[Gretl-users] psdroot() questions

Hi, I'm using the psdroot() (generalized Choleski) for the first time "seriously" and have some questions. - In one case there is an eigenvalue -1.2906e-006 in the input matrix, but psdroot still goes to work. So I guess there is no check on whether the matrix is actually PSD? - In another case I have an eigenvalue 3.6950e-016 (so zero apart from machine precision). There psdroot() produces a 'nan' output for one element and gretl spits out a warning. But since psdroot does exist exactly for the case of zero eigenvalues (otherwise one could use cholesky), why does that happen? Any hints/ideas? It's not so easy to post these examples because the printed precision is not enough to differentiate the cases. Thanks, sven