Make IDAKLU output variables compatible with Experiments #4386
Description
This was initially reported as a bug (see report below) but it turns out it is not an implemented feature yet. It seems the main issue is that when a new experiment step is initialised with the previous step solution, that one is empty so the relevant variables are not available. I believe that amending the last_state so it stores the whole state vector even when output variables are used should fix this.
PyBaMM Version
develop
Python Version
3.11.6
Describe the bug
I am running a model with the IDAKLUSolver and some output_variables. These include, amongst others, the "Discharge capacity [A.h]", however PyBaMM complains that that variable is not found.
Steps to Reproduce
import pybamm
pybamm.set_logging_level("NOTICE")
model = pybamm.lithium_ion.DFN()
output_variables = ["Discharge capacity [A.h]", "Time [s]", "Current [A]", "Voltage [V]"]
solver = pybamm.IDAKLUSolver(output_variables=output_variables)
experiment = pybamm.Experiment(
[
(
"Charge at 1C until 4.2 V",
"Hold at 4.2 V until C/50",
"Rest for 1 hour",
)
]
)
sim = pybamm.Simulation(
model,
experiment=experiment,
solver=solver,
)
sol = sim.solve()Relevant log output
Traceback (most recent call last):
File "/home/brosaplanella/PyBaMM/src/pybamm/models/base_model.py", line 808, in set_initial_conditions_from
final_state = solution[var.name]
~~~~~~~~^^^^^^^^^^
File "/home/brosaplanella/PyBaMM/src/pybamm/solvers/solution.py", line 547, in __getitem__
self.update(key)
File "/home/brosaplanella/PyBaMM/src/pybamm/solvers/solution.py", line 481, in update
raise KeyError(
KeyError: "Cannot process variable 'Discharge capacity [A.h]' as it was not part of the solve. Please re-run the solve with `output_variables` set to include this variable."
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/home/brosaplanella/battery_modelling/degradation-data/examples/mwe.py", line 29, in <module>
sol = sim.solve()
^^^^^^^^^^^
File "/home/brosaplanella/PyBaMM/src/pybamm/simulation.py", line 702, in solve
step_solution = solver.step(
^^^^^^^^^^^^
File "/home/brosaplanella/PyBaMM/src/pybamm/solvers/base_solver.py", line 1222, in step
_, concatenated_initial_conditions = model.set_initial_conditions_from(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/brosaplanella/PyBaMM/src/pybamm/models/base_model.py", line 810, in set_initial_conditions_from
raise pybamm.ModelError(
pybamm.expression_tree.exceptions.ModelError: To update a model from a solution, each variable in model.initial_conditions must appear in the solution with the same key as the variable name. In the solution provided, 'Cannot process variable 'Discharge capacity [A.h]' as it was not part of the solve. Please re-run the solve with `output_variables` set to include this variable.' was not found.