Beefy Boxes and Bandwidth Generously Provided by pair Networks
Think about Loose Coupling
 
PerlMonks  

comment on

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

If, based on your answers in this thread, ultimate goal is better speed after all (and not mysterious slow-downs on every 10th run, about which I have nothing to add), then as usual in case of large arrays, use PDL;. Second pair of results are for 10x $n.

use warnings; use strict; use feature 'say'; use Time::HiRes 'time'; srand( 1 ); my $n = 2e3; my @input = map int rand 1e5, 1 .. $n; my ( $check1, $check2 ); { # original code my $t = time; my @max; push @max, ( sort { $b <=> $a } @input )[ 0 ]; my @sums = @input; for my $i ( 1 .. $n - 1 ){ my $max = -~0; for my $j ( $i .. $n - 1 ){ # HOT-SPOT { ( $sums[ $j - $i ] += $input[ $j ] ) > $max and $max = $sums[ $j - $i ]; # HOT-SPOT } } push @max, $max; } say time - $t; $check1 = pack 'I*', @max; } { # PDL my $t = time; use PDL; use PDL::NiceSlice; my $sums = zeroes long, scalar @input; my $vec = pdl long, \@input; my @max = map $sums( 0 : -$_ - 1 ) -> inplace -> plus( $vec( $_ : -1 ), 0 ) -> maximum , 0 .. $#input; say time - $t; $check2 = pack 'I*', @max; } use Test::More; is $check1, $check2; done_testing; __END__ 0.148595094680786 0.0387320518493652 ok 1 1..1 14.5055229663849 0.759373903274536 ok 1 1..1

In reply to Re: Performance issue in the loop. by vr
in thread Performance issue in the loop. by rsFalse

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 browsing the Monastery: (3)
As of 2024-03-29 06:56 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found