title: gradient at the minimum in fmin_l_bfgs_b
body: <p>I am using fmin_l_bfgs_b for a bounded minimization on 4 parameters. 
  I would like to inspect the gradient at the minimum of the cost function and for this I call the d['grad'] parameter as described in the documentation of fmin_l_bfgs_b. My problem is that d['grad'] is an array of size 4 looking like:</p>
  
  <p>'grad': array([  8.38440428e-05,  -5.72697445e-04,   3.21875859e-03,
          -2.21115926e+00])</p>
  
  <p>I would expect it to be a single value close to zero. Does this have something to do with the number of the parameters I am using for the minimization (4)..? Not what I would expect but  any help would be appreciated.</p>