ian of the objective as a (possibly sparse) matrix |ddf| 
%   of dimensions |(Nx+NYnnz) x (Nx+NYnnz)| or empty matrix |[]|.
% 
% The following lines specify the signature of the callbacks to evaluate
% |NgNLN + NgLIN| (function) constraints, if present. If |NgNLN = NgLIN = 0|,
% these will not be referenced.
%
%     function [g,    userdata] = confun(x,Y,userdata) 
%     function [dg,   userdata] = congrad(x,Y,userdata) 
%     function [ddgk, userdata] = conhess(x,Y,k,userdata)
% 
% They should r