code: public static int cudnnCreatePersistentRNNPlan(
          cudnnRNNDescriptor rnnDesc, 
          int minibatch, 
          int dataType, 
          cudnnPersistentRNNPlan plan)
      {
          return checkResult(cudnnCreatePersistentRNNPlanNative(rnnDesc, minibatch, dataType, plan));
      }
docs: Expensive. Creates the plan for the specific settings.