The essential idea of the GLST algorithm is to keep relevant algebraic expressions for long-range electrostatic interactions within a target accuracy, to reduce the number of cubature nodes and also avoid having cubature nodes that make negligible contribution to the calculation. This includes the truncation of the integral in Eq. 7 and the GLST cubature (Eq. 12), which form the basis for handling PBC via wraparound and box repeats. In this formulation, most of the calculations can be done separately for individual atoms and cells. And interactions between an atom and a cell is a dot product between the Q-factor for the atom and the structure factor of the cell weighed by the energy and force prefactors (cf., Eqs. 19 and 20). By keeping arrays that match indices of other cells relative to the current cell in their roles for different αgroups, wrap-arounds, and box repeats, parallelization can be achieved in those operations as well, the end result being an O(N) scaling .