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

sub randNbits {  pack 'C*', map rand(256), 1 .. ( shift() / 8 )}

our $TARGET //= 0.75; # 75% match
our $RECS //= 1e6;
our $BITS //= 1024;

my @recs;
$recs[ $_ ] = randNbits( $BITS ) for 0 .. $RECS-1;

my $select = randNbits( $BITS );
my $count = 0;
my $start = time;

for my $rec ( @recs ) {
    my $score = unpack( '%32b*', $select & $rec ) / $BITS;
    ++$count if $score >= $TARGET;
}

printf "Comparing $RECS records on $BITS attributes to discover $count matches took: %.9f s/rec\n",
    ( time() - $start ) / $RECS;