fminunc with quasi-Newton algorithm giving unexpected results

Why am I getting unexpected results and exitflag = 5 with "fminunc" quasi-Newton algorithm?

Answer 1

[MathWorks Support Team]

Double check that the "fminunc" function is correct. Small errors in the function to minimize could cause for very unexpected results.

Additionally, setting 'SpecifyObjectiveGradient' to true and defining a gradient function might drastically improve your solution.

Please see the following link for information on defining a gradient for the objective function:

https://www.mathworks.com/help/optim/ug/fminunc.html?searchHighlight=fminunc&s_tid=doc_srchtitle#butpb7p-options