This paper describes current activities of the MPI-2 Forum. The MPI-2 Forum is a group of parallel computer vendors, library writers, and application specialists working together to define a set of extensions to MPI (Message Passing Interface). MPI was defined by the same process and now has many implementations, both vendor-proprietary and publicly available, for a wide variety of parallel computing environments. In this paper we present the salient aspects of the evolving MPI-2 document as it now stands. We discuss proposed extensions and enhancements to MPI in the areas of dynamic process management, one-sided operations, collective operations, new language binding, real-time computing, external interfaces, and miscellaneous topics. 1 Introduction During 1993 and 1994, a group of parallel computer vendors, library writers, and application scientists met regularly to define a standard interface for message-passing libraries. The result of this effort was MPI (Message-Passing Interfa...

Lightweight threads are becoming increasingly useful in supporting parallelism and asynchronous control structures in applications and language implementations. Recently, systems have been designed and implemented to support interprocessor communication between lightweight threads so that threads can be exploited in a distributed memory system. Their use, in this setting, has been largely restricted to supporting latency hiding techniques and functional parallelism within a single application. However, to execute data parallel codes independent of other threads in the system, collective operations and relative indexing among threads are required. This paper describes the design of ropes: a scoping mechanism for collective operations and relative indexing among threads. We present the design of ropes in the context of the Chant system, and provide performance results evaluating our initial design decisions. Research supported by the National Aeronautics and Space Administration under NASA Contract No. NASA-

Threads provide a useful programming model for asynchronous behavior because of their ability to encapsulate units of work that can then be scheduled for execution at runtime, based on the dynamic state of a system. Recently, the threaded model has been applied to the domain of data parallel scientific codes, and initial reports indicate that the threaded model can produce performance gains over non-threaded approaches, primarily through the use of overlapping useful computation with communication latency. However, overlapping computation with communication is possible without the benefit of threads if the communication system supports asynchronous primitives, and this comparison has not been made in previous papers. This paper provides a critical look at the utility of lightweight threads as applied to data parallel scientific programming.

DECK (Distributed Executive Communication Kernel) is a communication layer that provides support for multithreading and fault tolerance. The approach retained in DECK is close to other distributed communication kernels like PM2, Athapascan, Nexus, TPVM or Chant in its way to integrate communication and multithreading to efficiently overlap communication by computation and provide low latency mechanisms to remote thread creation. However, DECK differs from these communication kernels from the services offered and its modular architecture. The main goal of DECK is to implement a new model for the design of distributed executive kernel to efficiently use the new underlying hardware architectures (SMP architectures and fast communication adapters like Myrinet or memory oriented adapter like SCI) and provide a portable layer that abstract the problems linked with the integration of communication and multithreading while offering support for heterogeneity. A great lack in the cur...