README.md

# PFARM in the United European Applications Benchmark Suite (UEABS)
## Document Author: Andrew Sunderland (andrew.sunderland@stfc.ac.uk) , STFC, UK.


## Introduction
PFARM is part of a suite of programs based on the ‘R-matrix’ ab-initio approach to the vari-tional solution of the many-electron Schrödinger equation for electron-atom and electron-ion scattering. The package has been used to calculate electron collision data for astrophysical applications (such as: the interstellar medium, planetary atmospheres) with, for example, var-ious ions of Fe and Ni and neutral O, plus other applications such as data for plasma model-ling and fusion reactor impurities. The code has recently been adapted to form a compatible interface with the UKRmol suite of codes for electron (positron) molecule collisions thus ena-bling large-scale parallel ‘outer-region’ calculations for molecular systems as well as atomic systems. 
In this README we give information relevant for its use in the UEABS.

### Standard CPU version
The PFARM outer-region application code EXDIG is domi-nated by the assembly of sector Hamiltonian matrices and their subsequent eigensolutions. The code is written in Fortran 2003 (or Fortran 2003-compliant Fortran 95), is parallelised using MPI and OpenMP and is designed to take advantage of highly optimised, numerical library routines. Hybrid MPI / OpenMP parallelisation has also been introduced into the code via shared memory enabled numerical library kernels. 

### GPU version
Accelerator-based implementations have been implemented for EXDIG, using off-loading (MKL or CuBLAS/CuSolver) for the standard (dense) eigensolver calculations that dominate overall run-time.