Make Problem.bounds updateable after instantiation.

opty/direct_collocation.py

@@ -130,6 +130,16 @@ class Problem(cyipopt.Problem):
                       eomM2, ... eomMN,
                       c1, ..., co]
 
+    The ``bounds`` attribute may be changed to a new dictionary after
+    instantiation of ``Problem`` by setting ``Problem.bounds = {..}`` but
+    changing ``problem.bounds[state] = (low, high)`` will have no effect.
+
+    Some attributes are only accessible from the
+    :py:class:`ConstraintCollocator` object associated with this ``Problem``
+    and may be accessed as follows::
+
+       Problem_instance.collocator.name_of_attribute
+
     """
 
     INF = 10e19
@@ -437,8 +447,20 @@ def _generate_bound_arrays(self):
                     msg = 'Bound variable {} not present in free variables.'
                     raise ValueError(msg.format(var))
 
-        self.lower_bound = lb
-        self.upper_bound = ub
+        # NOTE : The lower and upper bounds arrays are passed into Problem and
+        # pointers to the data in the arrays are stored in the underlying Ipopt
+        # problem object. So if they already exist and the user modifies them
+        # by creating a new Problem.bounds dictionary update the data instead
+        # of created new arrays.
+        if hasattr(self, '_lower_bound'):
+            self._lower_bound[:] = lb
+        else:
+            self._lower_bound = lb
+
+        if hasattr(self, 'upper_bound'):
+            self._upper_bound[:] = ub
+        else:
+            self._upper_bound = ub
 
     def objective(self, free):
         """Returns the value of the objective function given a solution to the

opty/tests/test_direct_collocation.py

@@ -400,6 +400,14 @@ def test_pendulum():
 
     assert prob.collocator.num_instance_constraints == 4
 
+    # NOTE : you cannot set the bounds directly, it has to be done via setting
+    # the Problem.bounds to a new dictionary.
+    with raises(AttributeError):
+        prob.lower_bound = np.ones(prob.num_free)
+
+    with raises(AttributeError):
+        prob.upper_bound = np.ones(prob.num_free)
+
     expected_low_con_bounds = np.zeros(prob.num_constraints)
     expected_low_con_bounds[:50] = -20.0
     expected_low_con_bounds[50:100] = -10.0
@@ -470,6 +478,31 @@ def test_problem(self):
 
         assert prob.collocator.num_instance_constraints == 0
 
+        lb = prob.lower_bound
+        ub = prob.upper_bound
+
+        assert prob.collocator.num_instance_constraints == 0
+
+        prob.bounds = {
+            x: (-12.0, 12.0),
+            f: (-8.0, 8.0),
+            m: (-1.0, 1.0),
+            c: (-0.5, 0.5),
+        }
+
+        expected_lower = np.array([-12.0, -12.0,
+                                  -INF, -INF,
+                                  -8.0, -8.0,
+                                  -0.5, -INF, -1.0])
+        np.testing.assert_allclose(prob.lower_bound, expected_lower)
+        assert np.shares_memory(lb, prob.lower_bound)
+        expected_upper = np.array([12.0, 12.0,
+                                   INF, INF,
+                                   8.0, 8.0,
+                                   0.5, INF, 1.0])
+        np.testing.assert_allclose(prob.upper_bound, expected_upper)
+        assert np.shares_memory(ub, prob.upper_bound)
+
         # run Problem again to see if the cache worked.
         prob = Problem(
             lambda x: 1.0,