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CPU cache misses and branch mispredictions waste CPU cycles and affect program performance. Such software inefficiencies could be neither eliminated by existing compilers nor avoided by developers. In this paper, we propose a novel approach, named PERDICE, to automatically discover such performance bugs by leveraging concolic execution. PERDICE adopts a new path exploration algorithm to discover such software inefficiencies. In particular, we measure performance losses in the granularity of program locations (e.g., instructions, source code lines) instead of paths to avoid getting stuck into the code without software inefficiencies. Moreover, when scoring test inputs, our new approach prefers the test inputs incurring increments in performance losses. This strategy allows PERDICE to avoid getting stuck into the software inefficiencies that have been found. We have implemented PERDICE for both PC (X86 instructions) and Android smartphones (ARM instructions). The experimental results with real-world desktop software and Android native code show that PERDICE outperforms the other four popular algorithms and PROFs (a multi-path performance profiler) in terms of the speed to discover software inefficiencies and the severity (i.e, amount of wasted CPU cycles) of inefficiencies.

Dynamic symbolic execution is an important automated testing technique. Firstly, we introduce the traditional symbolic execution and dynamic symbolic execution technology, and then review the research status of Python application testing with dynamic symbolic execution technology. Then we compare and analyze the dynamic symbolic execution tools with the existing Python programs and Architectures, performance, and supported data types. Finally, the development direction of this field prospects. It is helpful for researchers to understand the progress of dynamic symbolic execution technology in current Python program and lay a foundation for future research work.

Study on diffusion behaviors, such as contagion of virus, adoption of production, and information propagation, is one of the hottest topics of social network research. The conventional models usually focus on a particular factor that influences the contagion process. A novel model of diffusion based on multiple behavior evidence fusion is proposed on the analysis of prevalent social network data set, which can simulate the information propagation process with the fitting goodness of 0.79. In this model, impact factors, i.e. the influence between neighborhood, and the activity of user, are taken into account together and fused into combined evidence mass function, which can be used to infer users' forwarding behavior by D-S theory reasoning. Series of experiments tested on the published Enron email data set show that the multiple evidence fusion based diffusion model (MEFDM) is reasonable and feasible in demonstrating the cascading of information in the social network.