Merge pull request #1107 from pybamm-team/issue-1104-mass-matrix-for-bdf

Issue 1104 mass matrix for bdf

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Features
 
+-   Added support for index 1 semi-explicit dae equations and sensitivity calculations to JAX BDF solver ([#1107](https://github.com/pybamm-team/PyBaMM/pull/1107))
 -   Allowed keyword arguments to be passed to `Simulation.plot()` ([#1099](https://github.com/pybamm-team/PyBaMM/pull/1099))
 
 ## Optimizations

pybamm/solvers/base_solver.py

@@ -451,9 +451,12 @@ def calculate_consistent_state(self, model, time=0, inputs=None):
         -------
         y0_consistent : array-like, same shape as y0_guess
             Initial conditions that are consistent with the algebraic equations (roots
-            of the algebraic equations)
+            of the algebraic equations). If self.root_method == None then returns
+            model.y0.
         """
         pybamm.logger.info("Start calculating consistent states")
+        if self.root_method is None:
+            return model.y0
         try:
             root_sol = self.root_method._integrate(model, [time], inputs)
         except pybamm.SolverError as e: