Detach solver statistics save from data save, and always save

src/porepy/models/protocol.py

@@ -1020,10 +1020,11 @@ def save_data_time_step(self) -> None:
                 * `list`: Export if time is in the list. If the list is empty, then no
                 times are exported.
 
-            In addition, save the solver statistics to file if the option is set.
-
             """
 
+        def save_statistics(self) -> None:
+            """Save the solver statistics to file if the option is set."""
+
         def initialize_data_saving(self) -> None:
             """Initialize data saving.
 

src/porepy/models/solution_strategy.py

@@ -485,18 +485,22 @@ def after_time_step_convergence(self) -> None:
 
         1. Call :meth:`update_time_step_solution`.
         2. Call :meth:`save_data_time_step`.
+        3. Call :meth:`save_statistics`.
 
         """
         self.update_time_step_solution()
         self.save_data_time_step()
+        self.save_statistics()
 
     def after_time_step_failure(self) -> None:
         """Called after a time step has failed to converge.
 
         The base method reverts the trial time step being executed.
+        It also calls :meth:`save_statistics`.
 
         """
         self.revert_trial_time_step_solution()
+        self.save_statistics()
 
     def reset_state_from_file(self) -> None:
         """Reset states but through a restart from file.
@@ -777,7 +781,7 @@ def revert_trial_time_step_solution(self) -> None:
 
     def after_simulation(self) -> None:
         """Run at the end of simulation. Can be used for cleanup etc."""
-        pass
+        self.save_statistics()
 
     def assemble_linear_system(self) -> solvers.LinearSystem:
         """Assemble and return the linearized system.

src/porepy/numerics/solvers/nonlinear_solvers.py

@@ -536,8 +536,7 @@ def check_convergence(
         """Check convergence and divergence based on passed criteria.
 
         Parameters:
-            model: The model instance specifying the problem to be solved, knowing
-                of its metrics for measuring states and residuals.
+            model: The model instance specifying the problem to be solved.
             nonlinear_increment: Newly obtained solution increment vector.
 
         Returns:

src/porepy/viz/data_saving_model_mixin.py

@@ -58,9 +58,6 @@ def save_data_time_step(self) -> None:
         if do_export:
             self.write_pvd_and_vtu()
 
-        # Save solver statistics to file.
-        self.nonlinear_solver_statistics.save()
-
         # Collecting and storing data in runtime for analysis. If default value of None
         # is returned, nothing is stored to not burden memory.
         if not self._is_time_dependent():
@@ -75,6 +72,10 @@ def save_data_time_step(self) -> None:
                 if collected_data is not None:
                     self.results.append(collected_data)
 
+    def save_statistics(self):
+        """Save solver statistics to file."""
+        self.nonlinear_solver_statistics.save()
+
     def collect_data(self) -> Any:
         """Collect relevant simulation data to be stored in attr:`results`.
 

tests/viz/test_solver_statistics.py

@@ -624,6 +624,9 @@ def test_solver_statistics_save_in_model(path, exists):
     model = DummyModel(params)
     model.prepare_simulation()
 
+    # Save the solver statistics explicitly.
+    model.save_statistics()
+
     # Check whether file was saved and has correct suffix.
     if exists:
         assert model.nonlinear_solver_statistics.path.exists()