5. Caching

Memoizing

Suppose you have a function that will take a long time to compute
Cache the results in a database
Run an overnight batch job to populate the database
In the morning, the function is fast
Perl's tie feature and the Memoize module make this easy:

        use DB_File;
        tie %h, 'DB_File', "cmyk.db", O_RDWR|O_CREAT, 0666 or die ...;

        use Memoize;
        memoize 'cmyk', SCALAR_CACHE => [ HASH => \%h ];

        for my $r (0 .. 255) {
          for my $g (0 .. 255) {
            for my $b (0 .. 255) {
              cmyk($r, $g, $b);
            }
          }
        }