use strict;
use warnings;
use Benchmark qw(timethese);

my $nb_elements = 2e6;
my @top3;

my @startArray;

push @startArray, ["", "", int rand (1e7)] for 1..$nb_elements;

sub discard_sort{ 
    my @masterArray = @startArray;
	my @top3 = sort {$b->[2] <=> $a->[2]} @masterArray[0..2];
	my $min_top = $top3[2][2];
	$nb_elements--;
	for my $sub_aref (@masterArray [3..$nb_elements]) {
		next if $sub_aref->[2] <= $min_top;
		@top3 =  (sort {$b->[2] <=> $a->[2]} $sub_aref, @top3)[0..2];
		$min_top = $top3[2][2];
	}
}

sub discard_manual{ 
    my @masterArray = @startArray;
	@top3 = sort {$b->[2] <=> $a->[2]} @masterArray[0..2];
	my $min_top = $top3[2][2];
	$nb_elements--;
	for my $sub_aref (@masterArray [3..$nb_elements]) {
		next if $sub_aref->[2] <= $min_top;
		if ($sub_aref->[2] > $top3[0][2]) {
			unshift @top3, $sub_aref;
			pop @top3;
		} 
		elsif ( $sub_aref->[2] > $top3[1][2]) {
			$top3[2] = $top3[1];
			$top3[1] = $sub_aref;
		} else {
			pop @top3;
			push @top3, $sub_aref;
		} 
		$min_top = $top3[2][2];
	}
}

sub sort_strategy {
	my @masterArray = @startArray;
	my @top3 = (sort {$b->[2] <=> $a->[2]} @masterArray)[0..2];
}

timethese (5, {  
	'walk once with sort' => \&discard_sort,
	'walk once manual insert' => \&discard_manual,
	'sort' => \&sort_strategy});

##</code><code>##

Benchmark: timing 5 iterations of sort, walk once manual insert, walk once with sort...
sort: 60 wallclock secs (60.37 usr +  0.02 sys = 60.39 CPU) @  0.08/s (n=5)
walk once manual insert:  3 wallclock secs ( 2.79 usr +  0.00 sys =  2.79 CPU) @  1.79/s (n=5)
walk once with sort:  3 wallclock secs ( 2.76 usr +  0.00 sys =  2.76 CPU) @  1.81/s (n=5)

##</code><code>##

Benchmark: timing 5 iterations of sort, walk once manual insert, walk once with sort...
sort: 170 wallclock secs (169.96 usr +  0.03 sys = 169.99 CPU) @  0.03/s (n=5)
walk once manual insert:  7 wallclock secs ( 6.90 usr +  0.03 sys =  6.93 CPU) @  0.72/s (n=5)
walk once with sort:  7 wallclock secs ( 6.86 usr +  0.00 sys =  6.86 CPU) @  0.73/s (n=5)