关键词: 第一性原理计算, 密度泛函理论, 格林函数, MPI, 并行计算

Abstract: To solve long time-consuming problem in analysis of large-scale quantum transport systems based on first-principles calculations, we analyze hot spots of self-consistent iterations within the framework that combines non-equilibrium Green's function with density functional theory, namely DFT+NEGF method. Two parallel computing schemes based on MPI/OpenMP are proposed to deal with energy point integration and matrix inversion/multiplication. For energy point integral parallelism, sparse matrix as well as energy points should be assigned to each process over data initialization according to round-robin scheduling algorithm. Either MPI based ScaLAPACK subroutine or OpenMP based Intel MKL subroutine can be called to realize matrix inversion/multiplication parallelization. A sub-linear speedup ratio curve is obtained for energy point integral parallelism due to the fact that calculations related with different energy points are mutually independent. OpenMP parallelism adopts shared memory patterned data exchange mechanism and overhead of switching threads is rather small, and consequently it is better in computing efficiency but worse in code scalability than MPI implementation.

Key words: first-principles calculations, density functional theory, Green's function, MPI, parallel computing