I am working on an optimization problem, maximum likelihood estimation. It is a complicated function. The message keep saying "user objective function returns complex; trying a new point". I do have a log(det(A)) in the log likelihood function. I guess that might be a problem. But I don't figure out how to improve this. My second question is the the "first order optimality" is huge, more than 1e3 or 1e4. Should I try more initial values or something else is wrong? Thanks.