Re: How foreach loops decide what to iterate through

[Lawliet]

in reply to How foreach loops decide what to iterate through

Welcome to The Monastery, and thank you for writing your node.

I have little experience with the Benchmark module, but after conducting some tests, I would say that you should use the latter method, the one you prefer. It is more concise, easier to read, and a little more efficient. (thanks for the notice, ikegami.)

#!/usr/bin/perl

use warnings;
use strict;
use 5.010;
use Benchmark qw(:all);
use Data::Dumper;

cmpthese(100000, {
    'LowOutside' => sub {
        my @array = qw(8 1 3 5 6 2);
        @array = sort @array;
        foreach (@array) {
            my $num = $_;
        }
    },
    
    'LowInside' => sub {
        my @array = qw(8 1 3 5 6 2);
        foreach (sort @array) {
            my $num = $_;
        }
    },
    
    'Outside' => sub {
        my @array = qw(8 1 3 5 6 2) x 100;
        @array = sort @array;
        foreach (@array) {
            my $num = $_;
        }
    },
    
    'Inside' => sub {
        my @array = qw(8 1 3 5 6 2) x 100;
        foreach (sort @array) {
            my $num = $_;
        }
    }
});

__END__
               Rate    Outside     Inside LowOutside  LowInside
Outside      1681/s         --        -1%       -99%       -99%
Inside       1691/s         1%         --       -99%       -99%
LowOutside 169492/s      9985%      9924%         --        -5%
LowInside  178571/s     10525%     10461%         5%         --

[ikegami]

I would say that you should use the latter method, the one you prefer. It is more concise, easier to read, and a little more efficient.

1% and even 5% is within the margin or error of Benchmark, so that last phrase is inaccurate.

I'm actually surprised they're the same speed. @a = sort @a; is optimized to be done in place, and I think for (@a) is optimized over the more general for (LIST) (it's definitely implemented differently).