refc[adjoint]: filter zero VJPs in setup_adj

tests/test_components/test_autograd.py

@@ -751,7 +751,7 @@ def objective(*args):
         sim_data = run(sim, task_name="adjoint_test", verbose=False)
         return 0 * postprocess(sim_data)
 
-    with AssertLogLevel("WARNING", contains_str="fields are zero"):
+    with AssertLogLevel("WARNING", contains_str="no sources"):
         grad = ag.grad(objective)(params0)
 
 

tidy3d/web/api/autograd/autograd.py

@@ -626,12 +626,6 @@ def _run_bwd(
     def vjp(data_fields_vjp: AutogradFieldMap) -> AutogradFieldMap:
         """dJ/d{sim.traced_fields()} as a function of Function of dJ/d{data.traced_fields()}"""
 
-        # filter out any data_fields_vjp with all 0's and skip the corresponding adjoint simulation
-        data_fields_vjp = {k: v for k, v in data_fields_vjp.items() if not np.allclose(v, 0)}
-        if not data_fields_vjp:
-            td.log.warning("All VJP fields are zero, skipping adjoint simulation")
-            return {k: 0 * v for k, v in sim_fields_original.items()}
-
         # build the (possibly multiple) adjoint simulations
         sims_adj = setup_adj(
             data_fields_vjp=data_fields_vjp,
@@ -858,8 +852,14 @@ def setup_adj(
 
     td.log.info("Running custom vjp (adjoint) pipeline.")
 
-    # immediately filter out any data_vjps with all 0's in the data
-    data_fields_vjp = {key: get_static(value) for key, value in data_fields_vjp.items()}
+    # filter out any data_fields_vjp with all 0's
+    data_fields_vjp = {
+        k: get_static(v) for k, v in data_fields_vjp.items() if not np.allclose(v, 0)
+    }
+
+    # if all entries are zero, there is no adjoint sim to run
+    if not data_fields_vjp:
+        return []
 
     # start with the full simulation data structure and either zero out the fields
     # that have no tracer data for them or insert the tracer data