On Sep 29, Hanson, Rob said:
>I ran some benchmarks.
>
>The two-liner outperformed the one-liners by a 10 to 1 ratio. Code and
>results below.
>
>Benchmark: timing 100000 iterations of OneLine, OneLine2, TwoLines...
> OneLine: 41 wallclock secs (39.30 usr + 0.00 sys = 39.30 CPU) @ 2544.79/s
> OneLine2: 34 wallclock secs (32.58 usr + 0.00 sys = 32.58 CPU) @
>3069.56/s
> TwoLines: 3 wallclock secs ( 2.58 usr + 0.00 sys = 2.58 CPU) @
>38789.76/s
You'll get a better representation with the following benchmark:
#!/usr/bin/perl
use Benchmark 'cmpthese';
my $s = " " . join(" ", ('foo') x 100) . " ";
cmpthese(-5, {
capture => \&capture,
alt => \&alt,
two => \&two,
two_rev => \&two_rev,
});
sub capture {
my $copy = $s;
$copy =~ s/^\s*(.*?)\s*$/$1/s;
}
sub alt {
my $copy = $s;
$copy =~ s/^\s+|\s+$//g;
}
sub two {
my $copy = $s;
s/^\s+//, s/\s+$// for $copy;
}
sub two_rev {
my $copy = $s;
$copy =~ s/^\s+//;
($copy = reverse $copy) =~ s/^\s+//;
$copy = reverse $copy;
}
The output is thus:
Benchmark: running alt, capture, two, two_rev for at least 5 CPU seconds
alt: 5 wallclock secs @ 4163.86/s (n= 21777)
capture: 5 wallclock secs @ 4876.60/s (n= 25846)
two: 6 wallclock secs @ 24841.44/s (n=130666)
two_rev: 5 wallclock secs @ 148958.27/s (n=774583)
Rate alt capture two two_rev
alt 4164/s -- -15% -83% -97%
capture 4877/s 17% -- -80% -97%
two 24841/s 497% 409% -- -83%
Notice the string this time. It's got embedded whitespace. This causes
the '\s+$' regex to perform HORRIBLY. If you want to see why, try this:
perl -mre=debug -e '"abc def ghi jkl mno" =~ /\s+$/'
Notice that the string "abc def... mno" doesn't end in whitespace, but
that the engine checks for /\s+$/ at each chunk of whitespace. Icky
awful.
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
[ I'm looking for programming work. If you like my work, let me know. ]
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