r != 1is not yet supported. There is one exception, reverse_one is allowed because there is only one zero order forward direction. After such an operation, only the zero order forward results are retained (the higher order forward results are lost).
|reverse_one||First Order Reverse Mode|
|reverse_two||Second Order Reverse Mode|
|reverse_any||Any Order Reverse Mode|
|subgraph_reverse||Reverse Mode Using Subgraphs|