Two-Electron Integral Evaluation
The two-electron integrals, also known as electron repulsion integrals, are ubiquitous in quantum chemistry, appearing in the Hartree-Fock method and any correlated method based upon it as well as in density functional methods. The two-electron integral computation is a time-consuming step, and an efficient integral program is an important part of a quantum chemistry code. When designing parallel algorithms for computation of the two-electron integrals, assuming that an efficient scalar code exists, issues of particular importance are load balancing of the nonuniform computational tasks involved as well as utilization of the permutational symmetry of the integrals. In this chapter we will first discuss a few basic issues pertaining to the computation of the two-electron integrals, and we will then examine different parallel implementations of the integral computation, using either a simple static load balancing scheme or employing a manager-worker model for dynamically distributing the work.