KEYWORDS: Internet, Computer simulations, Cell phones, Mobile communications, Defense and security, Detection and tracking algorithms, Telecommunications, Personal digital assistants, Local area networks, Wireless communications
In the wired Internet, it is common practice to use Web caching to reduce network utilization and improve access time to a Web page. Mobile users introduce new variables in the communication process due to the fact that a user may dynamically change its contact point within the network, accessing the Web server through a different path, which may not have access to cached pages. In hostile environments such as domestic catastrophic emergencies, field units must have a higher priority to significant information available through Web servers, requiring lower response times and reliable access via Internet enabled cell phones. In foreign lands, specific infrastructure must be implemented and activated, which requires extensive work currently being researched by defense contractors. In domestic situations, the infrastructure exists and must be equipped to provide the necessary priority to civil defense personnel. This study discusses mechanisms used in Web caching and suggests features that should be added to current cache management algorithms to provide the necessary priority, including the use of standard protocol commands to identify cacheable information and establishment of priority and aging policies to control the length of time data should be maintained in the cache.
Image signal processing depends on computation intensive programs, which include the repetition of sequences of operations coded as nested loops. An effective technique in increasing the computing performance of such applications is the design and use of Application Specific Integrated Circuits using loop transformation techniques, and in particular, multi-dimensional (MD) retiming. The MD-retiming method improves the instruction-level parallelism of uniform loops. While many have written about the multi-dimensional retiming technique, no results have been published on the possible limitations of its application. This paper presents an analysis of that technique and its constraints when applied to nested loops with known index bounds, such as those found in two and three dimensional image processing.
Multi-dimensional applications, such as image processing and seismic analysis, usually require the high computer performance obtained from the implementation of Application Specific Integrated Circuits (ASICs). The critical sections of such applications consist of nested loops with the possibility of embedded conditional branch instructions. Current commercial systems use branch predication techniques, which can also be applied in the design of ASIC systems. Those techniques utilize predicate registers to control the validity of computed results. The optimized design and allocation of such registers becomes then a significant factor in the performance of the system. By using branch prediction to transform control dependencies in data dependencies, the application of a multi-dimensional retiming to an MDFG permit the iterations of the original loop body to be naturally overlapped, making the existent parallelism explicit. Based on the retiming information, predicate registers are designed as shift registers that allow the correct execution of the filter function.
Image enhancement applications are highly dependent on the efficiency of edge detection techniques. Most of these techniques have a time complexity of O(n2) where the picture has size n X n. The use of more advanced algorithms can substantially reduce this requirement, improving the computational performance of the application. This paper presents a new method, named GALE, which combines the random search mechanisms of Genetic Algorithms with linear time methods. The resulting edge detection process approaches linear time complexity as demonstrated in the experiments also reported here. The Genetic Algorithm is constructed by utilizing a fitness measurement which is proportional to a directional gradient to select picture windows and establishes candidate pairs of points which bracket an edge. Such areas are then investigated by using near-neighbor linear techniques and the Sobel number for edge identification and detection. The linear technique procedures are built in such a way that the use of other fitness functions, such as the Sombrero operator, instead of the Sobel number are easily implemented and activated. The paper begins by discussing related work in this area, following by the description of the basic concepts of Genetic Algorithms required for this solution. A detailed view of the linear search algorithm is then presented, followed by a report on some experiments conducted in a controlled environment. Theoretical results are used to support the evidence of the time complexity and correctness of this new method. In addition, the experimental results show the improved performance of this method.
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