pystencils: easy access to center

field.py

@@ -204,6 +204,10 @@ class Field(object):
         offsetList[coordId] = offset
         return Field.Access(self, tuple(offsetList))
 
+    def center(self):
+        center = tuple([0] * self.spatialDimensions)
+        return Field.Access(self, center)
+
     def __getitem__(self, offset):
         if type(offset) is np.ndarray:
             offset = tuple(offset)

transformations.py

@@ -540,7 +540,8 @@ def getOptimalLoopOrdering(fields):
 
     layouts = set([field.layout for field in fields])
     if len(layouts) > 1:
-        raise ValueError("Due to different layout of the fields no optimal loop ordering exists " + str(layouts))
+        raise ValueError("Due to different layout of the fields no optimal loop ordering exists " +
+                         str({f.name: f.layout for f in fields}))
     layout = list(layouts)[0]
     return list(layout)