if ( $dr4 < 0 ) {
                #pre-populate deletion array;
            	my @delarray = ( 0 .. $chntot + 1 );
            	@dlarray = shuffle @delarray;

                my $cndiea = 0;
                foreach my $del ( 0 .. $chntot ) {
                    if ( $aod[$del][$yb] eq 'd' ) {
                        $cndiea++;
                    }
                }
                my $cnr = $cndiea;
                foreach my $xd ( $cnr .. $incrsdel - 1 ) {
                    my $xda = $dlarray[$xd];
                    if ( $aod[$xda][$yb] eq 'a' ) {
                        $aod[$xda][$yb] = 'd';
                    }
                }
            }