In many parallel programs, run-time data redistribution is usually required to enhance data locality and reduce remote memory access on the distributed memory multicomputers. Research on data redistribution algorithms has recently matured. The time required to generate data sets and processor sets is much lesser than before. Therefore, packing/unpacking has become a relatively high cost in redistribution. In this paper, we present methods to perform BLOCK-CYCLIC(s) to BLOCK-CYCLIC(t) redistribution, using MPI user-defined datatypes. This method reduces the required memory buffers and avoids unnecessary movement of data. Theoretical models are presented to determine the best method for redistribution. The methods were implemented on an IBM SP2 parallel machine to evaluate the performance of the proposed methods. The experimental results indicate that this approach can clearly improve the redistribution in most cases.

In many parallel programs, run-time array redistribution is usually required to enhance data locality and reduce remote memory access on the distributed memory multicomputers. In general, array distribution can be classified into regular distribution and irregular distribution according to the distribution fashion. Many methods for performing regular array redistribution have been presented in the literature. However, for the heterogeneous computation environment, irregular array redistributions can be used to adjust data assignment at run-time. In this paper, an Essential Cycle Calculation method for unequal block sizes array redistribution is presented. In the ECC method, a processor first computes the source/destination processor/data sets of array elements in the first essential cycle of the local array it owns. From the source/destination processor/data sets of array elements in the first essential cycle, we can construct packing/unpacking pattern tables. Since each essential cycle has the same communication pattern, based on the packing/unpacking pattern tables, a processor can pack/unpack array elements efficiently. To evaluate the performance of the ECC method, we have implemented this method on an IBM SP2 parallel machine and compare it with the Sequence method. The cost models for these methods are also presented. The experimental results show that the ECC method greatly outperforms the Sequence method for all test samples.

Replication to mask the effects of failures is a basic technique for improving reliability of a file system. Consistency control protocols are implemented to ensure the consistency among these replicas. The native token-based mechanism which merely sequences the distributed requests suffered from the poor system utilization due to the lack of dependence checking between writes and management of out-of-ordered requests. Hence, in this paper, by utilizing the idempotent property of NFS and executing ahead most of independent WRITE requests, the new consistency control scheme is proposed to improve the performance of operations and failure recovery. Finally, a numeric case shows the efficiency of the new scheme.

Over the past few years, there has been significant interest in content-aware routing that use the information found in the payload of packets to provide intelligent request distribution. As these content-aware routing mechanisms have become an increasingly important building block for Internet service providers, the network behavior and effectiveness of such mechanisms are unclear. In this paper we analyze the network dynamic of a busy Web site with the content-aware routing mechanism. We find that some unique characteristics of Web traffic may limit the effectiveness of the content-aware switching. Based on these observations, we also propose solutions to remedy these deficiencies.

The development of an efficient detection mechanism to determine malicious network traffic has been a critical research topic in the field of network security in recent years. This study implemented an intrusion-detection system (IDS) based on a machine learning algorithm to periodically convert and analyze real network traffic in the campus environment in almost real time. The focuses of this study are on determining how to improve the detection rate of an IDS and how to detect more non-well-known port attacks apart from the traditional rule-based system. Four new features are used to increase the discriminant accuracy. In addition, an algorithm for balancing the data set was used to construct the training data set, which can also enable the learning model to more accurately reflect situations in real environment.

Adapting to the structure of 2-D H-Transform, this paper proposes a novel wavelet domain half-pixel motion compensation algorithm HMRME (Half-pixel Multi-Resolution Motion Estimation). The primary objective of this study is the reduction of the aliasing effect caused by the down-sampling in the wavelet transform under the complexity constraints. The conventional multi-resolution motion estimation scheme can be combined with the half-pixel interpolation method to generate a new high-performance wavelet video codec. The preliminary results show that the performance of HMRME rises above its counterparts, the Multi-Resolution Motion Estimation (MRME) and the Adaptive Multi-Resolution Motion Estimation (AMRME).

The explosive growth of the Web contents has led to increasing attention on two major challenges: scalability and high availability of network file system. In this paper, based on our previous reports, we introduced the concept of intermediate file handle to cover the heterogeneity of file system and proposed a new data consistency scheme to reduce the overhead of write request in the reliable network file system. In addition, we also proposed a simple load-sharing mechanism for NFS client to switch to a lightly-load server in order to improve the response time of READ requests. With such an approach, NFS Clients are always active. They issued their requests and waited the corresponding replies. Finally, we analyzed the new data consistency scheme. It shows truly that the scheme is able to improve the performance of our network file system

In this paper, a new Hierarchical Sum of Double Difference metric, HSDD, is introduced. It is shown, as opposed to conventional Sum of Absolute Difference (SAD) metric, how this zerotree coding aware metric can jointly constrain the motion vector searching for both temporal and spatial (quad-tree) directions under multiresolution motion estimation framework. The reward from the temporal-spatial co-optimization concept of HSDD is that fewer bits are spent later for describing the isolated zeros. The embedded wavelet video coder using HSDD metric was tested with a set of video sequences and the compression performance seems to be promising.