#! perl -slw
use strict;
use Time::HiRes qw[ time ];
use Devel::Size qw[ total_size ];

my %db;
for my $ac ( 100 ..999 ) {
    $db{ $ac }{ $_ } = '1234' for 100 .. 4999;
}

print "Total size in ram: ", total_size( \%db );

my $start = time;
for ( 1 .. 1e6 ) {
    my $info = $db{ 100+int(rand 800) }{ 100+int(rand 4900) };
}
printf "1e6 lookups took %.3f\n", time() - $start;

my $ram = chr(0) x 6.5e7;
open RAM, '+<', \$ram;
seek RAM, 0, 0;

for my $ac ( 100 .. 999 ) {
    for my $pre ( 100 .. 4999 ) {
        printf RAM "$ac,$pre, $db{ $ac }{ $pre }\n";
    }
}

print "size on disk (excluding blocking): ", length $ram;
seek RAM, 0, 0;

$start = time;

my %db2;
m[([^,]+),([^,]+),([^,]+)] and $db{ $1 }{ $2 } = $3 while <RAM>;

printf "Time to construct hash from csv (ram) file: %.3f\n", time()-$start;

__END__
C:\test>826814
Total size in ram: 15132924
1e6 lookups took 1.619
size on disk (excluding blocking): 65340000
Time to construct hash from (ram) file: 14.578