pShell: The distributed shell parallel programming environment

Communications and the scheduling of tasks are the two most important issues of parallel programming on clusters. Over time, various parallel computing programming models such as remote threads, transparent process migration, message passing, distributed shared memory and optimizing parallel compilers have emerged, assisting the programmer to develop applications which can work seamlessly in such environments. However their acceptance has varied by virtue of the fact that each has introduced new problems with reference to portability, scalability and usability. Sometimes these problems completely violate the underlying notion of such computing. This paper will examine the evolution of cluster computing and identify where deficiencies lie in current programming models, providing a justification for simple languages while providing the reader with an understanding of the Pshell programming environment we are actively developing. Pshell is the 'glue' for producing high-performance parallel applications that can work securely and efficiently in heterogeneous environments. In addition to this, the paper illustrates how such a language can be used to ease the process of writing parallel applications and to overcome some of the limitations inherent in traditional programming models without sacrificing performance.