检索结果-内蒙古大学图书馆

ROSF: Leveraging Information Retrieval and Supervised Learning for Recommending Code Snippets

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Jiang, He Nie, Liming Sun, Zeyi Ren, Zhilei Kong, Weiqiang Zhang, Tao Luo, Xiapu School of Software Dalian University of Technology Dalian China Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province Dalian China State Key Laboratory of Software Engineering Wuhan University Wuhan China Key Laboratory for Ubiquitous Network Service Software of Liaoning Province Dalian China School of Computer Science & Technology Nanjing University of Posts and Telecommunications Nanjing China Department of Computing Hong Kong Polytechnic University Hong Kong Hong Kong

—when implementing unfamiliar programming tasks, developers commonly search code examples and learn usage patterns of APIs from the code examples or reuse them by copy-pasting and modifying. For providing high-quality code examples, previous studies present several methods to recommend code snippets mainly based on information retrieval. In this paper, to provide better recommendation results, we propose ROSF, Recommending cOde Snippets with multi-aspect Features, a novel method combining both information retrieval and supervised learning. In our method, we recommend Top-K code snippets for a given free-form query based on two stages, i.e., coarse-grained searching and fine-grained re-ranking. First, we generate a code snippet candidate set by searching a code snippet corpus using an information retrieval method. Second, we predict probability values of the code snippets for different relevance scores in the candidate set by the learned prediction model from a training set, re-rank these candidate code snippets according to the probability values, and recommend the final results to developers. We conduct several experiments to evaluate our method in a large-scale corpus containing 921,713 real-world code snippets. The results show that ROSF is an effective method for code snippets recommendation and outperforms the-state-of-the-art methods by 20% - 41% in Precision and 13% - 33% in NDCG. Copyright © 2017, The Authors. All rights reserved.

关键词： Supervised learning

A Performance Evaluation of Classification Algorithms for Big Data

学校读者我要写书评

暂无评论

Procedia Computer Science 2017年 122卷 1100-1107页

作者： Mo Hai You Zhang Yuejin Zhang School of Information Central University of Finance and Economics Beijing China Network and Data Security Key Laboratory of Sichuan Province University of Electronic Science and Technology of China Chengdu China School of Information Systems &Management Heinz College Carnegie Mellon University Pittsburgh PA 1521 USA

The performance of two typical classification algorithms in Spark: random forest and naïve bayes are evaluated by using four metrics: classification accuracy, speedup, scaleup and sizeup. Experiments are performed on dataset and clusters of different scale. The results show that: (1) the accuracy of the two algorithms is high; (2) the increase of speedup is not linear. For the dataset with different size, the numbers of nodes is different when the speedup is the maximal; (3) the scaleup of random forest reaches its peak when the number of nodes is 2, and after that the scaleup decreases with the increase of the number of nodes;(4) for random forest, when the number of nodes is 2, the sizeup increases sharply with the increase of the size of dataset, and when the number of nodes is greater than 2, the sizeup increases more slowly with the increase of the size of dataset; for naïve bayes, when the number of nodes is smaller than 6, the sizeup increases with the increase of the size of dataset, when number of nodes is 6 and the size of dataset is larger than that of Sogou_5, the change of the sizeup is not obvious with the increase of the size of dataset.

关键词： Spark Random forest Naïve bayes Classification accuracy Speedup Scaleup Sizeup

Android multi-level system permission management approach

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Luo, Yang Zhang, Qi-Xun Shen, Qing-Ni Liu, Hong-Zhi Wu, Zhong-Hai School of Software and Microelectronics Peking University Beijing100871 China MoE Key Laboratory of Network and Software Assurance Peking University Beijing100871 China Research Laboratory of Service Computing and Big Data Technology Peking University Beijing100871 China

With the expansion of the market share occupied by the Android platform, security issues (especially application security) have become attention focus of researchers. In fact, the existing methods lack the capabilities to manage application permissions without root privilege. This study proposes a dynamic management mechanism of Android application permissions based on security policies. The paper first describes the permissions by security policies, then implementes permission checking code and request evaluation algorithm in Android framework layer. Experimental results indicate that the presented approach succeeds in permission management of Android applications, and its system overhead is low, which makes it an effective method for Android permission management. Copyright © 2017, The Authors. All rights reserved.

关键词： Android (operating system)

Angle-domain doppler pre-compensation for high-mobility OFDM uplink with a massive ULA

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Guo, Wei Zhang, Weile Mu, Pengcheng Gao, Feifei Yao, Bobin MOE Key Lab for Intelligent Networks and Network Security Xi'an Jiaotong University Xi'an China Tsinghua National Laboratory for Information Science and Technology Beijing China School of Electronic and Control Engineering Chang'an University Xi'an China

In this paper, we propose a Doppler pre-compensation scheme for high-mobility orthogonal frequency division multiplexing (OFDM) uplink, where a high-speed terminal transmits signals to the base station (BS). Considering that the time-varying multipath channel consists of multiple Doppler frequency offsets (DFOs) with different angle of departures (AoDs), we propose to perform DFO pre-compensation at the transmitter with a large-scale uniform linear array (ULA). The transmitted signal passes through a beamforming network with high-spatial resolution to produce multiple parallel branches. Each branch transmits signal towards one direction thus it is affected by one dominant DFO when passing over the time-varying channel. Therefore, we can compensate the DFO for each branch at the transmitter previously. Theoretical analysis for the Doppler spread of the equivalent uplink channel is also conducted. It is found that when the number of transmit antennas is sufficiently large, the time-variation of channel can be efficiently suppressed. Therefore, the performance will not degrade significantly if applying the conventional time-invariant channel estimation and equalization methods at the receiver. Simulation results are provided to verify the proposed scheme. Copyright © 2017, The Authors. All rights reserved.

关键词： Frequency allocation

DOA and polarization estimation for non-circular signals in 3-D millimeter wave polarized massive MIMO systems

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Wan, Liangtian Liu, Kaihui Liang, Ying-Chang Zhu, Tong Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province School of Software Dalian University of Technology Dalian116620 China National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Chengdu611731 China National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China Chengdu611731 China School of Electrical and Information Engineering University of Sydney NSW2006 Australia Tianjin Institute of Computing Technology Tianjin300000 China

In this paper, an algorithm of multiple signal classification (MUSIC) is proposed for two-dimensional (2-D) direction-of-arrival (DOA) and polarization estimation of non-circular signal in three-dimensional (3-D) millimeter wave polarized large-scale/massive multiple-input-multiple-output (MIMO) systems. The traditional MUSIC-based algorithms can estimate either the DOA and polarization for circular signal or the DOA for non-circular signal by using spectrum search. By contrast, in the proposed algorithm only the DOA estimation needs spectrum search, and the polarization estimation has a closed-form expression. First, a novel dimension-reduced MUSIC (DR-MUSIC) is proposed for DOA and polarization estimation of circular signal with low computational complexity. Next, based on the quaternion theory, a novel algorithm named quaternion non-circular MUSIC (QNC-MUSIC) is proposed for parameter estimation of non-circular signal with high estimation accuracy. Then based on the DOA estimation result using QNC-MUSIC, the polarization estimation of non-circular signal is acquired by using the closed-form expression of the polarization estimation in DR-MUSIC. In addition, the computational complexity analysis shows that compared with the conventional DOA and polarization estimation algorithms, our proposed QNC-MUSIC and DR-MUSIC have much lower computational complexity, especially when the source number is large. The stochastic Cramér-Rao Bound (CRB) for the estimation of the 2-D DOA and polarization parameters of the non-circular signals is derived as well. Finally, numerical examples are provided to demonstrate that the proposed algorithms can improve the parameter estimation performance when the large-scale/massive MIMO systems are employed. Copyright © 2017, The Authors. All rights reserved.

关键词： MIMO systems

Continuous-variable measurement-device-independent quantum key distribution with virtual photon subtraction

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Zhao, Yijia Zhang, Yichen Xu, Bingjie Yu, Song Guo, Hong State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China State Key Laboratory of Advanced Optical Communication System and Network School of Electronics Engineering and Computer Science Center for Quantum Information Technology Peking University Beijing100871 China Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu610041 China

The method of improving the performance of continuous-variable quantum key distribution protocols by post-selection has been recently proposed and verified. In continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocols, the measurement results are obtained from untrusted third party Charlie. There is still not an effective method of improving CV-MDI QKD by the post-selection with untrusted measurement. We propose a method to improve the performance of coherent-state CV-MDI QKD protocol by virtual photon subtraction via non-Gaussian post-selection. The non-Gaussian post-selection of transmitted data is equivalent to an ideal photon subtraction on the two-mode squeezed vacuum state, which is favorable to enhance the performance of CV-MDI QKD. In CV-MDI QKD protocol with non-Gaussian post-selection, two users select their own data independently. We demonstrate that the optimal performance of the renovated CV-MDI QKD protocol is obtained with the transmitted data only selected by Alice. By setting appropriate parameters of the virtual photon subtraction, the secret key rate and tolerable excess noise are both improved at long transmission distance. The method provides an effective optimization scheme for the application of CV-MDI QKD protocols. Copyright © 2017, The Authors. All rights reserved.

关键词： Quantum cryptography

Robust online matrix factorization for dynamic background subtraction

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Yong, Hongwei Meng, Deyu Zuo, Wangmeng Zhang, Lei School of Mathematics and Statistics Ministry of Education Key Lab of Intelligent Networks and Network Security Xi'an Jiaotong University Shaanxi China School of Computer Science and Technology Harbin Institute of Technology Harbin China Biometrics Research Center Department of Computing Hong Kong Polytechnic University Kowloon Hong Kong

We propose an effective online background subtraction method, which can be robustly applied to practical videos that have variations in both foreground and background. Different from previous methods which often model the foreground as Gaussian or Laplacian distributions, we model the foreground for each frame with a specific mixture of Gaussians (MoG) distribution, which is updated online frame by frame. Particularly, our MoG model in each frame is regularized by the learned foreground/background knowledge in previous frames. This makes our online MoG model highly robust, stable and adaptive to practical foreground and background variations. The proposed model can be formulated as a concise probabilistic MAP model, which can be readily solved by EM algorithm. We further embed an affine transformation operator into the proposed model, which can be automatically adjusted to fit a wide range of video background transformations and make the method more robust to camera movements. With using the sub-sampling technique, the proposed method can be accelerated to execute more than 250 frames per second on average, meeting the requirement of real-time background subtraction for practical video processing tasks. The superiority of the proposed method is substantiated by extensive experiments implemented on synthetic and real videos, as compared with state-of-the-art online and offline background subtraction methods. Copyright © 2017, The Authors. All rights reserved.

关键词： Video signal processing

Construction of One-Gray Weight Codes and Two-Gray Weight Codes over Z4+uZ4

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2016年第5期29卷 1472-1484页

作者： SHI Minjia WANG Dandan GAO Jian WU Bo Key Laboratory of Intelligent Computing & Signal Processing Ministry of Education Anhui University Hefei 230039 China National Mobile Communications Research Laboratory Southeast University Nanjing 210096China School of Mathematical Sciences Anhui University Hefei 230601 China. School of Science Shandong University of Technology Zibo 255091 China State Key Laboratory of Information Security Institute of Information Engineering Chinese Academy of Sciences Bcijing 100093 China

This paper firstly gives some necessary conditions on one-Gray weight linear codes. And then we use these results to construct several classes of one-Gray weight linear codes over Z_4 +uZ_4(u^2=u) with type 16^(k_1)8^(k_2)8^(k_3)4^(k_4)4^(k_5)4^(k_6)2^(k_7)2^(k_8) based on a distance-preserving Gray map from(Z4 + u Z4)n to Z2n4. Secondly, the authors use the similar approach to do works on two-Gray(projective) weight linear codes. Finally, some examples are given to illustrate the construction methods.

关键词： Generator matrix Gray map linear code one-Gray weight code two-Gray weight code

On error linear complexity of new generalized cyclotomic binary sequences of period p2

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Wu, Chenhuang Xu, Chunxiang Chen, Zhixiong Ke, Pinhui School of Computer Science and Engineering University of Electronic Science and Technology of China Chengdu611731 China Provincial Key Laboratory of Applied Mathematics Putian University PutianFujian351100 China Fujian Provincial Key Laboratory of Network Security and Cryptology College of Mathematics and Informatics Fujian Normal University Fuzhou Fujian350117 China

We consider the k-error linear complexity of a new binary sequence of period p2, proposed in the recent paper "New generalized cyclotomic binary sequences of period p2", by Z. Xiao et al., who calculated the linear complexity of the sequences (Designs, Codes and Cryptography, 2017, https://***/10.1007/s10623-017-0408-7). More exactly, we determine the values of k-error linear complexity over F2 for almost k 0 in terms of the theory of Fermat quotients. Results indicate that such sequences have good *** Codes 94A60, 11K45, 11L40 Copyright © 2017, The Authors. All rights reserved.

关键词： Cryptography