There has been considerable interest in delivering information to distributed mobile clients via wireless broadcast. Information transmitted periodically over wireless media can be regarded as a virtual disk, which we call an airdisk, analogous to a standard magnetic disk. Airdisks offer an efficient mechanism for delivering personalized information services to mobile clients with portable or laptop computers by broadcasting data and allowing clients to filter out the items of interest to them. We study the problem of scheduling the order in which data items are broadcast so as to minimize the access time of the clients, focusing on the case where the server inserts an index at the start of the broadcast period. We observe that the problem is analogous to that of determining how data should be laid out on the disk, and show that the problem is in general NP-complete. We develop a branch-and-bound procedure for solving the problem optimally, and then develop a fast, simple heuristic. The results of our simulation experiments show that the heuristic runs substantially faster than the branch-and-bound procedure, and yet produces schedules that are only slightly longer.

No abstract available.

The I/O bottleneck in parallel computer systems has recently begun receiving increasing interest. Most attention has focused on improving the performance of I/O devices using fairly low level parallelism in techniques such as disk striping and interleaving. Widely applicable solutions, however, will require an integrated approach which addresses the problem at multiple system levels, including applications, systems software, and architecture. We propose that within the context of such an integrated approach, scheduling parallel I/O operations will become increasingly attractive and can potentially provide substantial performance benefits. We describe a simple I/O scheduling problem and present approximate algorithms for its solution. The costs of using these algorithms in terms of execution time, and the benefits in terms of reduced time to complete a batch of I/O operations, are compared with the situations in which no scheduling is used, and in which an optimal scheduling algorithm is used. The comparison is performed both theoretically and experimentally. We have found that, in exchange for a small execution time overhead, the approximate scheduling algorithms can provide substantial improvements in I/O completion times.

No abstract available.

Events are occurence instance of actions. The thesis of this paper is that the use of "actions", instead of events, greatly simplifies the problem of concurrent debugging.

Reports on the initial experimental evaluation of ROPE (reusability-oriented parallel programming environment), a software component reuse system. ROPE helps the designer find and understand components by using a new classification method called structured relational classification. ROPE is part of a development environment for parallel programs which uses a declarative/hierarchical graphical programming interface. This interface allows use of components with different levels of abstraction, ranging from design units to actual code modules. ROPE supports reuse of all the component types defined in the development environment. Programs developed with the aid of ROPE were found to have error rates far less than those developed without ROPE.>

No abstract available.