Besides these hardware overheads, there are certain software overheads imposed by libraries, parallel compilers, tools and operating systems.
The parallel programming languages are developed for parallel computer environments. These are developed either by introducing new languages (e.g. occam) or by modifying existing languages like, (C and FORTRAN). Normally the language extension approach is preferred by most computer designs. This decreases compatibility problem. High-level parallel constructs were added to C and FORTRAN to make these languages suitable for parallel computers. Besides these, optimizing compilers are designed to automatically detect the parallelism in program code and change the code to parallel code.
In addition to development of compilers and languages for parallel programming, a parallel programming environment should also have supporting tools for text editing and development of parallel programmes.
Let us now talk about the examples of parallel programming environments of Cray Y-MP software and Intel paragaon XP/S.
The Cray Y-MP system works with UNICOS operating system. It has two FORTRAN compilers CFT and CFT 77 for automatic vector code generation. The system software has large library of routines, program management utilities, assembler UNICOS and debugging aids written in C. It supports optimizing, vectorizing, concurrentising facilities for FORTRAN compilers and also has vetorizing and optimizing C compiler. The Cray Y-MP has three multitasking / multiprocessing methods namely, (i) microtasking (ii) macrotasking, , (iii) autotasking. As well, it has a subroutine library, containing a variety of utilities, high performance subroutines along with scientific routines and math.
The Intel Paragaon XP/S system is an extension of Delta systems and Intel iPSC/860, and is a mesh and scalable connected multicompiler which is executed in a distributed memory system.
The processors that for nodes of the system are 50 MHz i860 XP Processors. Furthermore, it uses distributed UNIX based OS technology. The languages supported by Paragaon have C, C++, ADA and Data Parallel Fortran. The tools for integration contain FORGE and Cast parallelisation tools. The programming environment contains an Interactive Parallel Debugger (IPD).