With the expansion of the areas of database applications, the amount of data processed has become gigantic, and the demand for faster database systems has increasingly intensified. Thus, many efforts have been expende...
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With the expansion of the areas of database applications, the amount of data processed has become gigantic, and the demand for faster database systems has increasingly intensified. Thus, many efforts have been expended to execute database operations more efficiently using special hardware. However, for the cases in which mass-produced LSI cannot be used, cost has become excessive, and replacement methods have been sought. Vector processors have powerful pipeline operators and large-capacity main memories and have rapidly spread in recent years. In this paper, algorithms for relational database operations suitable for vector processors showing the characteristics of vector processors sufficiently are presented. This algorithm is based on the hash method, which is highly efficient when the capacity of the main memory is large, and it is shown that a rate of acceleration more than 10 times the average is obtained for representative relational database operations when this algorithm is executed on a vector processor.
Micro kernel architecture is widely used in the design of operating systems. However, traditional micro kernels are not easily extensible and so are not very flexible. For example, the granularity of kernel functions ...
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Micro kernel architecture is widely used in the design of operating systems. However, traditional micro kernels are not easily extensible and so are not very flexible. For example, the granularity of kernel functions does not accord with the users' needs. Moreover, users cannot customize kernel functions easily. Another problem of micro kernels is that system performance is poor due to the overhead of switching address spaces and due to the increased interprocess communication in micro kernels. To address these problems, we have designed and implemented the Lavender micro kernel. Lavender is a micro kernel which can be customized according to application-specific requirements. In order to reduce kernel overhead due to switching address spaces and interprocess communication, Lavender provides users with functionality for process groups and for resident address space. By means of this functionality, the overhead of interprocess procedure calls is reduced to about one-fifth that of other micro kernels. In this paper, the structure and features of Lavender are described. Furthermore, a performance evaluation of process groups and resident address space is presented and the effectiveness of Lavender is discussed.
We present a method of test generation for acyclic sequential circuits with hold registers. A complete (100% fault efficiency) test sequence for an acyclic sequential circuit can be obtained by applying a combinationa...
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We present a method of test generation for acyclic sequential circuits with hold registers. A complete (100% fault efficiency) test sequence for an acyclic sequential circuit can be obtained by applying a combinational test generator to all the maximal time-expansion models (TEMs) of the circuit. We propose a class of acyclic sequential circuits for which the number of maximal TEMs is one, i.e., the maximum TEM exists. For a circuit in the class, test generation can be performed by using only the maximum TEM. The proposed class of sequential circuits with the maximum TEM properly includes several known classes of acyclic sequential circuits such as balanced structures and acyclic sequential circuits without hold registers for which test generation can also be performed by using a combinational test generator. Therefore, in general, the hardware overhead for partial scan based on the proposed structure is smaller than that based on balanced or acyclic sequential structure without hold registers.
This paper reports on an on-going project undertaken within the University of Rome at Tor Vergata to automate the business processes of a class of administrative organizations. The experience gained and the lessons le...
The suffix array is a string-indexing structure and a memory efficient alternative to the suffix tree. It has many advantages for text processing. We propose an efficient algorithm for sorting suffixes. We call this a...
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The suffix array is a string-indexing structure and a memory efficient alternative to the suffix tree. It has many advantages for text processing. We propose an efficient algorithm for sorting suffixes. We call this a...
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The suffix array is a string-indexing structure and a memory efficient alternative to the suffix tree. It has many advantages for text processing. We propose an efficient algorithm for sorting suffixes. We call this algorithm the two-stage suffix sort. One of our ideas is to exploit the specific relationships between adjacent suffixes. Our algorithm makes it possible to use the suffix array for much larger texts and suggests new areas of application. Our experiments on several text data sets (including 514-MB Japanese newspapers) demonstrate that our algorithm is 4.5 to 6.9 times faster than Quicksort, and 2.5 to 3.6 times faster than K. Sadakane's (1998) algorithm, which is considered to be the fastest algorithm in previous work.
The LMS algorithm forms the core of a number of adaptive control schemes. It has on one hand provided certain degree of robustness to these algorithms but on the other hand its convergence rate is notoriously slow. We...
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The LMS algorithm forms the core of a number of adaptive control schemes. It has on one hand provided certain degree of robustness to these algorithms but on the other hand its convergence rate is notoriously slow. We propose a method to initialize the LMS algorithm which dramatically shortens its adaptation period. We also prove that under certain condition this initialization can be computed without explicit knowledge of either the reference or noise spectrum. Although the work is illustrated using the filtered-X scheme, this idea can also be applied to other similar schemes. Two successful experiments starting from black-box identification to real-time control have verified the effectiveness of this idea.
This paper considers an optimization problem of a 3-dimensional truss whose vibration is controlled in the case of sensor/actuator collocation. The design variables are cross sectional areas of truss members and locat...
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This paper considers an optimization problem of a 3-dimensional truss whose vibration is controlled in the case of sensor/actuator collocation. The design variables are cross sectional areas of truss members and locations of the collocated sensors/actuators. The problem has three objectives, the structural weight, the function that represents the influence of the initial state of the system and the number of sensors/actuators. By minimizing the second objective, we can suppress the vibration to some degree. Moreover, in this paper, we consider the uncertainty of the initial state of the system which is dependent on the initial loading conditions. We treat these three objectives by the weighing method for multiobjective problem. The optimization is carried out by the use of Genetic Algorithm. It is shown through numerical simulation that the improvement of the vibration suppression is accomplished by the small control input for the structure designed by the present formulation.
The paper describes a subject called softwareengineering Practise, which introduces softwareengineering concepts to students in a generalist computing degree. The course has three aims: to establish a foundation of ...
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The paper describes a subject called softwareengineering Practise, which introduces softwareengineering concepts to students in a generalist computing degree. The course has three aims: to establish a foundation of good practice which will form the basis for a personal software improvement process in subsequent studies and in professional life; to introduce object oriented design in a context firmly embedded in softwareengineering; and to give students a taste of working in groups on a reasonably large project. The success of this course is due to the way in which the object oriented design, the softwareengineering process aspects and the project work so well together to bring the concepts associated with each part of the course to life and to reinforce each other in a relatively realistic context. Other aspects, which contribute to the success of the course, such as the team approach to course management, individual student assessment, and choice of development environment, are also highlighted.
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