We introduce SubFlow-a dynamic adaptation and execution strategy for a deep neural network (DNN), which enables real-time DNN inference and training. The goal of SubFlow is to complete the execution of a DNN task within a timing constraint that may dynamically change while ensuring comparable performance to executing the full network by executing a subset of the DNN at run-time. To this end, we propose two online algorithms that enable SubFlow: 1) dynamic construction of a sub-network which constructs the best sub-network of the DNN in terms of size and configuration, and 2) time-bound execution which executes the sub-network within a given time budget either for inference or training. We implement and open-source SubFlow by extending TensorFlow with full compatibility by adding SubFlow operations for convolutional and fully-connected layers of a DNN. We evaluate SubFlow with three popular DNN models (LeNet-5, AlexNet, and KWS), which shows that it provides flexible run-time execution and increases the utility of a DNN under dynamic timing constraints, e.g., 1x-6.7x range of dynamic execution speed with average -3% of performance (inference accuracy) difference. We also implement an autonomous robot as an example system that uses SubFlow and demonstrate that its obstacle detection DNN is flexibly executed to meet a range of deadlines that varies depending on its running speed.
