An Optimization Experiment with the Community Land Model on the Cray X1

Abstract

Version 2.1 of the Community Land Model (CLM) uses data and control structures that challenge the capabilities of the Cray Fortran compiler. We describe an optimization experiment where we modified the CLM data structure within a computationally expensive tree of subroutines and compared performance with the original code. The modifications produce a 20% increase in performance on an IBM p690 and 5.86 to 7.29 times this performance on a Cray X1. The modified code may also be as maintainable andextensible as the original code.