Performance of the dot product function in radiative transfer code SORD

摘要

The successive orders of scattering radiative transfer (RT) codes frequently call the scalar (dot) product function. In this paper, we study performance of some implementations of the dot product in the RT code SORD using 50 scenarios for light scattering in the atmosphere-surface system. In the dot product function, we use the unrolled loops technique with different unrolling factor. We also considered the intrinsic Fortran functions. We show results for two machines: ifort compiler under Windows, and pgf90 under Linux. Intrinsic (DOT_PRODUCT) function showed best performance for the ifort. For the pgf90, the dot product implemented with unrolling factor 4 was the fastest.