18255542
A new method to obtain the shift-table in Boyer-Moore’s string matching algorithm
The Boyer-Moore algorithm uses two pre-computed tables for searching a string: skip, which utilizes the occurrence heuristic of symbols in a pattern, and shift, which utilizes the match heuristic of the pattern. Researchers have pointed out that the difficulty of understanding the computation of the shift table has hindered utilization of the algorithm in a wider range of applications. This paper describes an alternative way to compute the shift table. We believe that the new method is more intuitive and straightforward both conceptually and logically than the original method, and thus, easier to understand and to implement. Also, the new method has O(m) complexity in both required space and time for a pattern of length m. Therefore, it preserves the high performance of the Boyer-Moore algorithm.
14617194
Effects of Suffix Repetition Rates of a String on the Performance of String Matching Algorithms
The highly efficient Boyer-Moore’s string matching algorithm utilizes information on multi-occurrences of string suffixes in a pattern string to avoid backtracks in searching the pattern string. One hypothesis is that Boyer-Moore’s algorithm even benefits more from highly self-repetitive patterns. In this paper, the author studies how multi-occurrences of string suffixes affect the performance of the Boyer-Moore’s algorithm as well as some other well known string search algorithms. The paper introduces a new concept of suffix repetition rate (SRR) to measure how frequently the suffixes of a string occur inside of the string. Using this measurement, experiments with several thousands patterns over the entire range of SRRs have been carried out, and the results show that increasing of SRR on pattern strings does not improve the performance of a searching algorithm in terms of efficiency.
18718248
It is time for a computer application degree
Contemporary computer technology has spread computing activity to almost every field. The computing industry's need for application software developers who have not only proficient programming skills but also a good understanding of subjects in a specific application field has grown rapidly. Continuing to use existing degree programs in computer science to train expected application software developers would not only be a disservice to students but also hamper the further development of computer science programs themselves. Thus, a new degree program is called for in the sub-discipline of computer applications.
33302534
A space-efficient algorithm for sequence alignment with inversions and reversals
A dynamic programming algorithm to find an optimal alignment for a pair of DNA sequences has been described by Schoniger and Waterman. The alignments use not only substitutions, insertions, and deletions of single nucleotides, but also inversions, which are the reversed complements, of substrings of the sequences. With the restriction that the inversions are pairwise non-intersecting, their proposed algorithm runs in O(n2m2) time and consumes O(n2m2) space, where n and m are the lengths of the input sequences, respectively. We develop a space-efficient algorithm to compute such an optimal alignment which consumes only O(nm) space within the same amount of time. Our algorithm enables the computation for a pair of DNA sequences of length up to 10,000 to be carried out on an ordinary desktop computer. Simulation study is conducted to verify some biological facts about gene shuffling across species.
41505059
Distributed Computation in Local Area Networks of Workstations
This paper describes the performance analysis of the local area network (LAN) of workstations for distributed computing applications. Several application programs represented in a task graph format are scheduled by the user workstation (master) for parallel execution in the idle or lightly loaded processors (slaves) in LAN. The partial results are collected by the master station to synchronize the operation of slave nodes. The system performance is characterized by the network speedup considering scheduling time, network load and size, communication time, TCP/IP communication overhead, task execution, and synchronization time. The sequential and parallel execution times and the performance degradation factors were measured during the implementation for various network loads. The measurement values and theoretical results have shown that the system performance is degraded mostly by the TCP/IP overhead (0.2 s), the network size, and the network load.
9019882
Intrusion Detection in Homogeneous and Heterogeneous Wireless Sensor Networks
Intrusion detection in Wireless Sensor Network (WSN) is of practical interest in many applications such as detecting an intruder in a battlefield. The intrusion detection is defined as a mechanism for a WSN to detect the existence of inappropriate, incorrect, or anomalous moving attackers. For this purpose, it is a fundamental issue to characterize the WSN parameters such as node density and sensing range in terms of a desirable detection probability. In this paper, we consider this issue according to two WSN models: homogeneous and heterogeneous WSN. Furthermore, we derive the detection probability by considering two sensing models: single-sensing detection and multiple-sensing detection. In addition, we discuss the network connectivity and broadcast reachability, which are necessary conditions to ensure the corresponding detection probability in a WSN. Our simulation results validate the analytical values for both homogeneous and heterogeneous WSNs.
32478144
Experience from a real life query optimizer
DB2 is a major relational database system on IBM main frames, it has over six thousand licenses over the world to support a very large number of major applications for customer business, Optimizer in DB2 is a critical component for the query processing, it inherited system R technologies and has been improved in very many aspects from numerous valuable real life experiences on customer applications. The major DB2 optimizer enhancements will be discussed with the backgrounds and examples. A wish list for future enhancements as well as some trend and direction of DB2 optimizer will also be discussed.
7931157
A Heuristic Approach to Reconstruct Triangle Mesh from Unorganized Point Cloud
A heuristic algorithm was presented to reconstruct triangle mesh from unorganized point cloud, and a new error evaluation rule was presented to measure the reconstruction errors. The triangle meshes were reconstructed through two phases of mesh growing based on different strategies, where regions with high point density usually grow at the first phase and the remaining regions grow later. In each phase of mesh growing, the smoothest regions always grow firstly and then largely avoid errors emerging in sharp regions. The reformative best point selection method can improve the topology and geometry quality of the reconstructed meshes. The presented error estimation was inspired by the level of detail model and was also can be used in other region grow reconstruction approaches. Experiments show that the algorithm is efficient and effective.