MPI/OpenMP Hybrid Parallel Algorithm for Hartree−Fock Calculations

A new message passing interface/open multiprocessing (MPI/OpenMP) hybrid parallel algorithm of the Hartree−Fock calculation is developed and implemented into the quantum chemistry program package GAMESS. In the algorithm, internode distribution is performed by MPI and intranode parallelization by OpenMP. It is applied to a TiO2 cluster (Ti35O70, 6-31G, 1635 basis functions) and to insulin (C257H381N65O77S6 2−, STO-3G, 2430 basis functions) using the Cray XT5 supercomputer (quad-core Opteron 2.3 GHz, 2048 CPU cores). The speed-ups of the whole calculations, including the initial guess generation, are 1238 and 745 using 2048 CPU cores for the TiO2 cluster and insulin, respectively. Hartree−Fock calculations with hundreds or thousands of CPU cores are now practical.