Tier 2 Code Development Project

Numerical Methods/Algorithms

GAMESS is a well-known quantum chemistry code, which relies on several different algorithms depending on the level of theory. A key code is the second order Møller-Plesset (MP2) algorithm that relies on integral transformations, matrix and vector multiplies, and Gaussian basis sets with an iterative solver. In addition, the parallel coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) method in conjunction with highly accurate augmented basis sets will be enabled by the large node memory of Theta. The Fragment Molecular Orbital (FMO) method uses electronic structure theory, so an FMO-MP2 calculation requires the same mathematics and computational considerations as in a normal MP2 calculation.

Parallelization

The parallel programming system is the distributed data interface (DDI) that provides global addressable memory and one-sided communications. A recent improvement, GDDI/3 (Three Level GDDI), added a higher level of coarse-grained parallelism that runs multiple concurrent instances of the FMO method. OpenMP threading has been recently introduced, with promising thread scaling. The project will include vectorization of integral code.

Application Development

• Threading and vectorization of the expensive electron repulsion integrals (ERIs)
  • Existing strategies for vectorization of the Rys Polynomial ERI code will be tested on Intel hardware
  • Threading the main SCF driver and MP2 code
• Optimize underlying dynamics code used for FMO method
  • Optimize periodic boundary condition code in underlying dynamics
  • Test multiple time-stepping algorithms
  • Integrate replica exchange MD with the new GDDI/3 parallelization scheme

Portability

Focus will be on porting to Theta.