Your first point, unluckely is not applicable, due to the fact that depending on the element in @{$categories{$k}->{traces}} matched, the sum below will be applied to a different element in the @lista array.

I don't understand what you're saing. The code you showed us changes neither %categories nor $k. Why should anything change if you do the lookup outside the loop? 

my @a = @{$categories{$k}->{traces};
OUTER: while( my $line = <GZIP> ) {
    for ( my $i = 0; $i < @a }; $i++ ) {
        if ( $line =~ /^($a[$i]->{regex})/ ) {
            my @lista = split /;/, $line;
            $A += $lista[$a[$i]->{calc}}[0]];
            $B += $lista[$a[$i]->{calc}}[1]];
            $C += $lista[$a[$i]->{calc}}[2]];
            next OUTER;
        }
    }
}

[download]

This should do exactly the same as your code, only more efficient.

The version with while is at least as fast as the version with for, and uses much less memory.

Still I'd like to emphasize my first point again: Benchmark and profile before starting to optimize (and before even thinking of parallelization).

In reply to Re^3: An efficient way to parallelize loops by moritz
in thread An efficient way to parallelize loops by Deus Ex

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!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • 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, details, 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, summary, 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.