• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1329-1338
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• 2011

This paper proposes an algorithm and hardware architecture for a broadcast communication which has the worst bottleneck among multiprocessor using distributed memory architectures. In conventional systems, collective communication is converted into point-to-point communications by MPI library cell without considering the state of communication port of each processing node which represents the processing node is in busy state or free state. If conflicting point-to-point communication occurs during broadcast communication, the transmitting speed for broadcast communication is decreased. Thus, this paper proposed an algorithm which determines the order of point-to-point communications for broadcast communication according to the state of each processing node. According to the state of each processing node, the proposed algorithm decreases total broadcast communication time by transmitting message preferentially to the processing node with communication port in free state. The proposed MPI unit for broadcast communication is evaluated by modeling it with systemC. In addition, it achieved a highly improved performance for broadcast communication up to 78% with 16 nodes. This result shows the proposed algorithm is useful to improving total performance of MPSoC.

• The KIPS Transactions:PartA
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• v.12A no.1 s.91
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• pp.41-52
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• 2005

Memory reference instruction caused by cache miss is the critical factor that limits the processing power of processor. Cache prefetching technique is an effective way to reduce the latency due to memory access. However, excessively aggressive prefetch leads to cache pollution and finally to cancel out the advantage of prefetch. In this study, an active prefetch filtering scheme is introduced which dynamically decides whether to commence prefetching after referring a filtering table to reduce the cache pollution due to unnecessary prefetches. For the precision filtering, an evicted address referencing scheme has been proposed where the filter directly compares the current prefetch address with previous unnecessary prefetch addresses stored in filtering table. Moreover, a small sized exclusive prefetch cache has been introduced to increase the amount of eviction of unnecessarily prefetched addresses to enhance the accuracy of dynamic filtering. The exclusive prefetch cache also prevents useful demand data from being pushed out by prefetched data, while the evicted address direct referencing scheme enables the prefetch cache to keep most of useful prefetch data within its small size. Experimental results from commonly used general and multimedia benchmarks show that the average cache miss ratio has been decreased by $13.3{\%}$ by virtue of enhanced filtering accuracy compared with conventional schemes.

• Journal of Intelligence and Information Systems
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• v.18 no.3
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• pp.35-51
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• 2012

Cloud computing is internet-based computing where computing resources are offered over the Internet as scalable and on-demand services. In particular, in case a number of various cloud services emerge in accordance with development of internet and mobile technology, to select and provide services with which service users satisfy is one of the important issues. Most of previous works show the limitation in the degree of user satisfaction because they are based on so called concept similarity in relation to user requirements or are lack of versatility of user preferences. This paper presents cloud service selection reasoning which can be applied to the general cloud service environments including a variety of computing resource services, not limited to web services. In relation to the service environments, there are two kinds of services: atomic service and composite service. An atomic service consists of service attributes which represent the characteristics of service such as functionality, performance, or specification. A composite service can be created by composition of atomic services and other composite services. Therefore, a composite service inherits attributes of component services. On the other hand, the main participants in providing with cloud services are service users, service suppliers, and service operators. Service suppliers can register services autonomously or in accordance with the strategic collaboration with service operators. Service users submit request queries including service name and requirements to the service management system. The service management system consists of a query processor for processing user queries, a registration manager for service registration, and a selection engine for service selection reasoning. In order to enhance the degree of user satisfaction, our reasoning stands on basis of the degree of conformance to user requirements of service attributes in terms of functionality, performance, and specification of service attributes, instead of concept similarity as in ontology-based reasoning. For this we introduce so called a service attribute graph (SAG) which is generated by considering the inclusion relationship among instances of a service attribute from several perspectives like functionality, performance, and specification. Hence, SAG is a directed graph which shows the inclusion relationships among attribute instances. Since the degree of conformance is very close to the inclusion relationship, we can say the acceptability of services depends on the closeness of inclusion relationship among corresponding attribute instances. That is, the high closeness implies the high acceptability because the degree of closeness reflects the degree of conformance among attributes instances. The degree of closeness is proportional to the path length between two vertex in SAG. The shorter path length means more close inclusion relationship than longer path length, which implies the higher degree of conformance. In addition to acceptability, in this paper, other user preferences such as priority for attributes and mandatary options are reflected for the variety of user requirements. Furthermore, to consider various types of attribute like character, number, and boolean also helps to support the variety of user requirements. Finally, according to service value to price cloud services are rated and recommended to users. One of the significances of this paper is the first try to present a graph-based selection reasoning unlike other works, while considering various user preferences in relation with service attributes.