#692 adding features to base solver to allow external variables

pybamm/discretisations/discretisation.py

@@ -141,8 +141,17 @@ def process_model(self, model, inplace=True):
         model_disc.bcs = self.bcs
 
         self.external_variables = model.external_variables
+        # find where external variables begin in state vector
+        start_vals = []
+        for var in self.external_variables:
+            if isinstance(var, pybamm.Concatenation):
+                for child in var.children:
+                    start_vals += [self.y_slices[child.id][0].start]
+            elif isinstance(var, pybamm.Variable):
+                start_vals += [self.y_slices[var.id][0].start]
+
+        self.external_start = min(start_vals)
 
-        # Process initial condtions
         pybamm.logger.info("Discretise initial conditions for {}".format(model.name))
         ics, concat_ics = self.process_initial_conditions(model)
         model_disc.initial_conditions = ics
@@ -223,6 +232,7 @@ def set_variable_slices(self, variables):
                 start = end
 
         self.y_slices = y_slices
+        self.y_length = end
 
         # reset discretised_symbols
         self._discretised_symbols = {}

pybamm/simulation.py

@@ -115,6 +115,27 @@ def solve(self, t_eval=None, solver=None):
 
         self._solution = solver.solve(self.built_model, t_eval)
 
+    def step(self, dt, solver=None, external_variables=None):
+        """
+        A method to step the model forward one timestep. This method will
+        automatically build and set the model parameters if not already done so.
+
+        Parameters
+        ----------
+        dt : numeric type
+            The timestep over which to step the solution
+        solver : :class:`pybamm.BaseSolver`
+            The solver to use to solve the model.
+        external_variables : dict
+            A dictionary of external variables and their corresponding
+            values at the current time
+        """
+
+        if solver is None:
+            solver = self.solver
+
+        self._solution = solver.step(self.built_model, dt, external_variables)
+
     def plot(self, quick_plot_vars=None):
         """
         A method to quickly plot the outputs of the simulation.

pybamm/solvers/base_solver.py

@@ -97,7 +97,7 @@ def solve(self, model, t_eval):
         )
         return solution
 
-    def step(self, model, dt, npts=2, log=True):
+    def step(self, model, dt, npts=2, log=True, external_variables=None):
         """
         Step the solution of the model forward by a given time increment. The
         first time this method is called it executes the necessary setup by
@@ -113,6 +113,9 @@ def step(self, model, dt, npts=2, log=True):
         npts : int, optional
             The number of points at which the solution will be returned during
             the step dt. default is 2 (returns the solution at t0 and t0 + dt).
+        external_variables : dict
+            A dictionary of external variables and their corresponding
+            values at the current time
 
         Raises
         ------
@@ -147,6 +150,21 @@ def step(self, model, dt, npts=2, log=True):
         else:
             set_up_time = None
 
+        # load external variables into a state vector
+        self.y_ext = np.zeros((model.y_length, 1))
+        for var_name, var_vals in external_variables.items():
+            var = model.variables[var_name]
+            if isinstance(var, pybamm.Concatenation):
+                start = model.y_slices[var.children[0].id][0].start
+                stop = model.y_slices[var.children[-1].id][-1].stop
+                y_slice = slice(start, stop)
+
+            elif isinstance(var, pybamm.Variable):
+                start = model.y_slices[var.id][0].start
+                stop = model.y_slices[var.id][-1].stop
+                y_slice = slice(start, stop)
+            self.y_ext[y_slice] = var_vals
+
         # Step
         t_eval = np.linspace(self.t, self.t + dt, npts)
         solution, solve_time, termination = self.compute_solution(model, t_eval)

pybamm/spatial_methods/finite_volume.py

@@ -100,15 +100,6 @@ def preprocess_external_variables(self, var):
             A dictionary containing the new boundary conditions
         """
 
-        if isinstance(var, pybamm.Concatenation):
-            left_var = var.children[0]
-            right_var = var.children[-1]
-        else:
-            left_var = var
-            right_var = var
-
-        print("hello")
-
         new_bcs = {
             var: {
                 "left": (pybamm.BoundaryGradient(var, "left"), "Neumann"),

pybamm/spatial_methods/spatial_method.py

@@ -278,6 +278,9 @@ def internal_neumann_condition(
 
         raise NotImplementedError
 
+    def preprocess_external_variables(self, var):
+        return {}
+
     def boundary_value_or_flux(self, symbol, discretised_child):
         """
         Returns the boundary value or flux using the approriate expression for the

tests/integration/test_models/test_full_battery_models/test_lithium_ion/test_use_external_submodel.py

@@ -3,18 +3,43 @@
 #
 import pybamm
 import unittest
+import numpy as np
 
 
 # only works for statevector inputs
 class TestExternalSubmodel(unittest.TestCase):
     def test_external_temperature(self):
 
-        model_options = {"thermal": "x-full", "external submodels": ["thermal"]}
+        model_options = {
+            "thermal": "x-full",
+            "external submodels": ["thermal"],
+        }
+
         model = pybamm.lithium_ion.SPMe(model_options)
 
-        sim = pybamm.Simulation(model)
+        neg_pts = 5
+        sep_pts = 3
+        pos_pts = 5
+        tot_pts = neg_pts + sep_pts + pos_pts
+
+        var_pts = {
+            pybamm.standard_spatial_vars.x_n: neg_pts,
+            pybamm.standard_spatial_vars.x_s: sep_pts,
+            pybamm.standard_spatial_vars.x_p: pos_pts,
+            pybamm.standard_spatial_vars.r_n: 5,
+            pybamm.standard_spatial_vars.r_p: 5,
+        }
+
+        sim = pybamm.Simulation(model, var_pts=var_pts)
         sim.build()
 
+        t_eval = np.linspace(0, 0.17, 100)
+
+        for t in t_eval:
+            T = np.zeros((tot_pts, 1))
+            external_variables = {"Cell temperature": T}
+            sim.step(external_variables=external_variables)
+
 
 if __name__ == "__main__":
     print("Add -v for more debug output")