InputParameter in variable bounds

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 ## Bug fixes
 
+- Fixed a bug where variable bounds could not contain `InputParameters` ([#2795](https://github.com/pybamm-team/PyBaMM/pull/2795))
 - Improved `model.latexify()` to have a cleaner and more readable output ([#2764](https://github.com/pybamm-team/PyBaMM/pull/2764))
 - Fixed electrolyte conservation in the case of concentration-dependent transference number ([#2758](https://github.com/pybamm-team/PyBaMM/pull/2758))
 - Fixed `plot_voltage_components` so that the sum of overpotentials is now equal to the voltage ([#2740](https://github.com/pybamm-team/PyBaMM/pull/2740))

pybamm/discretisations/discretisation.py

@@ -297,9 +297,23 @@ def set_variable_slices(self, variables):
             # Add to slices
             y_slices[variable].append(slice(start, end))
             y_slices_explicit[variable].append(slice(start, end))
+
             # Add to bounds
-            lower_bounds.extend([variable.bounds[0].evaluate()] * (end - start))
-            upper_bounds.extend([variable.bounds[1].evaluate()] * (end - start))
+            def evaluate_bound(bound, side):
+                if bound.has_symbol_of_classes(pybamm.InputParameter):
+                    if side == "lower":
+                        return -np.inf
+                    elif side == "upper":
+                        return np.inf
+                else:
+                    return bound.evaluate()
+
+            lower_bounds.extend(
+                [evaluate_bound(variable.bounds[0], "lower")] * (end - start)
+            )
+            upper_bounds.extend(
+                [evaluate_bound(variable.bounds[1], "upper")] * (end - start)
+            )
             # Increment start
             start = end
 

tests/unit/test_discretisations/test_discretisation.py

@@ -142,6 +142,14 @@ def test_discretise_slicing(self):
         with self.assertRaisesRegex(TypeError, "y_slices should be"):
             disc.y_slices = 1
 
+        # bounds with an InputParameter
+        a = pybamm.InputParameter("a")
+        b = pybamm.InputParameter("b")
+        v = pybamm.Variable("v", domain=whole_cell, bounds=(a, b))
+        disc.set_variable_slices([v])
+        np.testing.assert_array_equal(disc.bounds[0], [-np.inf] * 100)
+        np.testing.assert_array_equal(disc.bounds[1], [np.inf] * 100)
+
     def test_process_symbol_base(self):
         # create discretisation
         mesh = get_mesh_for_testing()