Some issues in the relationship of coding style and compiler optimization are discussed with regard to Fortran 90 array notation. A review of several important Fortran 90 array constructs and their performance on vector and scalar hardware sets the stage for a more detailed example based on the kernel of a finite difference computational fluid dynamics model, specifically the nonlinear shallow water equations. Special attention is paid to the optimization of memory use and memory traffic. It is

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... shown that the style of coding interacts with the rules of Fortran 90 and the current state of the art of Fortran 90 compilers to produce a fairly wide range of performance levels. Although performance degradations are typically small, a few cases of more serious loss of effciency are identified and discussed.