 * a numerically stable method to calculate z_{jk}  * currently slower than the old method but will be important for large sample size  * in principle, we can speed up for large n, but have not tried
 * a numerically stable method to calculate z_{jk}
 * currently slower than the old method but will be important for large sample size
 * in principle, we can speed up for large n, but have not tried


CosteaPaul/SamTools_custom,CosteaPaul/SamTools_custom,CosteaPaul/SamTools_custom,CosteaPaul/SamTools_custom