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Performance Management Guide

Optimizing Preprocessors for FORTRAN and C

The KAP and VAST preprocessors for the FORTRAN compiler can restructure FORTRAN source code to better use the POWER family, POWER2, and PowerPC processing unit resources and memory hierarchy. A version of the KAP preprocessor is also available for restructuring the code of C programs. The preprocessors perform memory management optimizations, algebraic transformations, inlining, interprocedural analysis, and other optimizations that improve the performance of FORTRAN or C applications.

Performance tests indicate improvements in the range of 8 to 18 percent, on average, when a suite of programs is compiled with the preprocessors, compared to compiling with the same optimization options for the unpreprocessed version.

The KAP and VAST preprocessors attempt to transform source-level algorithms into algorithms that can take full advantage of the optimizing capabilities of the compiler. The preprocessors also generate listings that identify the transformations performed and areas of your code that prevent transformations from being carried out. The preprocessors analyze source code, and perform transformations that can improve a program's performance.

Any transformation done by the preprocessors can also be accomplished through hand-tuning. The advantages of using a preprocessor rather than hand-tuning are as follows:

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