I was curious if storing the values in a hash in the first place might be better. Turns out, no, even if the output is a hash as well.

use warnings;
use strict;
use Benchmark qw/cmpthese/;

my @array = ( 'a'..'t' );
my %hash = map { $_ => $array[$_] } 0..$#array;
my $index = 3;
my $expect = 'abcefghijklmnopqrst';
use constant TEST => 0;

cmpthese(-2, {
    splice => sub {
        my @output = @array;
        splice @output, $index, 1;
        join("", @output) eq $expect or die if TEST;
    },
    hash_slice => sub {
        my %ha; @ha{0..$#array} = @array;
        delete $ha{$index};
        my @output = @ha{ sort {$a <=> $b} keys %ha };
        join("", @output) eq $expect or die if TEST;
    },
    swap => sub {
        my @output = @array;
        $output[$index] = pop @output;
        join("", sort @output) eq $expect or die if TEST;
    },
    prehash_del => sub {
        my %ha = %hash;
        delete $ha{$index};
        my @output = @ha{ sort {$a <=> $b} keys %ha };
        join("", @output) eq $expect or die if TEST;
    },
    prehash_local => sub {
        delete local $hash{$index};
        my @output = @hash{ sort {$a <=> $b} keys %hash };
        join("", @output) eq $expect or die if TEST;
    },
    prehash_grep => sub {
        my @output = @hash{ sort {$a <=> $b}
            grep { $_ != $index } keys %hash };
        join("", @output) eq $expect or die if TEST;
    },
    outhash => sub {
        my %output = %hash;
        delete $output{$index};
        join("", @output{ sort {$a <=> $b} keys %output }) eq $expect
            or die if TEST;
    },
});

__END__

                  Rate hash_slice prehash_del prehash_local prehash_gr
+ep outhash swap splice
hash_slice    127891/s         --        -10%          -40%         -5
+0%    -68% -85%   -85%
prehash_del   142822/s        12%          --          -33%         -4
+5%    -64% -83%   -84%
prehash_local 214633/s        68%         50%            --         -1
+7%    -46% -75%   -75%
prehash_grep  258191/s       102%         81%           20%           
+--    -36% -70%   -70%
outhash       400518/s       213%        180%           87%          5
+5%      -- -53%   -54%
swap          847448/s       563%        493%          295%         22
+8%    112%   --    -2%
splice        868423/s       579%        508%          305%         23
+6%    117%   2%     --

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In reply to Re^2: Fastest way to "pick without replacement" by haukex
in thread Fastest way to "pick without replacement" by haukex

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