Thanks to MPI, writing portable message passing parallel programs is almost a reality. One of the remaining problems is file I/O. Although parallel file systems support similar interfaces, the lack of a standard makes developing a truly portable program impossible. It is not feasible to develop large scientific applications from scratch for each generation of parallel machine, and, in the scientific world, a program is not considered truly portable unless it not only compiles, but also runs efficiently. The MPI-IO interface is being proposed as an extension to the MPI standard to fill this need. MPI-IO supports a high-level interface to describe the partitioning of file data among processes, a collective interface describing complete transfers of global data structures between process memories and files, asynchronous I/O operations, allowing computation to be overlapped with I/O, and optimization of physical file layout on storage devices (disks).

We present several elegant methods used in GraphPack, an educational package, for three dimensional embedding of graphs, as well as a two dimensional layout method, namely barycentric embedding. After that, a program for automatic recognition of graphs is introduced. In addition, we show how graphs in GraphPack format can be exported into XXg format. Finally, we describe the client/server capabilities of GraphPack designed for providing communication with other tools and application programs written in C and C++.

Parallel computer architectures require innovative software solutions to utilize their capabilities. This statement is true for system software no less than for application programs. File system development for the IBM SP product line of computers started with the Vesta research project, which introduced the ideas of parallel access to partitioned files. This technology was then integrated with a conventional Advanced Interactive Executive™ (AIX™) environment to create the IBM AIX Parallel I/O File System product. We describe the design and implementation of Vesta, including user interfaces and enhancements to the control environment needed to run the system. Changes to the basic design that were made as part of the AIX Parallel I/O File System are identified and justified.

Applications on MPPs often require a high aggregate bandwidth of low-latency I/O to secondary storage. This requirement can met by internal parallel I/O subsystems that comprise dedicated I/O nodes, each with processor, memory, and disks.Massively parallel processors (MPPs), encompassing from tens to thousands of processors, are emerging as a major architecture for high-performance computers. Most major computer vendors offer computers with some degree of parallelism, and many smaller vendors specialize in producing MPPs. These machines are targeted for both grand-challenge problems and general-purpose computing.Like any computer, MPP architectural design must balance computation, memory bandwidth and capacity, communication capabilities, and I/O. In the past, most design research focused on the basic compute and communications hardware and software. This led to unbalanced computers that had relatively poor I/O performance. Recently, researchers have focused on designing hardware and software for I/O subsystems in MPPs. Consequently, most current MPPs have an architecture based on an internal parallel I/O subsystem (the "Architectures with parallel I/O" sidebar describes some examples). In these computers, this subsystem encompasses a collection of I/O nodes, each managing and providing I/O access to a set of disks. The I/O nodes connect to other nodes in the system by the same switching network that connects the compute nodes.In this article we'll examine why many MPPs use parallel I/O subsystems, what architecture is best for such a subsystem, and how to implement the subsystem. We'll also discuss how parallel file systems and their user interfaces can exploit the parallel I/O to provide enhanced services to applications.The systems discussed in this article are mostly tightly coupled distributed-memory MIMD (multiple-instruction, multiple-data) MPPs. In some cases, we also discuss shared-memory and SIMD (single-instruction, multiple-data) machines. We'll discuss three node types. Compute nodes are optimized to perform floating-point and numeric calculations, and have no local disk except perhaps for paging, booting, and operating-system software. I/O nodes contain the system's secondary storage, and provide the parallel file-system services. Gateway nodes provide connectivity to external data servers and mass-storage systems. In some cases, individual nodes can serve as more than one type. For example, the same nodes often handle I/O and gateway functions. The "Terminology" sidebar defines some other terms used in this article.

In this paper, we describe diierent methods for three dimensional embedding of graphs, as well as a two dimensional layout method, namely barycentric embedding. In addition, we present a program for automatic recognition of graphs. We nally describe servers for graph drawing routines that can be called from C or C++ programs and applications such as Mosaic.