Fixed #750 for the DOcplex translator

CHANGELOG.md

@@ -48,6 +48,7 @@ Fixed
 
 -   Boolean logic circuit construction (#819)
 -   Measurement on actual devices for Amplitude Estimation algorithms (#841) (#842)
+-   Supported constant values on the left-hand side of constraints and variables on the right-hand side of constraints for the DOcplex translator (#750)
 
 [0.6.5](https://github.com/Qiskit/qiskit-aqua/compare/0.6.4...0.6.5) - 2020-03-16
 =================================================================================

qiskit/optimization/ising/docplex.py

@@ -160,13 +160,13 @@ def get_operator(mdl: Model, auto_penalty: bool = True,
 
     # convert constraints into penalty terms.
     for constraint in mdl.iter_constraints():
-        constant = constraint.right_expr.get_constant()
+        constant = constraint.cplex_num_rhs()
 
         # constant parts of penalty*(Constant-func)**2: penalty*(Constant**2)
         shift += penalty * constant ** 2
 
         # linear parts of penalty*(Constant-func)**2: penalty*(-2*Constant*func)
-        for __l in constraint.left_expr.iter_terms():
+        for __l in constraint.iter_net_linear_coefs():
             z_p = np.zeros(num_nodes, dtype=np.bool)
             index = q_d[__l[0]]
             weight = __l[1]
@@ -176,8 +176,8 @@ def get_operator(mdl: Model, auto_penalty: bool = True,
             shift += -penalty * constant * weight
 
         # quadratic parts of penalty*(Constant-func)**2: penalty*(func**2)
-        for __l in constraint.left_expr.iter_terms():
-            for l_2 in constraint.left_expr.iter_terms():
+        for __l in constraint.iter_net_linear_coefs():
+            for l_2 in constraint.iter_net_linear_coefs():
                 index1 = q_d[__l[0]]
                 index2 = q_d[l_2[0]]
                 weight1 = __l[1]
@@ -258,8 +258,8 @@ def _auto_define_penalty(mdl: Model, default_penalty: float = 1e5) -> float:
     # if a constraint has float coefficient, return 1e5 for the penalty coefficient.
     terms = []
     for constraint in mdl.iter_constraints():
-        terms.append(constraint.right_expr.get_constant())
-        terms.extend(term[1] for term in constraint.left_expr.iter_terms())
+        terms.append(constraint.cplex_num_rhs())
+        terms.extend(term[1] for term in constraint.iter_net_linear_coefs())
     if any(isinstance(term, float) and not term.is_integer() for term in terms):
         logger.warning('Using %f for the penalty coefficient because a float coefficient exists '
                        'in constraints. \nThe value could be too small. '

test/optimization/test_docplex.py

@@ -320,3 +320,21 @@ def test_docplex_constant_and_quadratic_terms_in_object_function(self):
 
         # Compare objective
         self.assertEqual(result.eigenvalue.real + offset, expected_result)
+
+    def test_constants_in_left_side_and_variables_in_right_side(self):
+        """ Test Constant values on the left-hand side of constraints and
+        variables on the right-hand side of constraints for the DOcplex translator"""
+        mdl = Model('left_constants_and_right_variables')
+        x = mdl.binary_var(name='x')
+        y = mdl.binary_var(name='y')
+        mdl.maximize(mdl.sum(x + y))
+        mdl.add_constraint(x == y)
+
+        qubit_op, offset = docplex.get_operator(mdl)
+        print(qubit_op.print_details())
+        e_e = NumPyMinimumEigensolver(qubit_op)
+        result = e_e.run()
+
+        self.assertEqual(result['eigenvalue'] + offset, -2)
+        actual_sol = result['eigenstate'].tolist()
+        self.assertListEqual(actual_sol, [0, 0, 0, 1])