1.1 Introduction

Parallel programming requires interaction between the various processes that are simultaneously run on the individual processors and this is enabled by passing messages between the various processors. This important class of parallel machines, called Message-passing architectures, employs complete computers as building blocks including the microprocessor memory and the I/O system and provides communication between processors as explicit I/O operations. This style of architecture has much in common with the network of workstations, or clusters, except that the packaging of nodes is typically much tighter and the network is of much higher capability than a standard local area network.