I definitely think benchmarking is the key answer here.

I think no matter what, this is an implementation specific problem. I always wrote Perl for
programmer speed, and paid less attention to execution speed. Until I started working on problems
that were big enough to deal with datasets ranging from hundreds of meg to a few gig in size.

I love Perl but for data this big, and the bit of processing required, I would have initially went
with either C or C++. BUT - I work in a place where most everyone knows Perl and not many know C/C++
so Perl optimization has become a big issue.

I've learned a lot about how slight code changes can increase efficiency, especially when
certain tasks need to be done many times over. I've seen major speed increases
just by benchmarking and trying a different solution, but keeping the same algorithm.
Things especially like 
my @a = ();
if ( $foo =~ /^(\d+)\s+(\w+)\s*$/ ) {
    @a = ($1, $2);
}

[download]
vs. 
my @a = split (/\s+/, $foo);

[download]


Guess what? In my system, option #1 runs about 90% faster.


-felonious --

In reply to Re: Optimizing existing Perl code (in practise) by feloniousMonk
in thread Optimizing existing Perl code (in practise) by JaWi

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