BrowserUk,
I have no idea how much additional memory Heap::Simple::XS uses under the covers, but the speed is dramatically faster than using splice with a binary search (above). 
#!/usr/bin/perl
use strict;
use warnings;
use Heap::Simple::XS;
use Time::HiRes qw/gettimeofday tv_interval/;

my $items = $ARGV[0] || 100;
my $str = 'a';
my %hash = map {$str++ => undef} 1 .. $items;
my $at_once = int($items * .10);

my $heap = Heap::Simple::XS->new(order => "gt", elements => "Scalar", 
+max_count => $at_once);
my ($cnt, $beg, %known) = ($at_once, [gettimeofday], ());
while (1) {
    while (my ($key, $val) = each %hash) {
        next if defined $val;
        if (exists $known{$key}) {
            $hash{$key} = $known{$key};
            next;
        }
        $heap->insert($key);
    }
    my $items = $heap->count;
    last if ! $items;
    %known = ();
    my $max = $cnt + $items;
    $known{$_} = $cnt-- for $heap->extract_all;
    $cnt = $max;
    $heap->clear;
}
my $elapsed = tv_interval($beg, [gettimeofday]);
my $per = sprintf("%.7f", $elapsed / $items);
print "Took $elapsed seconds for $items items ($per per item)\n";
__DATA__
C:\tmp>perl buk2.pl 100
Took 0.001999 seconds for 100 items (0.0000200 per item)

C:\tmp>perl buk2.pl 1000
Took 0.021015 seconds for 1000 items (0.0000210 per item)

C:\tmp>perl buk2.pl 10000
Took 0.241327 seconds for 10000 items (0.0000241 per item)

C:\tmp>perl buk2.pl 100000
Took 3.375 seconds for 100000 items (0.0000338 per item)

C:\tmp>perl buk2.pl 1000000
Took 48.25 seconds for 1000000 items (0.0000483 per item)

[download]

Cheers - L~R

In reply to Re^9: In-place sort with order assignment by Limbic~Region
in thread In-place sort with order assignment by BrowserUk

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