for PML or absorbers along a zero dim, raise error instead of warning

- update changelog

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Update versions of `boto3`, `requests`, and `click`.
 - python 3.7 no longer tested nor supported.
 - Remove warning that monitors now have `colocate=True` by default.
+- If `PML` or any absorbing boundary condition is used along a direction where the `Simulation` size is zero, an error will be raised, rather than just a warning.
 
 ### Fixed
 - If no adjoint sources for one simulation in an objective function, make a mock source with zero amplitude and warn user.

tests/test_components/test_simulation.py

@@ -461,7 +461,7 @@ def test_validate_plane_wave_boundaries(log_capture):
 
 def test_validate_zero_dim_boundaries(log_capture):
 
-    # zero-dim simulation with an absorbing boundary in that direction should warn
+    # zero-dim simulation with an absorbing boundary in that direction should error
     src = td.PlaneWave(
         source_time=td.GaussianPulse(freq0=2.5e14, fwidth=1e13),
         center=(0, 0, 0),
@@ -470,27 +470,27 @@ def test_validate_zero_dim_boundaries(log_capture):
         pol_angle=0.0,
     )
 
-    td.Simulation(
-        size=(1, 1, 0),
-        run_time=1e-12,
-        sources=[src],
-        boundary_spec=td.BoundarySpec(
-            x=td.Boundary.periodic(),
-            y=td.Boundary.periodic(),
-            z=td.Boundary.pml(),
-        ),
-    )
-    assert_log_level(log_capture, "WARNING")
+    with pytest.raises(pydantic.ValidationError):
+        td.Simulation(
+            size=(1, 1, 0),
+            run_time=1e-12,
+            sources=[src],
+            boundary_spec=td.BoundarySpec(
+                x=td.Boundary.periodic(),
+                y=td.Boundary.periodic(),
+                z=td.Boundary.pml(),
+            ),
+        )
 
-    # zero-dim simulation with an absorbing boundary any other direction should not warn
+    # zero-dim simulation with an absorbing boundary any other direction should not error
     td.Simulation(
         size=(1, 1, 0),
         run_time=1e-12,
         sources=[src],
         boundary_spec=td.BoundarySpec(
             x=td.Boundary.pml(),
             y=td.Boundary.stable_pml(),
-            z=td.Boundary.pec(),
+            z=td.Boundary.periodic(),
         ),
     )
 
@@ -611,6 +611,7 @@ def test_plot_1d_sim():
         size=(0, 0, 1),
         grid_spec=grid_spec,
         run_time=1e-13,
+        boundary_spec=td.BoundarySpec.all_sides(boundary=td.Periodic()),
     )
     _ = s.plot(y=0)
     plt.close()

tests/test_plugins/test_adjoint.py

@@ -849,6 +849,11 @@ def test_structure_overlaps():
         grid_spec=td.GridSpec(wavelength=1.0),
         run_time=1e-12,
         sources=(src,),
+        boundary_spec=td.BoundarySpec(
+            x=td.Boundary.pml(),
+            y=td.Boundary.periodic(),
+            z=td.Boundary.pml(),
+        ),
     )
 
 

tidy3d/components/simulation.py

@@ -383,17 +383,16 @@ def tfsf_with_symmetry(cls, val, values):
 
     @pydantic.validator("boundary_spec", always=True)
     def boundaries_for_zero_dims(cls, val, values):
-        """Warn if an absorbing boundary is used along a zero dimension."""
+        """Error if an absorbing boundary is used along a zero dimension."""
         boundaries = val.to_list
         size = values.get("size")
         for dim, (boundary, size_dim) in enumerate(zip(boundaries, size)):
             num_absorbing_bdries = sum(isinstance(bnd, AbsorberSpec) for bnd in boundary)
             if num_absorbing_bdries > 0 and size_dim == 0:
-                log.warning(
-                    f"If the simulation is intended to be 2D in the plane normal to the "
-                    f"{'xyz'[dim]} axis, using a PML or absorbing boundary along that axis "
-                    f"is incorrect. Consider using a 'Periodic' boundary along {'xyz'[dim]}.",
-                    custom_loc=["boundary_spec", "xyz"[dim]],
+                raise SetupError(
+                    f"The simulation has zero size along the {'xyz'[dim]} axis, so "
+                    "using a PML or absorbing boundary along that axis is incorrect. "
+                    f"Use either 'Periodic' or 'BlochBoundary' along {'xyz'[dim]}."
                 )
         return val