“cf963d96b6c468cea859bcff653872cad445a5bc”上不存在“mobile/src/operators/kernel/arm/proposal_kernel.cpp”
For input argument with a list of variables, drop_empty_grad is not allowed because it makes the correspondence bewteen a variable and its gradient ambiguous. Use REGISTER_OP_EX to register the op or call InputGrad(?,false) in GradOpDescMaker.