Formal program specifications are essential for various software engineering tasks, such as program verification, program synthesis, code debugging and software testing. However, manually inferring formal program specifications is not only time-consuming but also error-prone. In addition, it requires substantial expertise. Natural language comments contain rich semantics about behaviors of code, making it feasible to infer program specifications from comments. Inspired by this, we develop a tool, named C2S, to automate the specification synthesis task by translating natural language comments into formal program specifications. Our approach firstly constructs alignments between natural language word and specification tokens from existing comments and their corresponding specifications. Then for a given method comment, our approach assembles tokens that are associated with words in the comment from the alignments into specifications guided by specification syntax and the context of the target method. Our tool successfully synthesizes 1,145 specifications for 511 methods of 64 classes in 5 different projects, substantially outperforming the state-of-the-art. The generated specifications are also used to improve a number of software engineering tasks like static taint analysis, which demonstrates the high quality of the specifications.

Most neural network applications rely on the fundamental approximation property of feedforward networks. Supervised learning is a means of implementing this approximate mapping. In a realistic problem setting, a mechanism is needed to devise this learning process based on available data, which encompasses choosing an appropriate set of parameters in order to avoid overfitting, using an efficient learning algorithm measured by computation and memory complexities, ensuring the accuracy of the training procedures as measured by the training error, and testing and cross-validation for generalization. We develop a comprehensive supervised learning algorithm to address these issues. The algorithm combines training and pruning into one procedure by utilizing a common observation of Jacobian rank deficiency in feedforward networks. The algorithm not only reduces the training time and overall complexity but also achieves training accuracy and generalization capabilities comparable to more standard approaches. Extensive simulation results are provided to demonstrate the effectiveness of the algorithm.

In this paper we introduce an advanced supervised training method for neural networks. It is based on Jacobian rank deficiency and it is formulated, in some sense, in the spirit of the Gauss-Newton algorithm. The Levenberg-Marquardt algorithm, as a modified Gauss-Newton, has been used successfully in solving nonlinear least squares problems including neural-network training. It outperforms (in terms of training accuracy, convergence properties, overall training time, etc.) the basic backpropagation and its variations with variable learning rate significantly, however, with higher computation and memory complexities within each iteration. The new method developed in this paper is aiming at improving convergence properties, while reducing the memory and computation complexities in supervised training of neural networks. Extensive simulation results are provided to demonstrate the superior performance of the new algorithm over the Levenberg-Marquardt algorithm.