api: fix sparse positon match with -1

Author: mloubout

devito/types/sparse.py

@@ -112,7 +112,8 @@ def __shape_setup__(cls, **kwargs):
             loc_shape = []
             assert len(dimensions) == len(shape)
             for i, (d, s) in enumerate(zip(dimensions, shape)):
-                if i == cls._sparse_position:
+                if i == cls._sparse_position or \
+                   (cls._sparse_position == -1 and i == len(dimensions)-1):
                     loc_shape.append(glb_npoint[grid.distributor.myrank])
                 elif d in grid.dimensions:
                     loc_shape.append(grid.size_map[d].loc)