Update: Replaced bit-OR with addition to have $x and $y line up for better readability.

This post is a fun study, comparing pack 'i2' against the mapping of two integers into one via bit manipulation. A use case for doing this is wanting readable keys for storing into a database using one field. This laptop runs an i7 Haswell at 2.6 GHz. Unfortunately, I do not have anything slower to run on.

bin/perl v5.26.0

$ perl createblinker.pl 500000 -900000 100 >x.tmp 2>y.tmp

$ /opt/perl-5.26.0/bin/perl -I. tbench1.pl x.tmp 2      # pack i2
cell count at start = 1500000
run benchmark for 2 ticks
cell count at end = 1500000
time taken: 37 secs
time taken: 58 secs  <- 32-bit Windows VM

$ /opt/perl-5.26.0/bin/perl -I. tbench1.pl x.tmp 2      # mapping
cell count at start = 1500000
run benchmark for 2 ticks
cell count at end = 1500000
time taken: 39 secs
time taken: 64 secs  <- 32-bit Windows VM, applied 32-bit tip below
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bin/cperl v5.24.3c

$ /opt/cperl-5.24.3c/bin/cperl -I. tbench1.pl x.tmp 2   # pack i2
cell count at start = 1500000
run benchmark for 2 ticks
cell count at end = 1500000
time taken: 37 secs

$ /opt/cperl-5.24.3c/bin/cperl -I. tbench1.pl x.tmp 2   # mapping
cell count at start = 1500000
run benchmark for 2 ticks
cell count at end = 1500000
time taken: 38 secs
[download]

I used tybalt89's update and applied the mapping logic. All tests pass, thanks to new test script by eyepopslikeamosquito. Please ensure Perl is compiled with 64-bit support. 16 bits hold the value for $y and 2 bits for whether $x,$y are less than 0. $x is stored in the remaining bits. This results in minimum key lenght as $y isn't big. Though, adjust accordingly the number of bits to shift and bitmask if necessary.

bits 63-18 contains the $x value
bits 17-2  contains the $y value
bit  1     set when $y < 0
bit  0     set when $x < 0
[download]

On 32-bit hardware, replace 18 and 0xFFFF with 10 and 0xFF throughout the module.

bits 31-10 contains the $x value
bits 9-2   contains the $y value
bit  1     set when $y < 0
bit  0     set when $x < 0
[download]

Both _unpack and _pack are inlined inside tick for maximum performance.

package Organism;

use strict;
# use warnings;

sub _pack {
   my ( $x, $y ) = @_;
   # bits 0,1 negative flag for $x,$y respectively
   return
      ( abs($x) << 18 ) + ( $x < 0 ? 1 : 0 ) +
      ( abs($y) << 2  ) + ( $y < 0 ? 2 : 0 );
}

sub _unpack {
   my ( $n ) = @_;
   # bits 0,1 negative flag for $x,$y respectively
   return (
      $n & 0x1 ? -($n >> 18        ) : $n >> 18,
      $n & 0x2 ? -($n >> 2 & 0xFFFF) : $n >> 2 & 0xFFFF
   );
}

sub count {
   return scalar keys %{ shift->{Cells} };
}

# Input a list of [ x, y ] coords
sub insert_cells {
   my $cells = shift->{Cells};
   for my $r (@_) { $cells->{ _pack @{$r} } = undef }
}

# Return sorted list of cells in the Organism.
# Used for verification and testing the state of the organism.
sub get_live_cells {
   sort { $a->[0] <=> $b->[0] || $a->[1] <=> $b->[1] }
      map { [ _unpack $_ ] }
      keys %{ shift->{Cells} };
}

sub tick {
   my $self  = shift;
   my $cells = $self->{Cells};
   my ( $k1, $k2, $k3, $k4, $k5, $k6, $k7, $k8,
        $x0, $x1, $x2, $y0, $y1, $y2, %new_cells, %dead_cells );

   for my $c (keys %{ $cells }) {
      # Get the (up to 8) dead cells surrounding the cell
      ( $x0, $y0 ) = (
         $c & 0x1 ? -($c >> 18        ) : $c >> 18,
         $c & 0x2 ? -($c >> 2 & 0xFFFF) : $c >> 2 & 0xFFFF
      );

      ( $x1, $x2, $y1, $y2 ) = ( $x0 - 1, $x0 + 1, $y0 - 1, $y0 + 1 );

      $dead_cells{$_}++ for my @zcells = (
         ( $k1 = ( abs($x1) << 18 ) + ( $x1 < 0 ? 1 : 0 ) +
                 ( abs($y1) << 2  ) + ( $y1 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k1}),

         ( $k2 = ( abs($x1) << 18 ) + ( $x1 < 0 ? 1 : 0 ) +
                 ( abs($y0) << 2  ) + ( $y0 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k2}),

         ( $k3 = ( abs($x1) << 18 ) + ( $x1 < 0 ? 1 : 0 ) +
                 ( abs($y2) << 2  ) + ( $y2 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k3}),

         ( $k4 = ( abs($x0) << 18 ) + ( $x0 < 0 ? 1 : 0 ) +
                 ( abs($y1) << 2  ) + ( $y1 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k4}),

         ( $k5 = ( abs($x0) << 18 ) + ( $x0 < 0 ? 1 : 0 ) +
                 ( abs($y2) << 2  ) + ( $y2 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k5}),

         ( $k6 = ( abs($x2) << 18 ) + ( $x2 < 0 ? 1 : 0 ) +
                 ( abs($y1) << 2  ) + ( $y1 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k6}),

         ( $k7 = ( abs($x2) << 18 ) + ( $x2 < 0 ? 1 : 0 ) +
                 ( abs($y0) << 2  ) + ( $y0 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k7}),

         ( $k8 = ( abs($x2) << 18 ) + ( $x2 < 0 ? 1 : 0 ) +
                 ( abs($y2) << 2  ) + ( $y2 < 0 ? 2 : 0 )
         ) x !(exists $cells->{$k8})
      );

      # Check the live cell
      # Note: next line equivalent to nlive == 2 || nlive == 3
      @zcells == 5 || @zcells == 6 and $new_cells{$c} = undef;
   }

   $dead_cells{$_} == 3 and $new_cells{$_} = undef for keys %dead_cell
+s;
   $self->{Cells} = \%new_cells;
}

sub new {
   my $class = shift;
   my %init_self = ( Cells => {} );
   bless \%init_self, $class;
}

1;
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Pack is faster, of course. However, mapping two integers into one is not far behind.

Regards, Mario