sub diff_gates ( $ $ $ )
{
    my ( $path, $g1, $g2 ) = @_;

    my %all_keys = ( %$g1, %$g2 );
    foreach my $key ( sort keys %all_keys )
    {
        if ( ! exists $g2->{$key} )
        {
            print "$path: g2 missing $key\n";
        }
        elsif ( ! exists $g1->{$key} )
        {
            print "$path: g1 missing $key\n";
        }
        elsif ( $g1->{$key} ne $g2->{$key} )
        {
            print "$path: $key diff between g1 and g2\n";
        }
    }
}