9.1.2 Other Performance Strategies

Assuming that you have experimented with using a variety of optimization options, compiling your program and measuring actual runtime performance, the next step might be to look closely at the Fortran source program to see what further tuning can be tried.

Focusing on just those parts of the program that use most of the compute time, you might consider the following strategies:

• Replace handwritten procedures with calls to equivalent optimized libraries.

• Remove I/O, calls, and unnecessary conditional operations from key loops.

• Eliminate aliasing that might inhibit optimization.

• Rationalize tangled, spaghetti-like code to use block IF.

These are some of the good programming practices that tend to lead to better performance. It is possible to go further, hand-tuning the source code for a specific hardware configuration. However, these attempts might only further obscure the code and make it even more difficult for the compiler’s optimizer to achieve significant performance improvements. Excessive hand-tuning of the source code can hide the original intent of the procedure and could have a significantly detrimental effect on performance for different architectures.