Improved Highway Network Block for Training Very Deep Neural Networks

Very deep networks are successful in various tasks with reported results surpassing human performance. However, training such very deep networks is not trivial. Typically, the problems of learning the identity function and feature reuse can work together to plague optimization of very deep networks. In this paper, we propose a highway network with gate constraints that addresses the aforementioned problems, and thus alleviates the difficulty of training. Namely, we propose two variants of highway network,
HWGC
and
HWCC
, employing feature summation and concatenation respectively. The proposed highway networks, besides being more computationally efficient, are shown to have more interesting learning characteristics such as natural learning of hierarchical and robust representations due to a more effective usage of model depth, fewer gates for successful learning, better generalization capacity and faster convergence than the original highway network. Experimental results show that our models outperform the original highway network and many state-of-the-art models. Importantly, we observe that our second model with feature concatenation and compression consistently outperforms our model with feature summation of similar depth, the original highway network, many state-of-the-art models and even ResNets on four benchmarking datasets which are CIFAR-10, CIFAR-100, Fashion-MNIST, SVHN and imagenet-2012 (ILSVRC) datasets. Furthermore, the second proposed model is more computationally efficient than the state-of-the-art in view of training, inference time and GPU memory resource, which strongly supports real-time applications. Using a similar number of model parameters for the CIFAR-10, CIFAR-100, Fashion-MNIST and SVHN datasets, the significantly shallower proposed model can surpass the performance of ResNet-110 and ResNet-164 that are roughly 6 and 8 times deeper, respectively. Similarly, for the imagenet dataset, the proposed models surpass the performance of ResNet-101 and ResNet-152 that are roughly three times deeper.