test: Enhance tests for interaction between deviceid and visible devices, and improve errors for invalid combinations

Author: EdCaunt

devito/operator/operator.py

@@ -1402,7 +1402,14 @@ def _physical_deviceid(self):
             if visible_devices is None:
                 return logical_deviceid
             else:
-                return visible_devices[logical_deviceid]
+                try:
+                    return visible_devices[logical_deviceid]
+                except IndexError:
+                    errmsg = (f"A deviceid value of {logical_deviceid} is not valid "
+                              f"with VISIBLE_DEVICES={visible_devices}. Note that "
+                              "deviceid corresponds to the logical index within the "
+                              "visible devices, not the physical device index.")
+                    raise ValueError(errmsg)
         else:
             return None
 

tests/test_gpu_common.py

@@ -149,6 +149,12 @@ def test_visible_devices_with_devito_deviceid(self):
             # So should be the second of the two visible devices specified (3)
             assert argmap._physical_deviceid == 3
 
+        with switchenv({'CUDA_VISIBLE_DEVICES': "1"}), switchconfig(deviceid=0):
+            op1 = Operator(eq)
+
+            argmap1 = op1.arguments()
+            assert argmap1._physical_deviceid == 1
+
     @pytest.mark.parallel(mode=2)
     def test_deviceid_per_rank(self, mode):
         """