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Keywords: performance evaluation, TAU, PRM, Fortran 2008, Co-array Fortran
This paper summarizes a strategy for parallelizing a legacy Fortran 77 program using the object-oriented (OO) and coar- ray features that entered Fortran in the 2003 and 2008 stan- dards, respectively. OO programming (OOP) facilitates the construction of an extensible suite of model-verification and performance tests that drive the development. Coarray par- allel programming facilitates a rapid evolution from a serial application to a parallel application capable of running on multi-core processors and many-core accelerators in shared and distributed memory. We delineate 17 code moderniza- tion steps used to refactor and parallize the program, and study the resulting performance. Our scaling studies show that the bottleneck in the performance was due to the im- plementation of the collective sum procedure. Replacing the sequential procedure with a binary tree procedure improved the scaling performance of the program. This bottleneck will be resolved in the future by new collective procedures in Fortran 2015.
Created: Mon Dec 3 16:37:16 2001
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