Zipcode is a message-passing and process-management system that was designed for multicomputers and homogeneous networks of computers in order to support libraries and large-scale multicomputer software. The system has evolved significantly over the last five years, based on our experiences and identified needs. Features of Zipcode that were originally unique to it, were its simultaneous support of static process groups, communication contexts, and virtual topologies, forming the "mailer" data structure. Point-to-point and collective operations reference the underlying group, and use contexts to avoid mixing up messages. Recently, we have added "gather-send" and "receive-scatter" semantics, based on persistent Zipcode "invoices," both as a means to simplify message passing, and as a means to reveal more potential runtime optimizations. Key features in Zipcode appear in the forthcoming MPI standard. Keywords: Static Process Groups, Contexts, Virtual Topologies, Point-to-Point Communica...

Tools for parallel systems today range from specification over debugging to performance analysis and more. Typically, they help the programmers of parallel algorithms from the early development stages to a certain level of program optimization. However, in HPC (High Performance Computing) today the end-user of massively parallel CFD (Computational Fluid Dynamics)-programs has little or no support in his work. The scientific engineer who often runs his application on a parallel computer somewhere in the WAN (Wide Area Network) and visualizes the enormous amounts of simulation data on a graphical workstation in his LAN (Local Area Network) has needs which are by far not covered by state of the art visualization systems. The tool proposed here follows a strategy which differs completely from existing, batch-oriented, and strictly sequential methods of the working process in the application cycle of parallel HPC applications. It allows both on-line visualization and interactive program steering of massively parallel CFD-applications. The parameters of the mathematical model and the numerical methods build objects of a database which can be accessed by an object-oriented graphical user interface via visualization and modification operators. Experiences with this new tool concept VIPER (VIsualization of Parallel numerical simulation algorithms for Extended Research) applied on a real-world and industrial scientific application will be shown. 1.

As clusters of workstation get more and more popular (and as a consequence bigger and bigger), disks of these nodes are only used for the system and temporary files. Systems that offer an abstraction of the storage devices in a distributed manner for a cluster are few and far between. In this paper we introduce an extension to the implementation of NFS more suited to the context of clusters because it makes use of the disk space available on the nodes of the cluster instead of the one available on the server only. Our solution relies on the same principles as PVFS: a metaserver and I/O daemons. We present its architecture, the first implementation we did and early performance results. 1