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Re: Re^2: Never (qr//)

by grantm (Parson)
on May 14, 2003 at 09:46 UTC ( #258014=note: print w/replies, xml ) Need Help??


in reply to Re^2: Never (qr//)
in thread Never-to-use Perl features?

You're right, publishing a benchmark without the test data is pretty meaningless. Here's a revised version that uses the individual words output from 'perldoc -t perlfunc' as the test data.

#!/usr/local/bin/perl -w use Benchmark; my (@words, $count); open(TESTDATA, "perldoc -t perlfunc|") || die $!; while(<TESTDATA>) { chomp; push @words, /(\S+)/g } print @words . " words\n"; my $alpha = '[a-zA-Z]'; my $alnum = '[a-zA-Z0-9]'; my $qr = qr/^$alpha$alnum+$/; timethese(100, { '/^$alpha$alnum+$/ ' => \&testsub, '/^$alpha$alnum+$/o' => \&testsubo, '/$qr/ ' => \&testsubqr1, '$qr ' => \&testsubqr2, '/$qr/o ' => \&testsubqro, }); sub testsub { foreach (@words) { $count++ if(/^$alpha$alnum+$/); } + } sub testsubo { foreach (@words) { $count++ if(/^$alpha$alnum+$/o); } + } sub testsubqr1 { foreach (@words) { $count++ if(/$qr/); } + } sub testsubqr2 { foreach (@words) { $count++ if($_ =~ $qr); } + } sub testsubqro { foreach (@words) { $count++ if(/$qr/o); } + }

This is probably a fairer test than the original (less iterations of more data) and the output looks like this:

/^$alpha$alnum+$/ : 20 wallclock secs (20.41 usr + 0.00 sys = 20.41 C +PU) @ 4.90/s (n=100) /^$alpha$alnum+$/o: 9 wallclock secs ( 8.34 usr + 0.00 sys = 8.34 C +PU) @ 11.99/s (n=100) /$qr/ : 9 wallclock secs ( 9.59 usr + 0.00 sys = 9.59 C +PU) @ 10.43/s (n=100) $qr : 10 wallclock secs ( 9.94 usr + 0.00 sys = 9.94 C +PU) @ 10.06/s (n=100) /$qr/o : 9 wallclock secs ( 8.34 usr + 0.01 sys = 8.35 C +PU) @ 11.98/s (n=100)

The reason I used /$qr/ rather than =~ $qr was not because I didn't know how to use it, but because I was using it in an if statement and $qr being a reference would simply evaluate to true without even attempting a match. The results above appear to show that plain $qr is slightly slower than /$qr/ but that is almost certainly due to the fact that I had to spell it out as $_ =~ $qr and so the difference should be disregarded.

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Re: Re: Re^2: Never (qr//)
by BrowserUk (Pope) on May 14, 2003 at 10:32 UTC

    There is also the problem with using the =~ $qr form that you cannot use it if you need to apply the /g option.

    Nor if you have a regex that you sometimes want to use with capturing and sometimes without.

    Nor can you use it in substitutions.


    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller

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