comment on

spurperl,
I was suprised to see that unpack wasn't the fastest so I changed it just a bit.

my @arr = unpack('A8A8A8A8A8A8A8A8A8A8A8A8A8A8A8A8A8A8A8A8', $str);
[download]

Not only is that compatible with older perl's - it is now the fastest. I might play a bit more to see if I can get an even faster version but to be fair, that really should have been:

# No longer wins but is still faster than '(A8)*'
my @arr = unpack((join '', ('A8' x ($strlen / 8))), $str);
[download]

Update: I wanted to see what would happen if the benchmark focused more on the functions themselves by removing some of the intermediate calculations. Noticed also I changed x 20 to x 200.

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark 'cmpthese';

my $str = "abcdefgh12345678" x 2000;
my $strlen = length $str;
my $end = $strlen / 8 - 1;
my $fmt = join '', ('A8' x ($strlen / 8));
my @pos = map {$_ * 8} 0 .. $end;

cmpthese(-3, {
    'regex'      => sub { my @arr = $str =~ /(........)/g;},
    'split_grep' => sub { my @arr = grep $_, split /(.{8})/, $str;},
    'split_pos'  => sub { my @arr = split /(?(?{pos() % 8})(?!))/, $st
+r;},
    'substr_map' => sub { my @arr = map substr($str, $_, 8), @pos;},
    'substr_for' => sub { my @arr; push @arr, substr($str, $_, 8) for 
+@pos;},
    'unpack'     => sub { my @arr = unpack($fmt, $str);}
});
__DATA__
             Rate  split_pos split_grep substr_map     unpack substr_f
+or
split_pos  38.2/s         --       -28%       -54%       -57%       -7
+4%
split_grep 53.1/s        39%         --       -36%       -41%       -6
+4%
regex      77.4/s      110%        52%        --        -3%      -12% 
+      -46%
substr_map 82.3/s       115%        55%         --        -8%       -4
+5%
unpack     89.5/s       134%        69%         9%         --       -4
+0%
substr_for  149/s       291%       182%        81%        67%         
+--
[download]

Cheers - L~R

In reply to Re: Splitting a string to chunks by Limbic~Region
in thread Splitting a string to chunks by spurperl

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