Kentaro Shimizu

A performance comparison of adaptive and static load balancing in heterogeneous distributed systems

This paper focuses on using simulation to compare the performances of adaptive and static load balancing policies in a heterogeneous distributed system model. All the hosts (nodes) an the system are assumed to have the same function but possibly different processing capacities. The overheads and the delays for both job transfer and system state-information exchange are assumed to be nonnegligible. Simulation results show that both adaptive and static policies improve performance dramatically, and that the performance provided by static policies is not much inferior to that provided by adaptive policies. They also show that when overheads are nonnegligibly high at heavy system loads, static policies can provide performance more stable and better than that provided by adaptive policies.<<ETX>>

Flow control and routing algorithms in WAPSN

The performance evaluation of several routing algorithms and the combined effect when four levels of flow control mechanisms are operating simultaneously in a wide area packetswitched network (WAPSN) is made by discrete-event simulation. Both non-adaptive and adaptive routing algorithms are discussed, and then the fixed (non-adaptive routing technique), the shortest-queue (isolated routing technique) and the shortest-path (distributed routing technique) routing algorithms are selected and described for simulation in networks both with and without a multilevel flow control mechanism. The flow control techniques described here are the channel queue limit, the window mechanism and the input buffer limit schemes. We give results for each of the following goals: 1.(a) To evaluate and compare the network performance of the routing algorithms under light, moderate and heavy load conditions during a transient period, subject to changes in the mean arrival rate of messages in networks both with and without a multilevel flow control mechanism. 2.(b) To evaluate and compare the performance of the routing algorithms during the transition of a network protected by an end-to-end flow control mechanism to an unprotected network. 3.(c) To evaluate the effect of varying the update interval for the adaptive routing algorithms. 4.(d) To evaluate and compare the performance of the routing algorithms in response to traffic changes or link failures in a network using a multilevel flow control mechanism. 5.(e) To develop innovative simulation models involving routing algorithms and a multilevel flow control mechanism for packet-switched networks.

A Multimedia Workstation, Yougao

This paper describes the design and the implementation of the Yougao multimedia workstation. Yougao is designed to be object-oriented. It models the virtual work space using objects called “views” and “scenes.” Using views and scenes which manage spaces hierarchically, surrealistic modeling is possible. Yougao has full-color high resolution graphic ability and a hi-fi sound board. High level graphic abilities such as arbitrary degrees of transparency, an abstract color model, and anti-aliasing are supported at the system level. Text is handled with a text manager which has sophisticated formatting abilities. All graphic and text objects can be transformed in various ways. Media representation is completely independent of the device, and all media can be integrated using a media interface description language called R.