Jeff Pang wrote:
hi,lists,
I have two perl scripts as following:
a.pl:
----
#!/usr/bin/perl
use strict;
my @logs = glob "~/logs/rcptstat/da2005_12_28/da.127.0.0.1.*";
foreach my $log (@logs) {
open (HD,$log) or die "$!";
while(<HD>){
if (
($_ =~ /×¢²á/o) ||
($_ =~ /Õ÷ÎÄ/o) ||
($_ =~ /Ê¥µ®¿ìÀÖ/) ||
($_ =~ /ӦƸ/o) ||
($_ =~ /�ø�¨/o) ||
($_ =~ /·¢»õ/o) ||
($_ =~ /±±¾©/o) ||
($_ =~ /×Ê��/o) ||
($_ =~ /�Å�¢/o) ||
($_ =~ /�ãɽ/o) ||
($_ =~ /°Ù�ò/o) ||
($_ =~ /Ãâ·Ñ/o) ) {
print $_;
}
}
close HD;
}
b.pl
----
#!/usr/bin/perl
use strict;
my $ref = sub { $_[0] =~ /×¢²á/o || $_[0] =~ /Õ÷ÎÄ/o || $_[0] =~
/Ê¥µ®¿ìÀÖ/o ||
$_[0] =~ /ӦƸ/o || $_[0] =~ /�ø�¨/o || $_[0] =~
/·¢»õ/o ||
$_[0] =~ /±±¾©/o || $_[0] =~ /×Ê��/o || $_[0] =~
/�Å�¢/o ||
$_[0] =~ /�ãɽ/o || $_[0] =~ /°Ù�ò/o || $_[0] =~
/Ãâ·Ñ/o };
my @logs = glob "~/logs/rcptstat/da2005_12_28/da.127.0.0.1.*";
foreach my $log (@logs) {
open (HD,$log) or die "$!";
while(<HD>){
print if $ref->($_);
}
close HD;
}
I run the 'time' command to get the running speed:
time perl a.pl > /dev/null
real 0m0.190s
user 0m0.181s
sys 0m0.008s
time perl b.pl > /dev/null
real 0m0.286s
user 0m0.278s
sys 0m0.007s
Why the a.pl is faster than b.pl? I think ever the resulte should be
opposite.Thanks.
Well, the time differences aren't dramatic. But off hand, I would say
that a.pl is faster because no subroutine call is involved.
A couple of other observations:
1. /o is useless on these regexes, since they don't interpolate any
variables.
2. $_ is the default target for the m// operator, so
$_ =~ /regex/
can be replaced with simply
/regex/
3. It will probably be faster to use a single regex of the format:
/pata|patb|patc|patd/
If the alternation can stay inside the regex code rather than happening
out at the Perl opcode level, it might be faster.
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