9.1 Programming Languages

While there are hundreds of programming languages available, when it comes to writing code for high-performance clusters, there are only a couple of realistic choices. For pragmatic reasons, your choices are basically FORTRAN or C/C++.

Like it or not, FORTRAN has always been the lingua franca of high-performance computing. Because of the installed base of software, this isn't likely to change soon. This doesn't mean that you need to use FORTRAN for new projects, but if you have an existing project using FORTRAN, then you'll need to support it. This comes down to knowing how your cluster will be used and knowing your users' needs.

FORTRAN has changed considerably over the years, so the term can mean different things to different people. While there are more recent versions of FORTRAN, your choice will likely be between FORTRAN 77 and FORTRAN 90. For a variety of reasons, FORTRAN 77 is likely to get the nod over FORTRAN 90 despite the greater functionality of FORTRAN 90. First, the GNU implementation of FORTRAN 77 is likely to already be on your machine. If it isn't, it is freely available and easily obtainable. If you really want FORTRAN 90, don't forget to budget for it. But you should also realize that you may face compatibility issues. When selecting parallel programming libraries to use with your compiler, your choices will be more limited with FORTRAN 90.

C and C++ are the obvious alternatives to FORTRAN. For new applications that don't depend on compatibility with legacy FORTRAN applications, C is probably the best choice. In general, you have greater compatibility with libraries. And at this point in time, you are likely to find more programmers trained in C than FORTRAN. So when you need help, you are more likely to find a helpful C than FORTRAN programmer. For this and other reasons, the examples in this book will stick to C.

With most other languages you are out of luck. With very few exceptions, the parallel programming libraries simply don't have binding for other languages. This is changing. While bindings for Python and Java are being developed, it is probably best to think of these as works in progress. If you want to play it safe, you'll stick to C or FORTRAN.