Recently, as microprocessors have become greatly enhanced and the needs for parallel computation have increased, relatively cheaper PC clusters have come available and have proved to be popular in general purposes [13�C16]. Computers in a PC cluster are little different from ordinary personal computers or workstations, and the processor in each computer can interact with others by a message passing protocol such as MPI (Message Passing Interface) [17] or PVM (Parallel Virtual Machine) [18], through either an Ethernet or other higher-speed inter-connections. A general PC cluster consists of a master node, several slave nodes and network devices. A master node takes the role of the user interface, data input/output/distribution and control of slave nodes, and the slave nodes are responsible for data processing.
In this study, we used a PC cluster to evaluate the proposed parallel algorithm.2.2.2. Performance Evaluation(1) SpeedupThe speedup Sp(n) is defined as the ratio of the time required by an optimal sequential algorithm using one processor versus that required by a parallel algorithm, using p processors, processing input data of size n [18]. Ideally, Sp(n) should be p, but does not attain p, owing to overhead such as communication between processors and other delays:Sp(n)=T(n)Tp(n)(1)where T(n) is the time complexit
Monitoring the environmental conditions of places like museums, buildings, or archaeological sites requires wide nets of different sensing Drug_discovery devices [1]. Likewise, there should be different visual quality requirements for video sensor applications.
Most security systems, with their transmission bandwidth and computing power both being sufficient, emphasize their automatic recognition techniques. In some situations such as baby monitors and intruder avoidance, the decision function of security systems can be shifted to the concerned human if the video information can be provided inexpensively. For instance, the mother does not need to know the details of her baby��s face, but the general behavior of her baby, like whether it has fallen down from the bed. With the possibility of very small displays on wrist-watch type cellphones, the low visual quality is tolerated with the convenient help of human decision-making. Therefore, the promotion of mobile video communication under very low data rate such as below 10 Kbps is appropriate now.Video coding with a bit rate below 10 Kbps has not been considered as a practical application in commercial communication systems because speech transmission is conventionally the major application for the real time communication. As a result, a user in the present multiple access system is usually assigned a fixed conceptual channel with the bit rate of speech signal.