10.6 Closing notes

In this chapter, we have covered some of the efforts in the area of languages that have been developed to allow programs to be written for scalable computing. There is a tension between pure FORTRAN-77, FORTRAN 90, HPF, and message passing as to which will be the ultimate tools for scalable, high performance computing.

Certainly, there have been examples of great successes for both FORTRAN 90 (Thinking Machines CM-5) and HPF (IBM SP and others) as languages that can make excellent use of scalable computing systems. One of the problems of a high-level language approach is that sometimes using an abstract high-level language actually reduces effective portability.

The languages are designed to be portable, but if the vendor of your particular scalable computer doesn't support the language variant in which you have chosen to write your application, then it isn't portable. Even if the vendor has your language available, it may not be tuned to generate the best code for their architecture.

One solution is to purchase your compilers from a third-party company such as Pacific Sierra or Kuck and Associates. These vendors sell one compiler that runs across a wide range of systems. For users who can afford these options, these compilers afford a higher level of portability.

One of the fundamental issues is the chicken-and-egg problem. If users don't use a language, vendors won't improve the language. If all the influential users (with all the money) use message passing, then the existence of an excellent HPF compiler is of no real value to those users.

The good news is that both FORTRAN 90 and HPF provide one road map to portable scalable computing that doesn't require explicit message passing. The only question is which road we users will choose.