regex - 字符类与 "shorthand"类的性能

Question

在回答另一个问题时，有人提出，显式字符类( [0-9] )和“速记”类( \d )在性能方面可能存在差异。我最初的 react 是，如果根本存在差异，则可以忽略不计，但我没有(也找不到)有关它的任何信息，也没有弄清楚如何对此进行测试。

同样，[^0-9] 之间是否存在不可忽略的差异？ , [^\d]和 \D ?

Answer 1

如有疑问，基准!

我在 Perl 中对一个简单的正则表达式比较进行了基准测试。我发现 \d+确实更快。天啊。

use strict; use warnings;
use Benchmark qw(:all);
use feature "switch";

my $r1='\d+';
my $r2='[0-9]+';
my $r3='[[:digit:]]+';

sub test {
    my @lines = <DATA>;
    $_=shift;
    my $RegEx=(caller(0))[3];
    given($_) {
        when(1) { $RegEx=$r1; }
        when(2) { $RegEx=$r2; }
        when(3) { $RegEx=$r3; }
        default { die "$RegEx can't deal with $_\n"; }
    }   
    my $ln;
    my $total;
    my @numbers;
    foreach my $line (@lines) {
        $total=0;
        @numbers=$line=~/($RegEx)/g;
        $total+=$_ for (@numbers) ;
        $ln=$numbers[$#numbers];
        $total-=$ln;
        if ($ln != $total) {
            print "Bad RegEx result: Last Num != total in line!\n";
            print "Total=$total, ln=$ln, line:$line";
            die;
        }       
    }   
}

cmpthese(-10, {$r1=>'test(1)', $r2=>'test(2)', $r3=>'test(3)'});


__DATA__
Clip clap clock 1 mouse ran up the clock with 3 hands. The total here is 4.
The mouse with 2 ears followed. The total here is 2.
After that, the 6 wiskered mouse did dances with 14 second timing. 20.
It is hard to make up 5 lines with 2 or 3 numbers in each line. 10.
You start thinking about nurserey rhymes with 1 o 2 or 3 number. 6.
1 12 13 123 23 13 55 66 21 45 1 373

我在使用 Perl 5.10 64 位的 OS X 上得到以下结果:

                 Rate [[:digit:]]+       [0-9]+          \d+
[[:digit:]]+ 200781/s           --          -1%          -2%
[0-9]+       202831/s           1%           --          -1%
\d+          204605/s           2%           1%           --

Ubuntu 10.04 和 Perl 5.10.1 上的以下内容:

                 Rate [[:digit:]]+       [0-9]+          \d+
[[:digit:]]+ 264412/s           --          -3%          -6%
[0-9]+       273202/s           3%           --          -3%
\d+          280541/s           6%           3%           --