makes the problem much harder. In order to build costeffective NOW systems which can deliver MPP-like performance, several important problems need to be solved. Examples of such problems include designing efficient messaging layers; network interface design for low-latency and high-throughput communication; architectural and operating systems support for fast communication and synchronization; collective communication support; distributed memory implementation with PVM and MPI; memory models and architectural supports for implementing distributed shared memory paradigm; programming environments; load balancing; scheduling; fault tolerance; run time support; and performance evaluation.
In this special issue we have attempted to include some of the state-of-the-art research results, which lead the parallel processing community towards the realization of the NOW paradigm. We received 53 manuscripts in response to our call for papers. Due to many high quality submissions, we had to go through an extremely difficult selection process. We are spreading out the selected papers over two issues. This first issue, with the theme of hardware and software, contains eight regular papers and two research notes. A set of additional papers, emphasizing performance evaluation, scheduling, and fault-tolerance, is tentatively scheduled for the June 1997 issue. A brief summary of the papers appearing in this issue is as follows:
M. Lauria and A. Chien provide a new design approach for low level communication layers by providing a closer integration with the upper layer. They describe their design with respect to MPI-FM, a high performance implementation of MPI on networks of workstations connected by a Myrinet network.
J. Bruck et al. present an efficient design and implementation of the collective communication part in MPI that is optimized for clusters of workstations. They have implemented their system on a collection of IBM RS/6000 workstations connected via a 10MBit Ethernet LAN.
I. Foster et al. propose techniques that allow multiple