O( M+N + SIGMA( 2^3+2^4+...+2^n>N) + SIGMA( 2^3+...+2^m >M ) + MIN(N,M) )
         memory for 1st hash         memory for 2nd hash       memory for 1 array*
## (*assuming you chose the smallest array to use with the 2hash/1 list method)

##</code><code>##

O( M+N + SIGMA( 2^3+2^4+...+2^n>N) + N + M) )
         memory for smallest hash    memory for the two arrays
## for the 1 hash/2 arrays method.

##</code><code>##

C:\test>unionIntersect.pl -N=1e6 -MAX=27
       s/iter barvin    roy    buk   buk2
barvin   8.58     --   -43%   -58%   -64%
roy      4.86    77%     --   -26%   -37%
buk      3.59   139%    35%     --   -15%
buk2     3.05   182%    60%    18%     --


##</code><code>##

C:\test>unionIntersect.pl -N=5e5 -MAX=27
       s/iter barvin    buk    roy   buk2
barvin   3.87     --   -28%   -40%   -50%
buk      2.80    39%     --   -17%   -30%
roy      2.33    66%    20%     --   -16%
buk2     1.95    98%    43%    19%     --

##</code><code>##

sub  buk2{
    my( $aRef, $bRef ) = @_;

    my( $aBits, $bBits );
    for( $aBits, $bBits ) {
        local $\;
        open my $ram, '>', \$_;
        seek $ram, $MAX-1, 0;
        print $ram chr(0);
        close $ram;
    }

    vec( $aBits, $_, 1 ) = 1 for @$aRef;
    vec( $bBits, $_, 1 ) = 1 for @$bRef;

    my $iCount = unpack '%32b*', ( $aBits & $bBits );
    my $uCount = @$aRef + @$bRef - $iCount;

    $aBits = $bBits = '';

    print 'buk2: ', $iCount, ' : ', $uCount if $SHOW;
    return( $iCount, $uCount );
}