In this paper, a new optimum input encoding algorithm with m-out-of-2m code which is called Half-Hot Code is presented. By applying Half-Hot Code to the input encoding in PLA-based digital system, the logic functions of the system turn out to be unate functions, thus, the number of bit-lines of PLA may be reduced. The proposed method further reduces the number of product-lines of PLA optimally. In this code assignment procedure, computed Boolean subspaces satisfying suggeset two conditions are assigned to each partitioned subset of digital input variables which are obtained by disjoint minimization or other techniques. As an experiment to evaluate the method, the state assignment for finite state machines of two-lavel implementation is considered. Specifically, the proposed Half-Hot Code assignment is compared with arbitrary Half-Hot Code assignment. The results show that the optimum encoding is superior to an arbitrary assignment up to about 24% in the number of product-lines of PLA.

This paper proposes a masked data transferring method for the write-back controlled disk cache system employing a fixed-length recording disk drive, enabling data transfer of discontinuous sectors on the same track between the cache and the disk. This paper also evaluates the method. In write-back controlled disk cache sytems, random write requests cause dirty data (write-pending data on a cache) on discontinuous areas on the cache. It is likely that several sectors on the same track become dirty. These dirty sectors must be written onto the disk according to the cache management scheme. In conventional data transferring methods between a disk cache and a disk drive, plural sectors can be transferred in one single operation when the sectors are adjacent, but discrete sectors must be transferred by individual operations. In the methods, an address of the head sector and number of sectors to be transferred are given to the transfer unit. For example, when two sectors on the same track are located closely but not adjacently, and data transfer is requested for those two sectors, the transfer operation for the second sector must be prepared after the first transfer had completed and before the second sector arrives under the disk head. Although the time for the head to pass by the uninterested sector is often too short for the software overhead for the first transfer to be completed and the second transfer to be prepared, which leads to an unwanted extra rotation of the disk. With the masked transferring method proposed in this paper, the micro program creates a bit-map specifying the target sectors to be transferred and passes it to the data transfer unit, enabling to transfer the discontinuous sectors without latency. The method was evaluated using OLTP warkloads. Results show an improvement in random I/O throughput of between 8% and 27%. The masked transferring method is adopted in Hitachi's A-6521 disk subsytems, shipped since December 1993.

We propose a new high-performance message router for k-ary n-cube multicomputer systems, called the Tokky router. The router utilizes a small number of queues at the outputs of its communication ports to allow fully adaptive routing, misrouting to prevent deadlocks and randomization to prevent livelock. Uncongeste network performance is improved by the inclusion of the packet expressway. Accurate models are developed to predict the switch and buffer performance of routers for varying radix and dimension and these models can be used in the design of routers for networks other than those investigated here. The simulated performance of the router exceeds that of published results for oblivious routers and is equal to or exceeds those reported for other adaptive routers. These performance predictions are especially encouraging when the simplicity of the control structures required to implement the router are taken into consideration.

In the program development process, it is ofren necessary for programmers to know the differences between two programs, or two different versions of a program. Since programs have structures such as iteration statement and selection statement, applying text-based tools such as UNIX diff to identify the differences may produce unsatisfactory results. In this paper, we exploit a tree as the internal representation of a program, obtain the mapping between two trees and display the program differences visually based on the mapping and pretty-printing technique so that the structural differences can be identified immediately.

To advance the productivity of software for communication systems, specification development is important as well as the implementation of the software. For this reason, we developed a specification description language HSC (Hierarchical Sequence Chart), which is useful during the early stage of specification development. The features of HDC are: a) HSC is suitable for a top-down style of specification development, b) specifications can be described by HSC with clear visibility of the whole system, and c) the specification development based on specification reuse is possible. The specification development of communication systems can be divided into three processes: specification acquisition, specification description and specification verification. In this paper we will concentrate on specification acquisition part. We will use the language developed by us, HSC, which is very suitable for this purpose. In this work, we noted that hierarchical structure is the characteristic feature of communication software. As the language HSC has inherent hierarchy and modularity, we conjectured it to be suitable for specifying the requirements of communication software. Efficient reuse of components is accomplished by using CBR technique. Furthermore, we propose a specification acquisition method AOBA, and implemented a support environment for it, called AOBA system, using the CBR tool ART-IM. We experimeted with the descriptions of communication systems, for example, the descriptions of services in a telephone system using AOBA System. Through these experiments, the effectiveness of AOBA and AOBA System is ensured.

The integration of both real-time systems and fault-tolerant systems has been emerged as one of the greatest challenges of this decade. It is called a responsive system, which has the objective to optimeze both timeliness and reliability. The performance measure in responsive systems is responsiveness that tells how probable a system executes correctly on time with faults occurred. While there have been some achievements in communication protocols and specification, we believe that scheduling problems in responsive systems are not understood deeply and sufficiently, yet. In this paper, we discuss the scheduling problem in responsive systems. At first, we investigate the issues in the scheduling and propose the precise definition of the responsiveness. We also suggest a scheduling algorithm called Responsive Earliest Deadline First (REDF) for preemptive aperiodic tasks in a uniprocessor system. We show that REDF is optimal to obtain the maximum responsiveness, and the time complexity is analyzed to be (N 2^N). By illustrating a contradictory example, it is shown that REDF can be enhanced if a constraint on tasks is released.

Active net is a deformable model which utilizes the network analogy of a physical region. In the model, the region of a target is detected by minimizing the energy defined for the sample points of the model. The region of the target is extracted using fixed network topology in the orginally proposed algorithm. In this paper, we introduce the network reconfiguration mechanisms such as tearing and division to realize multiple objects detection and complex object detecion. The introduced algorithm dynamically unlinks the arcs of the network when their strain value exceeds predefined threshold level. In the method, we propose a new image energy which improves the position sensitivity of edges without increasing computation cost. Experimental results for images taken by video camera show the validity of our approach.

The classification of remotely sensed multispectral data using classical statistical methods has been worked on for several decades. Recently there have been many new developments in neural network (NN) research, and many new applications have been studied. It is well known that NN approaches have the ability to classify without assuming a distribution. We have proposed an NN model to combine the spectral and spacial information of a LANDSAT TM image. In this paper, we apply the NN approach with a normalization method to classify multi-temporal LANDSAT TM images in order to investigate the robustness of our approach. From our experiments, we have confirmed that our approach is more effective for the classification of multi-temporal data than the original NN approach and maximum likelihood approach.

Theoretically, corresponding pairs of feature points between two stereo images can determine their 3-D locations uniquely by triangulation. In the presence of noise, however, corresponding feature points may not satisfy the epipolar equation exactly, so we must first correct the corresponding pairs so as to satisfy the epipolar equation. In this paper, we present an optimal correction method based on a statistical model of image noise. Our method allows us to evaluate the magnitude of image noise a posteriori and compute the covariance matrix of each of the reconstructed 3-D points. We demonstrate the effectiveness of our method by doing numerical simulation and real-image experiments.

Dynamic Programming based elastic pattern matching method called Branched Reference Rubber String Matching was investigated. As in Rubber String Matching, the reference pattern is represented as a sequence of direction specified vectors and the input pattern as two dimensional dot pattern. In order to improve the coping of topological variations in input pattern, the reference patterns allow partial pattern alternatives and misses. Effect on the recognition time is almost negligible. Experimental results show the effectiveness of the proposed algorithm.

A new algorithm for multiple-precision modular multiplication is proposed. It is fast and uses a small amount of main memory, and hence, is useful for application of a public-key cryptosystem to small computers, such as card computers.

The overall performance of a shared-memory, common bus multiprocesser system can be seriously affected by useless coherence-related actions. This occurs, in particular, when a private data block of a process becomes resident in more than one cache as a consequence of the migration of the owner process. We introduce a hardware solution to eliminate these useless shared copies, and show how this technique can be applied to a specific coherence protocol. Two extreme workload conditions are properly selected to evaluate the performance of a multiprocessor system.

We present that event-transition diagrams are useful to analyze event concurrent response visually. Event-transition diagrams are dual for state-transition diagrams in graph theory. As an example of an usage of an event-transition diagram, a simple model of a railroad crossing is presented.

We present basic strategies for memory-restricted forgetting mechanisms of cases and propose a forgetting strategy which is a combination of the basic strategies. The effectivness of the proposed strategy for improving the performance of case-based reasoning systems is demonstrated through simulations in the electric power systems.