With the advent of cheap and powerful hardware for workstations and networks, a new cluster-based architecture for Time Warp simulations has been envisioned. However, fine-grained Time Warp applications that communicate frequently are not the ideal candidates for such architectures due to their high latency communication costs. Hence, designers of fine-grained Time Warp applications on clusters are faced with the problem of reducing the high communication latency of the communication subsystem in such architectures. An efficient communication subsystem consumes a lower fraction of the processing cycles for communication operations and allows the majority of the processing cycles to be used by the application. This increases the performance of Time Warp applications. This thesis reduces the latency of the communication subsystem by selecting one of the following approaches: (i) reducing network latency by employing a higher performance network hardware (i.e., Fast Ethernet versus Myrine...

The Network-Based Problem Solving Environment (NBPSE) paradigm is emerging as an important approach to complex problem solving and advanced computer assisted decision making. The quality of service and the performance that an NBPSE offers to its users is very important. In the case of communication-centered problem solving, i.e., situations where the solution requires frequent exchanges of high volumes of data and information among distributed PSE elements, a determining performance factor can be the communication middleware used to construct the PSE. Examples of such middleware are PVM, MPI, CORBA-compliant object brokers, and specially developed "glue" such as the NC State Lightweight Software Bus (LSB). Many modern scientific NBPSEs use the TCP/IP and/or UDP/IP communication stack. We discuss communication related performance issues through examples drawn from an operational NBPSE (Environmental Decision Support System), some commercial middleware products (SOMobjects, Orbix and ORB...