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.

The RT code SORD together with the interface that runs all the mentioned tests are publicly available from ftp://maiac.gsfc.nasa.gov/pub/skorkin/SORD_IP_16B (current release) or by email request from the corresponding (first) author.

Date Published: 24 October 2016
PDF: 7 pages
Proc. SPIE 10007, High-Performance Computing in Geoscience and Remote Sensing VI, 1000705 (24 October 2016); doi: 10.1117/12.2240592

Published in SPIE Proceedings Vol. 10007:
High-Performance Computing in Geoscience and Remote Sensing VI
Bormin Huang; Sebastián López; Zhensen Wu; Jose M. Nascimento; Jun Li; Valeriy V. Strotov, Editor(s)