Re^2: Surprisingly poor regex performance

What about m/(?:\A|\n)(.*$pat.*\n)/omg?

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Comment on Re^2: Surprisingly poor regex performance Download Code

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Re^3: Surprisingly poor regex performance by Joost (Canon) on Dec 13, 2004 at 17:01 UTC
Good stuff.. It's faster :-) #!/usr/local/bin/perl -w use strict; use Benchmark; my $pat = 'foo'; $/=undef; open F,"<","/usr/share/dict/words"; my $mmap = <F>; close F; timethese( 100, { # 'orig' => sub { # while ($mmap =~ m/^([^\n]$pat[^\n]\n)/omg) { # warn $1; # } # }, 'fast' => sub { while ($mmap =~ m/\n?(.$pat.\n)/omg) { warn $1; } }, 'better' => sub { while ($mmap =~ m/(?:\A\|\n)(.$pat.\n)/omg) { warn $1; } }, } ) __END__ Benchmark: timing 100 iterations of better, fast... better: 26 wallclock secs (23.13 usr + 0.06 sys = 23.19 CPU) @ 4 +.31/s (n=100) fast: 41 wallclock secs (39.73 usr + 0.09 sys = 39.82 CPU) @ 2 +.51/s (n=100) [download] (original takes about 25 seconds per iteration on my machine) "What should it profit a man, if he should win a flame war, yet lose his cool?"*	[reply] [d/l]

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Re^3: Surprisingly poor regex performance
by Joost (Canon) on Dec 13, 2004 at 17:01 UTC

#!/usr/local/bin/perl -w
use strict;
use Benchmark;

my $pat = 'foo';

$/=undef;
open F,"<","/usr/share/dict/words";
my $mmap = <F>;
close F;


timethese( 100, {
# 'orig' => sub {
#        while ($mmap =~ m/^([^\n]*$pat[^\n]\n)/omg) {
#            warn $1;
#        }
# },
 'fast' => sub {
         while ($mmap =~ m/\n?(.*$pat.*\n)/omg) {
             warn $1;
        }
 },
 'better' => sub {
     while ($mmap =~ m/(?:\A|\n)(.*$pat.*\n)/omg) {
         warn $1;
     }
 },
}
)
__END__
Benchmark: timing 100 iterations of better, fast...
    better: 26 wallclock secs (23.13 usr +  0.06 sys = 23.19 CPU) @  4
+.31/s (n=100)
      fast: 41 wallclock secs (39.73 usr +  0.09 sys = 39.82 CPU) @  2
+.51/s (n=100)
[download]

"What should it profit a man, if he should win a flame war, yet lose his cool?"

[reply]
[d/l]