Parallelization of a quantum scattering code using P-grade: A case study

We used P-GRADE, a graphical tool and programming environment to parallelize atomic level reaction dynamics codes, In the present case study ABC, a quantum reactive scattering code written in FORTRAN has been parallelized. We used the possibly coarsest grain parallelization, i.e. a complete calculation at each total energy is performed on a node. From the automatic schemes offered by P-GRADE, the task farm was selected. The FORTRAN code was separated into an input/output and a working section. The former, enhanced by a data transfer section operates on the master, the latter on the slaves. Small sections for data transfer were written in C language, The P-GRADE environment offers a user-friendly way of monitoring the efficiency of the parallelization. On a 20-processor NPACI Rocks cluster the speed-up is 99 percent proportional to the number of processors. P-GRADE proved to be user-friendly and made the programmer's work very efficient.