on settings* in a structure (different from defaults); 
%   if empty or not present, defaults will be used. Can be changed even
%   after initialization. 
%
%   penm.opts=[];
% 
% *Define decision variables* 
%
% * *number of (ordinary) decision variables*
%  If the field is not present, |Nx=0|; lower/upper bounds for box
%  constraints will be ignored. 
%
%   penm.Nx = 7; 
%
% * *number of matrix variables*, should be the same as |length(Y)|.
% If the field is not present, |NY=0|; thus |Y{:}