DiStasio Research Group


Fig. 1: Strong scaling plots for hybrid density functional theory based ab initio molecular dynamics simulations of the α-glycine molecular crystal using the linear-scaling exact exchange (Exx) algorithm in Quantum ESPRESSO. Unit cells containing 16 (160 atoms, 240 bands), 32 (320 atoms, 480 bands), and 64 (640 atoms, 960 bands) glycine molecules as a function of z, the number of MPI ranks/band, were considered in this plot. On Mira, 30,720 cores (1920 MPI ranks x 16 cores/rank) were utilized for the largest system considered here (gly064, z=2.0), retaining over 88% of the ideal efficiency (dashed lines).

Fig. 2: Weak scaling plots for hybrid density functional theory based ab initio molecular dynamics simulations of the α-glycine molecular crystal using the linear-scaling exact exchange (Exx) algorithm in Quantum ESPRESSO. On Mira, 30,720 cores (1920 MPI ranks x 16 cores/rank) were utilized for the largest system considered here (gly064, z=2.0), retaining over 80% of the ideal efficiency (dashed lines). Deviations from ideal scaling are primarily due to the use of the fast Fourier transform (which scales non-linearly) to provide the maximally localized Wannier functions in real space.



Fig. 3: Threading efficiency plots for hybrid density functional theory based ab initio molecular dynamics simulations of the α-glycine molecular crystal using the linear-scaling exact exchange (Exx) algorithm in Quantum ESPRESSO. On Mira, the use of 16 cores/rank retained over 84% (85 Ry basis) and 92% (150 Ry basis) of the ideal efficiency (dashed line) for a unit cell containing 64 glycine molecules.