The ELSI Infrastructure for Scalable Electronic Structure Theory

Kohn-Sham density functional theory is the most widely used workhorse method for first-principles atomistic simulations of materials based on their electronic structure, implemented in a broad range of community codes. A key bottleneck is the construction of the so-called density matrix. For small systems, this is most effectively accomplished by solving a cubic-scaling eigenvalue problem (O(N³) with some measure of the system size, N), while lower-scaling methods for larger systems are typically restricted to specific system classes and/or types of approximate density functionals employed. ELSI is an open-source infrastructure that bridges between different community codes and density matrix construction methods implemented as separate "solver" libraries. The implementation features a simple, flexible interface to multiple solvers, efficient distributed-parallel matrix format conversion, and it supports a broad range of high-performance computing architectures and software stacks.