Warning about symmetry expansion in ModeSolver and ModeSimulation

removing 'symmetry' argument from 'subsection'

Author: momchil-flex

CHANGELOG.md

@@ -27,6 +27,9 @@ or `Absorber` classes (or when invoking `pml()`, `stable_pml()`, or `absorber()`
 with fewer layers than recommended.
 - Warnings and error messages originating from `Structure`, `Source`, or `Monitor` classes now refer to problematic objects by their user-supplied `name` attribute, alongside their index.
 - File downloads are atomic. Interruptions or failures during download will no longer result in incomplete files.
+- Warnings are now generated (instead of errors) when instantiating `PML`, `StablePML`, or `Absorber` classes (or when invoking `pml()`, `stable_pml()`, or `absorber()` functions) with fewer layers than recommended.
+- `Simulation.subsection` can no longer take `symmetry` as an argument - the symmetry is always taken from the original simulation.
+- If a mode simulation is crossing a symmetry plane of the larger simulation domain, but the mode plane is not symmetric, a warning is issued that it will be expanded symmetrically. Previously this warning only happened during the solver run.
 
 ### Fixed
 - Arrow lengths are now scaled consistently in the X and Y directions, and their lengths no longer exceed the height of the plot window.

tests/test_components/test_mode.py

@@ -328,3 +328,54 @@ def get_mode_sim_data():
 def test_mode_sim_data():
     sim_data = get_mode_sim_data()
     _ = sim_data.plot_field("Ey", ax=AX, mode_index=0, f=FS[0])
+
+
+def test_plane_crosses_symmetry_plane_warning(monkeypatch):
+    """Test that a warning is issued if the mode plane crosses a symmetry plane but the centers do not match."""
+
+    # Simulation with symmetry in x (axis 0), center at (0, 0, 0)
+    sim_center = (0, 0, 0)
+    sim_size = (10, 5, 5)
+    sim_symmetry = (1, 0, 0)  # symmetry in x
+
+    # Plane crosses x=0 (symmetry plane), but plane center != sim center
+    plane_center = (2, 0, 0)
+    plane_size = (5, 0, 5)
+    plane = td.Box(center=plane_center, size=plane_size)
+
+    # Should warn
+    with AssertLogLevel("WARNING"):
+        _ = td.ModeSimulation(
+            center=sim_center,
+            size=sim_size,
+            symmetry=sim_symmetry,
+            plane=plane,
+            mode_spec=td.ModeSpec(),
+            freqs=[td.C_0],
+        )
+
+    # Now, plane center matches sim center: should NOT warn
+    plane_center2 = (0, 0, 0)
+    plane2 = td.Box(center=plane_center2, size=plane_size)
+    with AssertLogLevel("INFO"):
+        _ = td.ModeSimulation(
+            center=sim_center,
+            size=sim_size,
+            symmetry=sim_symmetry,
+            plane=plane2,
+            mode_spec=td.ModeSpec(),
+            freqs=[td.C_0],
+        )
+
+    # Plane does NOT cross symmetry plane: should NOT warn
+    plane_center3 = (5, 0, 0)
+    plane3 = td.Box(center=plane_center3, size=plane_size)
+    with AssertLogLevel("INFO"):
+        _ = td.ModeSimulation(
+            center=sim_center,
+            size=sim_size,
+            symmetry=sim_symmetry,
+            plane=plane3,
+            mode_spec=td.ModeSpec(),
+            freqs=[td.C_0],
+        )

tidy3d/components/eme/simulation.py

@@ -1097,6 +1097,7 @@ def subsection(
         grid_spec: Union[GridSpec, Literal["identical"]] = None,
         eme_grid_spec: Union[EMEGridSpec, Literal["identical"]] = None,
         symmetry: Optional[tuple[Symmetry, Symmetry, Symmetry]] = None,
+        warn_symmetry_expansion: bool = True,
         monitors: Optional[tuple[MonitorType, ...]] = None,
         remove_outside_structures: bool = True,
         remove_outside_custom_mediums: bool = False,
@@ -1123,6 +1124,8 @@ def subsection(
             New simulation symmetry. If ``None``, then it is inherited from the original
             simulation. Note that in this case the size and placement of new simulation domain
             must be commensurate with the original symmetry.
+        warn_symmetry_expansion : bool = True
+            Whether to warn when the subsection is expanded to preserve symmetry.
         monitors : Tuple[MonitorType, ...] = None
             New list of monitors. If ``None``, then the monitors intersecting the new simulation
             domain are inherited from the original simulation.
@@ -1160,7 +1163,7 @@ def subsection(
         new_sim = super().subsection(
             region=new_region,
             grid_spec=grid_spec,
-            symmetry=symmetry,
+            warn_symmetry_expansion=warn_symmetry_expansion,
             monitors=monitors,
             remove_outside_structures=remove_outside_structures,
             remove_outside_custom_mediums=remove_outside_custom_mediums,

tidy3d/components/mode/mode_solver.py

@@ -211,6 +211,30 @@ def plane_in_sim_bounds(cls, val, values):
             raise SetupError("'ModeSolver.plane' must intersect 'ModeSolver.simulation'.")
         return val
 
+    @pydantic.validator("plane", always=True)
+    @skip_if_fields_missing(["simulation"])
+    def _warn_plane_crosses_symmetry(cls, val, values):
+        """Warn if the mode plane crosses the symmetry plane of the underlying simulation but
+        the centers do not match."""
+        simulation = values.get("simulation")
+        bounds = val.bounds
+        # now check in each dimension whether we cross symmetry plane
+        for dim in range(3):
+            if simulation.symmetry[dim] != 0:
+                crosses_symmetry = (
+                    bounds[0][dim] < simulation.center[dim]
+                    and bounds[1][dim] > simulation.center[dim]
+                )
+                if crosses_symmetry:
+                    if not isclose(val.center[dim], simulation.center[dim]):
+                        log.warning(
+                            f"The original simulation is symmetric along {'xyz'[dim]} direction. "
+                            "The mode simulation region does cross the symmetry plane but is "
+                            "not symmetric with respect to it. To preserve correct symmetry, "
+                            "the requested simulation region will be expanded by the solver."
+                        )
+        return val
+
     def _post_init_validators(self) -> None:
         self._validate_mode_plane_radius(
             mode_spec=self.mode_spec,
@@ -2539,6 +2563,7 @@ def reduced_simulation_copy(self):
             region=new_sim_box,
             monitors=[],
             sources=[],
+            warn_symmetry_expansion=False,  # we already warn upon mode solver creation
             grid_spec="identical",
             boundary_spec=new_bspec,
             remove_outside_custom_mediums=True,

tidy3d/components/simulation.py

@@ -1701,6 +1701,7 @@ def subsection(
         boundary_spec: BoundarySpec = None,
         grid_spec: Union[GridSpec, Literal["identical"]] = None,
         symmetry: Optional[tuple[Symmetry, Symmetry, Symmetry]] = None,
+        warn_symmetry_expansion: bool = True,
         sources: Optional[tuple[SourceType, ...]] = None,
         monitors: Optional[tuple[MonitorType, ...]] = None,
         remove_outside_structures: bool = True,
@@ -1728,6 +1729,8 @@ def subsection(
             New simulation symmetry. If ``None``, then it is inherited from the original
             simulation. Note that in this case the size and placement of new simulation domain
             must be commensurate with the original symmetry.
+        warn_symmetry_expansion : bool = True
+            Whether to warn when the subsection is expanded to preserve symmetry.
         sources : Tuple[SourceType, ...] = None
             New list of sources. If ``None``, then the sources intersecting the new simulation
             domain are inherited from the original simulation.
@@ -1805,12 +1808,13 @@ def subsection(
                         center = (new_bounds[0][dim] + new_bounds[1][dim]) / 2
 
                         if not math.isclose(center, self.center[dim]):
-                            log.warning(
-                                f"The original simulation is symmetric along {'xyz'[dim]} direction. "
-                                "The requested new simulation region does cross the symmetry plane but is "
-                                "not symmetric with respect to it. To preserve correct symmetry, "
-                                "the requested simulation region is expanded symmetrically."
-                            )
+                            if warn_symmetry_expansion:
+                                log.warning(
+                                    f"The original simulation is symmetric along {'xyz'[dim]} direction. "
+                                    "The requested new simulation region does cross the symmetry plane but is "
+                                    "not symmetric with respect to it. To preserve correct symmetry, "
+                                    "the requested simulation region is expanded symmetrically."
+                                )
                             new_bounds[0][dim] = 2 * self.center[dim] - new_bounds[1][dim]
 
         # symmetry and grid spec treatments could change new simulation bounds