polishing automatic simulation reduction for mode solver

Author: dbochkov-flexcompute

tidy3d/plugins/mode/mode_solver.py

@@ -973,7 +973,7 @@ def reduced_simulation_copy(self):
         This might significantly reduce upload time in the presence of custom mediums.
         """
 
-        # we preserve extracells along the normal direction to ensure there is enough data for
+        # we preserve extra cells along the normal direction to ensure there is enough data for
         # subpixel
         extended_grid = self._get_solver_grid(preserve_layer_behind=True, truncate_symmetry=False)
         grids_1d = extended_grid.boundaries

tidy3d/web/api/mode.py

@@ -86,9 +86,8 @@ def run(
         console = get_logging_console()
 
     if reduce_simulation == "auto":
-        sim = mode_solver.simulation
-        contains_custom = any(isinstance(s.medium, AbstractCustomMedium) for s in sim.structures)
-        contains_custom = contains_custom or isinstance(sim.medium, AbstractCustomMedium)
+        sim_mediums = mode_solver.simulation.scene.mediums
+        contains_custom = any(isinstance(med, AbstractCustomMedium) for med in sim_mediums)
         reduce_simulation = contains_custom
 
         if reduce_simulation: