Update: Added SQLite_File for comparison.

Hello talexb,

The following is a demonstration comparing a plain hash against CDB_File, DB_File. and SQLite_File.

use strict;
use warnings;
use feature 'state';

use CDB_File;
use DB_File;
use SQLite_File;
use Time::HiRes 'time';

my @points = (
   [  0,  0 ],
   [ -1, -2 ],
   [  1,  2 ],
   [ -1,  2 ],
   ...
);

sub plain_hash {
   my %hash;
   $hash{ join(':',@{$_}) } = 1 for @points;
   \%hash;
}

sub cdb_hash {
   my %hash;

   # create CDB file
   my $cdb = CDB_File->new("t.cdb", "t.cdb.$$")
      or die "$!\n";
   $cdb->insert( join(':',@{$_}), 1 ) for @points;
   $cdb->finish;

   # use CDB file
   tie %hash, 'CDB_File', "t.cdb" or die "$!\n";
   \%hash;
}

sub db_hash {
   my %hash;

   # create DB file
   tie %hash, 'DB_File', "t.db", O_CREAT|O_RDWR, $DB_BTREE;
   $hash{ join(':',@{$_}) } = 1 for @points;
   untie %hash;

   # use DB file
   tie %hash, 'DB_File', "t.db", O_RDWR, $DB_BTREE;
   \%hash;
}

sub sql_hash {
   tie my %hash, 'SQLite_File', "sql.db";
   $hash{ join(':',@{$_}) } = 1 for @points;
   \%hash;
}

sub look {
   my $cells = shift;
   state $points_str = [ map { join(':',@{$_}) } @points ];
   for my $p (@{ $points_str }) {
      exists $cells->{$p} or die;
   }
}

sub bench {
   my ( $desc, $func   ) = @_;
   my ( $cells, $iters ) = ( $func->(), 50000 );

   my $start = time;
   look($cells) for 1..$iters;
   my $elapse = time - $start;

   printf "%s duration : %0.03f secs\n", $desc, $elapse;
   printf "%s lookups  : %d / sec\n",
      $desc, @points * $iters / $elapse;
}

bench( "plain", \&plain_hash );
bench( "  cdb", \&cdb_hash   );
bench( "   db", \&db_hash    );
bench( "  sql", \&sql_hash   );
[download]

Results: The native Perl on Mac OS X 10.11.6 is v5.18.2. The hardware is a Haswell i7 chip at 2.6 GHz.

Regarding CDB_File and DB_File performance, these run better with Perl 5.20 and later releases.

$ perl test.pl
plain duration : 0.639 secs
plain lookups  : 10243321 / sec
  cdb duration : 5.692 secs
  cdb lookups  : 1150711 / sec
   db duration : 9.746 secs
   db lookups  : 672046 / sec

$ /opt/perl-5.26.0/bin/perl test.pl
plain duration : 0.517 secs
plain lookups  : 12677776 / sec
  cdb duration : 3.881 secs
  cdb lookups  : 1687545 / sec
   db duration : 6.134 secs
   db lookups  : 1067780 / sec
  sql duration : 184.338 secs
  sql lookups  : 35532 / sec
[download]

Regards, Mario