my $str = shift || "17:43:33:21:23:19:27:6";
my @a1 = ();
my @a2 = ();
my @a = split /:/, $str;
while ( my ( $p, $ad ) = splice @a, 0, 2 ) {
    push @a1, map {$ad} (1..$p);
    push @a2, ($ad) x $p;
}

use Benchmark 'cmpthese';

print "Accessing element 0:\n";
cmpthese(-1, { made_by_map => sub { $a1[0]; },
               made_by_x   => sub { $a2[0]; } });

print "\nAccessing element 50:\n";
cmpthese(-1, { made_by_map => sub { $a1[50]; },
               made_by_x   => sub { $a2[50]; } });

print "\nAccessing element 99:\n";
cmpthese(-1, { made_by_map => sub { $a1[99]; },
               made_by_x   => sub { $a2[99]; } });

print "\nAccessing random element:\n";
cmpthese(-1, { made_by_map => sub { $a1[rand 100]; },
               made_by_x   => sub { $a2[rand 100]; } });
[download]

Accessing element 0:
                 Rate   made_by_x made_by_map
made_by_x   7554581/s          --        -11%
made_by_map 8479758/s         12%          --

Accessing element 50:
                 Rate   made_by_x made_by_map
made_by_x   7788171/s          --         -4%
made_by_map 8095273/s          4%          --

Accessing element 99:
                 Rate made_by_map   made_by_x
made_by_map 8058884/s          --         -9%
made_by_x   8882975/s         10%          --

Accessing random element:
                 Rate made_by_map   made_by_x
made_by_map 1724352/s          --         -2%
made_by_x   1758653/s          2%          --
[download]

However, the results for different initial strings aren't really making any sense - when I use a string of one hundred repetitions of "1:8", I get essentially opposite results: the x array is significantly faster at doing [0], (by ~ 20%) there's a tie for [50] and the map array wins big at doing [99] (by ~ 10%), and then map wins at the random index test.

So far so good, but when I use "100:8", I get the map array winning at [50] and [99] and only losing by 1% on [0], yet still losing the random element test by 2%.

Are all my results just noise? I think I should make this a new SoPW post.

--
@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/
[download]