> Phil, please see the perlfunc entry for "pos" and the perlre section
> on \G. This is what you need.
Thanks a lot! I know about pos but thought it was read-only.
And \G is relatively new, isn't it? Certainly wasn't
existing in '97 when I learned perl :-)
And the "basics" are seldom read again in the docs...
Thank you very much, although it's still 32% slower:
2505792 bytes to do ...
Benchmark: timing 1000000 iterations of from_start, pos, re_dyn, re_once, substr,
substr_set...
from_start: 2 wallclock secs ( 1.06 usr + 0.00 sys = 1.06 CPU) @ 943396.23/s
(n=1000000)
pos: 0 wallclock secs ( 1.55 usr + 0.01 sys = 1.56 CPU) @ 641025.64/s
(n=1000000)
re_dyn: 7 wallclock secs ( 6.13 usr + 0.00 sys = 6.13 CPU) @ 163132.14/s
(n=1000000)
re_once: 2 wallclock secs ( 1.22 usr + 0.00 sys = 1.22 CPU) @ 819672.13/s
(n=1000000)
substr: 2 wallclock secs ( 2.39 usr + 0.01 sys = 2.40 CPU) @ 416666.67/s
(n=1000000)
substr_set: 3 wallclock secs ( 3.10 usr + 0.00 sys = 3.10 CPU) @ 322580.65/s
(n=1000000)
Rate re_dyn substr_set substr pos re_once from_start
re_dyn 163132/s -- -49% -61% -75% -80% -83%
substr_set 322581/s 98% -- -23% -50% -61% -66%
substr 416667/s 155% 29% -- -35% -49% -56%
pos 641026/s 293% 99% 54% -- -22% -32%
re_once 819672/s 402% 154% 97% 28% -- -13%
from_start 943396/s 478% 192% 126% 47% 15% --
Regards,
Phil
#!/usr/bin/perl
use Benchmark qw(cmpthese);
$pos=500;
$runs=1000000;
$_=`cat /etc/* 2> /dev/null`;
study $_;
print length($_), " bytes to do ...\n";
cmpthese($runs,
{
"from_start" => sub { m/\S*\s+(\S+)/; },
"re_dyn" => sub { m/^[\x00-\xff]{$pos}\S*\s+(\S+)/; },
"re_once" => sub { m/^[\x00-\xff]{$pos}\S*\s+(\S+)/o; },
"substr" => sub { substr($_,$pos) =~ m/\S*\s+(\S+)/; },
"substr_set" => sub { $tmp=substr($_,$pos); $tmp =~ m/\S*\s+(\S+)/; },
"pos" => sub { pos($pos); m/\G\S*\s+(\S+)/; },
}
);
