Application of Fortran Pthreads to Linear Algebra and Scientific Computing

Pthreads is a POSIX standard library for expressing concurrency on uniprocessor and symmetric multiprocessor computers. Typical multithreaded applications include database manipulation, operating systems, or any algorithm displaying task-level concurrency. These types of programs are generally coded in C. Hence, the POSIX standard only defines a C interface to Pthreads. The lack of a standard Fortran interface has limited the use of Pthreads for scientific and numerically intensive applications. However, many of these applications would benefit from multithreading. For example, the manipulation and solution of dense linear systems with 10,000 to 40,000 simultaneous equations are made up of many independent tasks that may be executed concurrently. The effectiveness of Fortran and Pthreads for scientific programming will be demonstrated using two linear algebra routines (matrix multiplication and Gaussian elimination) and two algorithms from the Command, Control, Communication, and Intelligence Benchmark. This work builds on the Fortran interface to Pthreads presented at the 40th Cray Users Group Conference.