Using Pthreads in Fortran

This article describes the way to use pthreads library in Fortran programs. With most of the modern day processors having more and more built in capability of parallelism, there is ample need of utilizing this power at the application level, especially in scientific applications which involves lots of number crunching and multi GB disk handling. To utilize the power of multi threading for scientific applications, where FORTRAN still seems to be the de-facto choice, many compiler vendors like Intel have started supporting Open MP based parallelism. Though Open MP is a very good way of introducing parallelism in existing sequential FORTRAN programs, it only provides you with a mostly declarative style of programming where all the parallelization is handled at the compiler level. If you need to have explicit programming control by writing code (like handling disk based quantum chemical calculations, where explicit buffering is extremely useful), there is a need to use threading libraries like the pthread library. I will stick to using pthread in this article, but similar techniques can be used with any other threading library. I have also made the choice of using pthreads because it is widely available and recognized by POSIX standards. For detailed discussion on pthreads and programming with it refer the book from O'Reilly.