf( "Something went horribly wrong : %d\n", num ); return 0; } [root@devel3 root]#

cheers

tachyon


In reply to Re: Triangle Numbers Revisited by tachyon
in thread Triangle Numbers Revisited by Limbic~Region

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



  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?
    Username:
    Password:

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

    How do I use this? | Other CB clients
    Other Users?
    Others having an uproarious good time at the Monastery: (6)
    As of 2015-07-31 06:38 GMT
    Sections?
    Information?
    Find Nodes?
    Leftovers?
      Voting Booth?

      The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









      Results (274 votes), past polls