Catálogo de publicaciones - libros

In this paper, we focus on how to construct an efficient unstructured P2P system. The main contributions of our proposal are two-fold. First, aiming at alleviating the topology mismatch problem between the P2P logical overlay network and the physical underlying network, we proposed a Topology-aware Multi-cluster Overlay (TMO) architecture where peers self-organize into clusters based on network locality. Second, in order to further improve the search efficiency of the TMO architecture, we present two novel index techniques, namely, cluster-index technique and topic-index technique. The two different techniques are highly effective in different application domains in which the TMO architecture is deployed. The simulation results indicate that our proposed schemes are efficient in both resource usage and data retrieval.

Double-loop and 2-circulant networks are widely used in the design and implementation of local area networks and parallel processing architectures. In this paper, we investigate the routing of a message on circulant networks, that is a key to the performance of this network. We would like to transmit 2k packets from a source node to a destination node simultaneously along paths on G(n; ±,±,...,±), where the packet will traverse along the path (1≤ ≤2). In oder for all packets to arrive at the destination node quickly and securely, the path must be node-disjoint from all other paths. For construction of these paths, employing the Hamiltonian Circuit Latin Square(HCLS) we present O() parallel routing algorithm on circulant networks.

Load balancing is one of the best efficient methods for performance improvement of cluster system. Recently, WLC algorithm is used for the load balancing of cluster system. But, the algorithm also has load imbalance between servers, because it uses inaccurate static load status of servers. In this paper, I suggest a more efficient dynamic load balancing algorithm base on various load status information of servers by real time. It shows that load imbalance phenomenon is improved greatly and response time is also improved compare with WLC algorithm.

One major factor that heavily affects the performance of a content distribution network (CDN) is placement of the surrogates. Previous works take a network-centric approach and consider only the network traffic. In this paper, we propose solutions to optimal surrogate placement, taking into consideration both network latency and capacity constraints on the surrogates. For CDNs with a tree topology, an efficient and effective greedy algorithm is proposed which minimizes network traffic while at the same time maximizing system throughput. Simulation results show that the greedy algorithm is far better than the existing optimal placement scheme that makes decisions based solely on network traffic. This suggests that capacity constraints on surrogates or server bottlenecks should be considered when determining surrogate placement, especially when the capacities of CDN servers are limited.

Routing and wavelength assignment (RWA) is a central issue to increase efficiency and reduce cost in Wavelength Division Multiplexing (WDM) optical networks. In this paper, we propose an improved scheme of wavelength assignment of parallel FFT communication pattern on a class of regular optical networks. With our new scheme, the numbers of wavelengths required to realize parallel FFT communication pattern with 2 nodes on WDM linear arrays, rings, 2-D meshes and 2-D tori are , , and respectively, which are about one-third less for linear arrays and meshes, and a half less for rings and tori, than the known results. Our results have a clear significance for applications because FFT represents a common communication pattern shared by a large class of scientific and engineering problems and WDM optical networks as a promising technology in networking has an increasing popularity.

A general-purpose parallel three-list four-table algorithm that can solve a number of knapsack-like NP-complete problems is developed in this paper. Running on an EREW PRAM model, The proposed parallel algorithm can solve this kind of problems of size in (2) time, with (2) shared memory units and (2) processors, and thus its time-space-processor tradeoff is (2 ). The performance analysis and comparisons show that the proposed algorithms are both time and space efficient, and thus is an improved result over the past researches. Since it can break greater variables knapsack-based cryptosystems and watermark, the new algorithm has some cryptanalytic significance.

This paper defines the properties of FDT (Flow Dependence Tail set) and FDH (Flow Dependence Head set), and presents two partitioning methods for finding two parallel regions in two-dimensional solution space. One is the region partitioning method by intersection of FDT and FDH. Another is the region partitioning method by two given equations. Both methods show how to determine whether the intersection of FDT and FDH is empty or not. In the case that FDT does not overlap FDH, we will divide the iteration space into two parallel regions by a line. The iterations within each area can be fully executed in parallel. So, we can find two parallel regions for doubly nested loops with non-uniform dependences for maximizing parallelism.

This paper introduces a new static data dependence constraint, called dependence difference inequality, which can deal with coupled subscripts for multi-dimensional array references. Unlike direction vectors, dependence difference inequalities are related to not only the iteration space for a loop program but also the operation distance between two operations. They are more strict than other methods, and can act as additional constraints to each variable in a linear system on their own or with others. As a result, the solution space for a linear system can be compressed heavily. So long as dependence difference inequalities do not satisfy simultaneously, the loop can be software-pipelined with any initiation interval even if there exists a data dependence between two operations. Meanwhile, by replacing direction vectors with dependence difference inequalities some conservative estimations made by other traditional data dependence analysis approaches can be eliminated.

This paper presents a run-time pointer aliasing disambiguation method for software pipelining techniques. By combining hardware with software, the method is better than run-time checking method or run-time compensation method, which is capable of dealing with irreversible code, and has limited compensation code space without serious rerollability problem. The new method solves pointer aliasing problem efficiently and makes it possible to obtain potential instruction-level parallel speedup. In this paper instruction-level parallel speedups of the new method are analyzed in detail. Three theoretical speedups, i.e., , and , are given, which will be helpful for studying and evaluating instruction-level parallelism of the new method.

Data cube has been playing an essential role in fast OLAP(on-line analytical processing) in many multidimensional data warehouse. We often execute range queries on aggregate cube computed by pre-aggregate technique in MOLAP. For the cube with d dimensions, it can generate 2 cuboids. But in a high-dimensional data warehouse (such as the applications of bioinformatics and statistical analysis, etc.), we build all these cuboids and their indices and full materialized the data cube impossibly. In this paper, we propose a multi-dimensional hierarchical fragmentation of the fact table based on dimension hierarchical encoding. This method partition the high dimensional data cube into shell mini-cubes. Using dimension hierarchical encoding and pre-aggregated results, OLAP queries are computed online by dynamically constructing cuboids from the fragment data cubes. Such an approach permits a significant reduction of processing and I/O overhead for many queries by restricting the number of fragments to be processed for both the fact table and bitmap encoding data. This method also supports parallel I/O and parallel processing as well as load balancing for disks and processors. We have compared the methods of our parallel method with the other existed ones such as partial cube by experiment. The analytical and experimental results show that the method of our parallel method proposed in this paper is more efficient than the other existed ones.