Author(s)

S. Stephany, R. V. Correa, C. L. Mendes and A. J. Preto

Abstract

Identifying performance bottlenecks in a radiative transfer application S. Stephanyi, R. V. Correa", C. L. Mendes* & A. J. Preto* 'Applied Computing Lab (LAC) ^Baloon Facility (SLB), Brazilian Institute for Space Research (INPE), Abstract The Hydrolight software is a well known radiative transfer solver, written in Fortran 77, intended for hydrologic optics problems. It was developed by C. D. Mobley and it is based on an invariant imbedding methodology that yields a system of non-linear ordinary differential equations, the Riccati equations, which are solved by routines that implement numerical methods. This work proposes an innovative strategy for identifying performance bottlenecks and optimising a code using both standard profiling tools and accessing specific cpu registers and a time counter. The execution profile in a RISC worst at ion shows that most of the processing time is spent in solv- ing Riccati equations, what is accomplished by a Runge-Kutta algorithm. The time-

Keywords