Improving the Scalability of the Overlapping Fragments Method Code

The overlapping methods code for electronic structure calculations of large organic systems was benchmarked and profiled. Based on the profiling results, several performance and scalability bottlenecks caused by communication were identified. The code was then refactored to improve its performance with respect to these identified weak points. The modified code extends the maximal system size where good scaling is observed on Curie machine from 4,000 atoms to 16,000 atoms. On the other hand, we found that on Hermit machine the original code already exhibits rather good scaling and consequently the modified code leads to minor improvements only.