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From Doug MacEachern <do...@covalent.net>
Subject Re: cvs commit: modperl-2.0/lib/ModPerl Code.pm
Date Fri, 14 Apr 2000 17:23:39 GMT
> > Orwant and friends in "Algorithms with Perl" page 28 claims the first form
> > is slower.

faster to *parse*, not faster to *run*.  stas, your benchmarks don't test
parse time.
 
> It seems that TIMTOWTDI is going to die soon as everybody tells me that I
> should code as shown in "OO Perl" and ""Algorithms with Perl" :( 
> 
> The books are cool, but why turning them into bibles? The book authors are
> great, but why rising them into gods? 

bibles?  gods?  i haven't touched either of these books.  i'm using '' vs.
"" because '' is faster for Perl to parse and faster for me to parse.
i'm thinking about string usage more, rather than just slinging them
around without a care.  i'm trying to avoid interpolation, which turns
into concatination, which uses more memory and is slower than using a
list.  if i see a '' string, i don't worry, if i see "", i want to look
close and thing about how expensive it will turn out to be.

there will be exceptions, like "\n", ' define' vs "\ndefine", i do prefer
the later for readability.  in fact, there's plenty of interpolation
happening in those modules, i very much value readability, and the 
"\n", ' define' did make me cringe a bit.  and i will probably change that
one back.

and, your benchmark of those shows "\ndefine" to be faster, because
the string being copied is so tiny, it's less expensive than pushing an
extra item onto the stack.  when generating webpages, we generally don't
deal with such tiny strings, do we?

use Benchmark;

open my $fh, '>', '/dev/null';

my($one, $two, $three, $four) = map { $_ x 1000 } 'a'..'d';

timethese(300_000, {
                 concat => sub {
                     print $fh "$one$two$three$four";
                 },
                 list => sub {
                     print $fh $one, $two, $three, $four;
                 },
});

Benchmark: timing 300000 iterations of concat, list...
    concat: 12 wallclock secs (10.83 usr +  0.67 sys = 11.50 CPU) @
26086.96/s (n=300000)
      list:  9 wallclock secs ( 6.75 usr +  0.59 sys =  7.34 CPU) @
40871.93/s (n=300000)



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