Scalability analysis of Dalton, a molecular structure program

• We performed a detailed performance analysis of Dalton a computational chemistry code.
• We improved the performance of numerical and communication operations.
• We reorganized the master–worker architecture with teams of workers to increase the scalability.
• Optimizations allow to use efficiently a significant larger number of nodes than before.

Dalton is a molecular electronic structure program featuring common methods of computational chemistry that are based on pure quantum mechanics (QM) as well as hybrid quantum mechanics/molecular mechanics (QM/MM). It is specialized and has a leading position in calculation of molecular properties with a large world-wide user community (over 2000 licenses issued). In this paper, we present a performance characterization and optimization of Dalton. We also propose a solution to avoid the master/worker design of Dalton to become a performance bottleneck for larger process numbers. With these improvements we obtain speedups of 4x, increasing the parallel efficiency of the code and being able to run in it in a much bigger number of cores.