Roberto Di Remigio has successfully secured a preparatory access PRACE allocation on the newly installed JUWELS Booster system for ENCCS work on VeloxChem. JUWELS Booster is an upgrade module to the JUWELS Cluster supercomputer and is the fastest supercomputer in Europe. This allocation will be used to investigate an alternative algorithm for the computation of electron repulsion integrals.
A “late contraction” strategy will be implemented: computation of the integrals will be performed in the primitive basis, using the already optimized CPU algorithm. The integrals will be contracted to build the Fock matrix, a two-index quantity, which is finally transformed to the smaller contracted basis with a sparse matrix-matrix multiplication performed on the accelerator device. This algorithm minimizes memory bandwidth issues between host and device, while fully leveraging the efficiency of native matrix-matrix multiplication libraries on GPU accelerators.