More autograd improvements

CHANGELOG.md

@@ -35,6 +35,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Error when plotting mode plane PML and the simulation has symmetry.
 - Validators using `TriangleMesh.intersections_plane` will fall back on bounding box in case the method fails for a non-watertight mesh.
 - Bug when running the same `ModeSolver` first locally then remotely, or vice versa, in which case the cached data from the first run is always returned.
+- Gradient monitors for `PolySlab` only store fields at the center location along axis, reducing data usage.
+- Validate the forward simulation on the client side even when using `local_gradient=False` for server-side gradient processing.
 
 ## [2.7.1] - 2024-07-10
 

tidy3d/components/data/sim_data.py

@@ -1074,6 +1074,14 @@ def make_adjoint_sources(self, data_vjp_paths: set[tuple]) -> dict[str, SourceTy
             )
             sources_adj_all[mnt_data.monitor.name] = sources_adj
 
+        if not sources_adj_all:
+            raise ValueError(
+                "No adjoint sources created for this simulation. "
+                "This could indicate a bug in your setup, for example the objective function "
+                "output depending on a monitor that is not supported. If you encounter this error, "
+                "please examine your set up or contact customer support if you need more help."
+            )
+
         return sources_adj_all
 
     @property

tidy3d/components/structure.py

@@ -15,6 +15,7 @@
 from .autograd.types import AutogradFieldMap
 from .autograd.utils import get_static
 from .base import Tidy3dBaseModel, skip_if_fields_missing
+from .geometry.polyslab import PolySlab
 from .geometry.utils import GeometryType, validate_no_transformed_polyslabs
 from .grid.grid import Coords
 from .medium import AbstractCustomMedium, Medium2D, MediumType
@@ -203,8 +204,13 @@ def make_adjoint_monitors(
         box = self.geometry.bounding_box
 
         # we dont want these fields getting traced by autograd, otherwise it messes stuff up
-        size = tuple(get_static(x) for x in box.size)  # TODO: expand slightly?
-        center = tuple(get_static(x) for x in box.center)
+
+        size = [get_static(x) for x in box.size]  # TODO: expand slightly?
+        center = [get_static(x) for x in box.center]
+
+        # polyslab only needs fields at the midpoint along axis
+        if isinstance(self.geometry, PolySlab):
+            size[self.geometry.axis] = 0
 
         mnt_fld = FieldMonitor(
             size=size,

tidy3d/web/api/autograd/autograd.py

@@ -388,12 +388,14 @@ def _run_primitive(
 
     td.log.info("running primitive '_run_primitive()'")
 
+    # compute the combined simulation for both local and remote, so we can validate it
+    sim_combined = setup_fwd(
+        sim_fields=sim_fields,
+        sim_original=sim_original,
+        local_gradient=local_gradient,
+    )
+
     if local_gradient:
-        sim_combined = setup_fwd(
-            sim_fields=sim_fields,
-            sim_original=sim_original,
-            local_gradient=local_gradient,
-        )
         sim_data_combined, _ = _run_tidy3d(sim_combined, task_name=task_name, **run_kwargs)
 
         field_map = postprocess_fwd(