Faster Mutation Analysis via Equivalence Modulo States

Mutation analysis has many applications, such as asserting the quality of test suites and localizing faults. One important bottleneck of mutation analysis is scalability. The latest work explores the possibility of reducing the redundant execution via split-stream execution. However, split-stream execution is only able to remove redundant execution before the first mutated statement. In this paper we try to also reduce some of the redundant execution after the execution of the first mutated statement. We observe that, although many mutated statements are not equivalent, the execution result of those mutated statements may still be equivalent to the result of the original statement. In other words, the statements are equivalent modulo the current state. In this paper we propose a fast mutation analysis approach, AccMut. AccMut automatically detects the equivalence modulo states among a statement and its mutations, then groups the statements into equivalence classes modulo states, and uses only one process to represent each class. In this way, we can significantly reduce the number of split processes. Our experiments show that our approach can further accelerate mutation analysis on top of split-stream execution with a speedup of 2.56x on average.Comment: Submitted to conferenc

A measurement based rogue ap detection scheme

points (APs) that pretend to be legitimate APs to lure users to connect to them. We propose a practical timing based technique that allows the user to avoid connecting to rogue APs. Our method employs the round trip time between the user and the DNS server to independently determine whether an AP is legitimate or not without assistance from the WLAN operator. We implemented our detection technique on commercially available wireless cards to evaluate their performance. I

A parallel numerical algorithm by combining MPI and OpenMP programming models with applications in gravity field recovery

Satellite gravimetry missions have enabled the calculation of high-accuracy and high-resolution Earth gravity field models from satellite-to-satellite tracking data and gravitational gradients. However, calculating high maximum degree/order (e.g., 240 or even higher) gravity field models using the least squares method is time-consuming due to the vast amount of gravimetry observations. To improve calculation efficiency, a parallel algorithm has been developed by combining Message Passing Interface (MPI) and Open Multi-Processing (OpenMP) programming models to calculate and invert normal equations for the Earth gravity field recovery. The symmetrical feature of normal equations has been implemented to speed up the calculation progress and reduce computation time. For example, the computation time to generate the normal equation of an IGGT_R1 test version of degree/order 240 was reduced from 88 h to 27 h by considering the symmetrical feature. Here, the calculation was based on the high-performance computing cluster with 108 cores in the School of Geodesy and Geomatics, at Wuhan University. Additionally, the MPI parallel Gaussian-Jordan elimination method was modified to invert normal equation matrices and scaled up to 100 processor cores in this study while the traditional method was limited in a certain number of processors. Furthermore, the Cholesky decomposition from the ScaLAPACK library was used to compare with the parallel Gauss-Jordan elimination method. The numerical algorithm has effectively reduced the amount of calculation and sped up the calculation progress, and has been successfully implemented in applications such as building the gravity field models IGGT_R1 and IGGT_R1C.</p

The Lifecycle and Cascade of WeChat Social Messaging Groups

Social instant messaging services are emerging as a transformative form with which people connect, communicate with friends in their daily life - they catalyze the formation of social groups, and they bring people stronger sense of community and connection. However, research community still knows little about the formation and evolution of groups in the context of social messaging - their lifecycles, the change in their underlying structures over time, and the diffusion processes by which they develop new members. In this paper, we analyze the daily usage logs from WeChat group messaging platform - the largest standalone messaging communication service in China - with the goal of understanding the processes by which social messaging groups come together, grow new members, and evolve over time. Specifically, we discover a strong dichotomy among groups in terms of their lifecycle, and develop a separability model by taking into account a broad range of group-level features, showing that long-term and short-term groups are inherently distinct. We also found that the lifecycle of messaging groups is largely dependent on their social roles and functions in users' daily social experiences and specific purposes. Given the strong separability between the long-term and short-term groups, we further address the problem concerning the early prediction of successful communities. In addition to modeling the growth and evolution from group-level perspective, we investigate the individual-level attributes of group members and study the diffusion process by which groups gain new members. By considering members' historical engagement behavior as well as the local social network structure that they embedded in, we develop a membership cascade model and demonstrate the effectiveness by achieving AUC of 95.31% in predicting inviter, and an AUC of 98.66% in predicting invitee.Comment: 10 pages, 8 figures, to appear in proceedings of the 25th International World Wide Web Conference (WWW 2016

Tailoring excitonic states of van der Waals bilayers through stacking configuration, band alignment and valley-spin

Excitons in monolayer semiconductors have large optical transition dipole for strong coupling with light field. Interlayer excitons in heterobilayers, with layer separation of electron and hole components, feature large electric dipole that enables strong coupling with electric field and exciton-exciton interaction, at the cost that the optical dipole is substantially quenched (by several orders of magnitude). In this letter, we demonstrate the ability to create a new class of excitons in transition metal dichalcogenide (TMD) hetero- and homo-bilayers that combines the advantages of monolayer- and interlayer-excitons, i.e. featuring both large optical dipole and large electric dipole. These excitons consist of an electron that is well confined in an individual layer, and a hole that is well extended in both layers, realized here through the carrier-species specific layer-hybridization controlled through the interplay of rotational, translational, band offset, and valley-spin degrees of freedom. We observe different species of such layer-hybridized valley excitons in different heterobilayer and homobilayer systems, which can be utilized for realizing strongly interacting excitonic/polaritonic gases, as well as optical quantum coherent controls of bidirectional interlayer carrier transfer either with upper conversion or down conversion in energy

Short-Term Efficacy of Laparoscopic Treatment for Colorectal Cancer in Patients with Schistosomiasis Japonica

Introduction. Schistosomiasis is associated with numerous complications such as thrombocytopenia, liver cirrhosis, portal hypertension, and colitis. To the best of our knowledge, the feasibility and outcomes of laparoscopic colorectal surgery in patients with schistosomiasis have not yet been studied. Methods. In this study, the data of 280 patients with colorectal carcinoma along with schistosomiasis japonica infection who underwent laparoscopic or open colorectal surgery were retrospectively analyzed. Preoperative data, operative data, pathological outcomes, postoperative complications, and recovery were compared between patients in the laparoscopic (LAC) and open (OC) groups. Results. There were no significant differences in the preoperative data between the groups. However, fewer postoperative complications, especially severe hypoproteinemia, early postoperative feeding, and shorter postoperative hospital stay, were observed in patients in the LAC group (P<0.001). The mean operative time was higher in the LAC group (180 min versus 158 min; P<0.001), while the mean blood loss was similar (95 mL versus 108 mL; P=0.196) between groups. The mean number of lymph nodes harvested was also similar in both groups (15 versus 16; P=0.133). Conclusion. Laparoscopic surgery for colorectal cancer is safe in patients with schistosomiasis japonica and has better short-term outcomes than open surgery