class_docstr: Distribution of electrons on a sphere.
  
  Problem no 2 from COPS collection [2]_. Find
  the equilibrium state distribution (of minimal
  potential) of the electrons positioned on a
  conducting sphere.
  
  References
  ----------
  .. [1] E. D. Dolan, J. J. Mor'{e}, and T. S. Munson,
         "Benchmarking optimization software with COPS 3.0.",
          Argonne National Lab., Argonne, IL (US), 2004.
class_docstr_tok: ["Distribution","of","electrons","on","a","sphere",".","Problem","no","2","from","COPS","collection","[","2","]","_",".","Find","the","equilibrium","state","distribution","(","of","minimal","potential",")","of","the","electrons","positioned","on","a","conducting","sphere",".","References","--","--","--","--","--","..","[","1","]","E.","D.","Dolan",",","J.","J.","Mor","'","{","e","}",",","and","T.","S.","Munson",",","``","Benchmarking","optimization","software","with","COPS","3.0",".","``",",","Argonne","National","Lab.",",","Argonne",",","IL","(","US",")",",","2004","."]
code: def fun(self, x):
      dx, dy, dz = self._compute_coordinate_deltas(x)
      with np.errstate(divide="ignore"):
          dm1 = (dx**2 + dy**2 + dz**2) ** -0.5
      dm1[np.diag_indices_from(dm1)] = 0
      return 0.5 * np.sum(dm1)
  
imports: from __future__ import division, print_function, absolute_import
  import numpy
  import pytest
  from scipy.linalg import block_diag
  from scipy.sparse import csc_matrix
  from numpy.testing import TestCase, assert_array_almost_equal, assert_array_less, assert_allclose, assert_
  from pytest import raises
  from scipy.optimize import NonlinearConstraint, LinearConstraint, Bounds, minimize, BFGS, SR1
  from scipy._lib._numpy_compat import suppress_warnings
label_desc: Use image node_id 4 for calling the Elec obj's underlying member method code with example usage: obj.fun(x) and returns: unknown