u_sub_e(lhs_field, rhs_field, out)¶
Builtin message function that computes a message on an edge by performing element-wise sub between features of src and edge if the features have the same shape; otherwise, it first broadcasts the features to a new shape and performs the element-wise operation.
Broadcasting follows NumPy semantics. Please see https://docs.scipy.org/doc/numpy/user/basics.broadcasting.html for more details about the NumPy broadcasting semantics.
>>> import dgl >>> message_func = dgl.function.u_sub_e('h', 'h', 'm')