Replicas can improve the data reliability in distributed system. However, the traditional algorithms for replica management are based on the assumption that all replicas have the uniform reliability, which is inaccura...Replicas can improve the data reliability in distributed system. However, the traditional algorithms for replica management are based on the assumption that all replicas have the uniform reliability, which is inaccurate in some actual systems. To address such problem, a novel algorithm is proposed based on dynamic programming to manage the number and distribution of replicas in different nodes. By using Markov model, replicas management is organized as a multi-phase process, and the recursion equations are provided. In this algorithm, the heterogeneity of nodes, the expense for maintaining replicas and the engaged space have been considered. Under these restricted conditions, this algorithm realizes high data reliability in a distributed system. The results of case analysis prove the feasibility of the algorithm.展开更多
Multiple earth observing satellites need to communicate with each other to observe plenty of targets on the Earth together. The factors, such as external interference, result in satellite information interaction delay...Multiple earth observing satellites need to communicate with each other to observe plenty of targets on the Earth together. The factors, such as external interference, result in satellite information interaction delays, which is unable to ensure the integrity and timeliness of the information on decision making for satellites. And the optimization of the planning result is affected. Therefore, the effect of communication delay is considered during the multi-satel ite coordinating process. For this problem, firstly, a distributed cooperative optimization problem for multiple satellites in the delayed communication environment is formulized. Secondly, based on both the analysis of the temporal sequence of tasks in a single satellite and the dynamically decoupled characteristics of the multi-satellite system, the environment information of multi-satellite distributed cooperative optimization is constructed on the basis of the directed acyclic graph（DAG）. Then, both a cooperative optimization decision making framework and a model are built according to the decentralized partial observable Markov decision process（DEC-POMDP）. After that, a satellite coordinating strategy aimed at different conditions of communication delay is mainly analyzed, and a unified processing strategy on communication delay is designed. An approximate cooperative optimization algorithm based on simulated annealing is proposed. Finally, the effectiveness and robustness of the method presented in this paper are verified via the simulation.展开更多
地图匹配是智能交通系统中的核心技术之一,旨在将GPS轨迹数据映射至城市路网上,消除定位误差并还原实际行驶路径。随着GPS轨迹数据量的爆炸性增长,传统的基于隐马尔可夫模型(HMM)的地图匹配方法因高计算成本和时序依赖性问题,难以满足...地图匹配是智能交通系统中的核心技术之一,旨在将GPS轨迹数据映射至城市路网上,消除定位误差并还原实际行驶路径。随着GPS轨迹数据量的爆炸性增长,传统的基于隐马尔可夫模型(HMM)的地图匹配方法因高计算成本和时序依赖性问题,难以满足实时处理要求。为此,提出了一种基于轨迹微分段模型的快速地图匹配方法(Micro-Segment Fast Matching,MSFM)。该方法基于滑动窗口机制,将轨迹分解为固定长度的微轨迹段,在分布式计算环境中利用向量化计算方法,在兼顾地图匹配准确性的条件下大幅度提升了计算效率。实验结果表明,在给定的分布式集群环境下,MSFM实现了约110000点/秒的地图匹配速度,比基准算法快约7倍,同时保持了95.86%的匹配准确率。MSFM方法通过改进轨迹数据的存储结构,在高效实时处理大规模轨迹数据方面具有显著的性能优势。展开更多
文摘Replicas can improve the data reliability in distributed system. However, the traditional algorithms for replica management are based on the assumption that all replicas have the uniform reliability, which is inaccurate in some actual systems. To address such problem, a novel algorithm is proposed based on dynamic programming to manage the number and distribution of replicas in different nodes. By using Markov model, replicas management is organized as a multi-phase process, and the recursion equations are provided. In this algorithm, the heterogeneity of nodes, the expense for maintaining replicas and the engaged space have been considered. Under these restricted conditions, this algorithm realizes high data reliability in a distributed system. The results of case analysis prove the feasibility of the algorithm.
基金supported by the National Science Foundation for Young Scholars of China(6130123471401175)
文摘Multiple earth observing satellites need to communicate with each other to observe plenty of targets on the Earth together. The factors, such as external interference, result in satellite information interaction delays, which is unable to ensure the integrity and timeliness of the information on decision making for satellites. And the optimization of the planning result is affected. Therefore, the effect of communication delay is considered during the multi-satel ite coordinating process. For this problem, firstly, a distributed cooperative optimization problem for multiple satellites in the delayed communication environment is formulized. Secondly, based on both the analysis of the temporal sequence of tasks in a single satellite and the dynamically decoupled characteristics of the multi-satellite system, the environment information of multi-satellite distributed cooperative optimization is constructed on the basis of the directed acyclic graph（DAG）. Then, both a cooperative optimization decision making framework and a model are built according to the decentralized partial observable Markov decision process（DEC-POMDP）. After that, a satellite coordinating strategy aimed at different conditions of communication delay is mainly analyzed, and a unified processing strategy on communication delay is designed. An approximate cooperative optimization algorithm based on simulated annealing is proposed. Finally, the effectiveness and robustness of the method presented in this paper are verified via the simulation.
文摘地图匹配是智能交通系统中的核心技术之一,旨在将GPS轨迹数据映射至城市路网上,消除定位误差并还原实际行驶路径。随着GPS轨迹数据量的爆炸性增长,传统的基于隐马尔可夫模型(HMM)的地图匹配方法因高计算成本和时序依赖性问题,难以满足实时处理要求。为此,提出了一种基于轨迹微分段模型的快速地图匹配方法(Micro-Segment Fast Matching,MSFM)。该方法基于滑动窗口机制,将轨迹分解为固定长度的微轨迹段,在分布式计算环境中利用向量化计算方法,在兼顾地图匹配准确性的条件下大幅度提升了计算效率。实验结果表明,在给定的分布式集群环境下,MSFM实现了约110000点/秒的地图匹配速度,比基准算法快约7倍,同时保持了95.86%的匹配准确率。MSFM方法通过改进轨迹数据的存储结构,在高效实时处理大规模轨迹数据方面具有显著的性能优势。
