title: what is optimality in scipy.least_squares
body: <p>Hello I have a quick question concerning the terminology used in <a href="https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.least_squares.html" rel="nofollow noreferrer">https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.least_squares.html</a> .<br>
  They define optimality : float</p>
  
  <p>First-order optimality measure. In unconstrained problems, it is always the uniform norm of the gradient. In constrained problems, it is the quantity which was compared with gtol during iterations.</p>
  
  <p>Is this what I have gotten to know as reduced chi square = (chi^2/DoF)?</p>