The design and implementation of portable, efficient, and expressive mechanisms for I/O on complex distributed data structures—such as found in adaptive parallel applications—is a challenging problem that we address in this paper.We describe the design, programmer interface, implementation, and performance of pC++/streams, a library that provides an expressive mechanism for I/O on distributed arrays of variable-sized objects in pC++, an object-parallel language. pC++/streams is intended for developers of parallel programs requiring efficient high-level I/O abstractions for checkpointing, scientific visualization, and debugging.pC++/streams is an implementation of d/streams, a language-independent abstraction for buffered I/O on distributed data structures. We describe the d/streams abstraction and present performance results on the Intel Paragon and SGI Challenge showing that d/streams can be implemented efficiently and portably.

Existing tools for locating performance bottlenecks of message passing parallel programs either provide visualizations or profiles of program executions only; they do not highlight the cause of poor program performance. From the perspective of the application, the location and cause of performance problems in terms of procedures, processors and data structures are all important. Identifying the cause of poor performance necessitates the need to expose how well the underlying algorithm has been mapped onto the parallel machine.