make copy of data

lint

Author: leo-collins

firedrake/function.py

@@ -812,7 +812,7 @@ def evaluate(self, function: Function) -> np.ndarray | Tuple[np.ndarray, ...]:
         f_at_points = assemble(interpolate(function, P0DG))
         f_at_points_io = Function(P0DG_io).assign(np.nan)
         f_at_points_io.interpolate(f_at_points)
-        result = f_at_points_io.dat.data_ro
+        result = f_at_points_io.dat.data_ro.copy()
 
         # If redundant, all points are now on rank 0, so we broadcast the result
         if self.redundant and self.mesh.comm.size > 1:

tests/firedrake/regression/test_point_eval_api.py

@@ -194,6 +194,10 @@ def test_point_evaluator_scalar(mesh_and_points):
     f_at_points_missing = eval_missing.evaluate(f)
     assert np.isnan(f_at_points_missing[-1])
 
+    # Can modify result
+    f_at_points *= 2.0
+    assert np.allclose(f_at_points, [0.4, 0.8, 1.2])
+
 
 @pytest.mark.parallel([1, 3])
 def test_point_evaluator_vector_tensor_mixed(mesh_and_points):