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