[lang] free ndarray memory on the base class

classes inheriting from Ndarray should have their memory released

Author: Bernardo Covas

python/taichi/lang/_ndarray.py

@@ -60,6 +60,16 @@ def __getitem__(self, key):
         """
         raise NotImplementedError()
 
+    def __del__(self):
+        rt = impl.get_runtime()
+        if (
+            self.arr is not None and
+            impl is not None and
+            rt is not None and
+            rt.prog is not None
+        ):
+            impl.get_runtime().prog.delete_ndarray(self.arr)
+
     @python_scope
     def fill(self, val):
         """Fills ndarray with a specific scalar value.
@@ -243,9 +253,6 @@ def __init__(self, dtype, arr_shape):
         self.shape = tuple(self.arr.shape)
         self.element_type = dtype
 
-    def __del__(self):
-        if impl is not None and impl.get_runtime() is not None and impl.get_runtime().prog is not None:
-            impl.get_runtime().prog.delete_ndarray(self.arr)
 
     @property
     def element_shape(self):