As I noted, C is the language for the job. It doesn't really matter how efficient the regex solution, C can work on the data in-place without incurring much in the way of dynamic allocation costs. You have mitigated this disadvantage to an extent in your version by placing certain limitations on the algorithm, notably the 500 unit capture max. This changes the situation considerably. However the design you chose isn't competitive unfortunately :/ primarily I suspect because its not an optimised line within the re engine to be used like this, although that is conjecture sicne i'm not familiar with the internals. 

Length: 1920
Enlil 2:    0.93203s
Dingus 1:   0.530455s
Dingus 2:   0.537765s
Rasta 1:    1.973259s
TommyW 1:   0.87257s
Robartes 1: 0.996671s
PhiRatE:    0.232084s
BrowserUk:  2.764623s

edit: note that this is for 100 iterations

With the code done like this: 

# BrowserUk
$t0 = [gettimeofday];
#! Set up big regex. 1-time hit.
my $re ='(?:(.)(??{"$+*"}))?' x 500; $re = qr/$re/o;
for (1..100) {
    @res = browseruk($stn);
}
print "BrowserUk: ".tv_interval( $t0 )."\n";

sub browseruk {
    $_ = shift;

    my @c =  m/$re/; #! THIS LINE DOES ALL THE WORK.

    #! This truncates the list to exclude null matches returned from r
+egex.
    $#c = $#- -1;

    return \@c;
}

[download]

I anticipated that perhaps the startup cost of the regex generation might be causing the performance problem, so I ran a 1000 unit test as well, against only my entry. 

Length: 1920
PhiRatE:    2.241276s
BrowserUk: 28.384692s

Note that you got similar results, I'm running 100-1000 runs of the same line, you only did one :)

My recommendation is either go with the Inline C one if you really need the speed, or Dingus' 2nd variant, which is the cleanest, closest perl variant.

In reply to Re: Re: Re: Re: Efficient run determination. by PhiRatE
in thread Efficient run determination. by BrowserUk

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