|G|| <  min(0.5,sqrt(||G||))
%    'fixed'               ||R|| < CGTol
%                          where R is the residual and G is the gradient 
%                          of FUN at X
%
%  CGTol                   CG stopping tolerance when CGTolType is 
%                          'fixed' {1e-6}
%
%  HessVecFDStep           Hessian vector product finite difference step {1e-10}
%    0                     Use iterate-based step: 1e-8*(1+||X||)
%    >0                    Fixed value to use as the difference step