HP 3000 Manuals HP 3000 Manuals
Chapter 4 Optimizing HP C Programs This chapter discusses the following: * When and how to use the optimizer. * The four levels of optimization. * Profile-based optimization. The HP C optimizer transforms programs so machine resources are used more efficiently. The optimizer can dramatically improve application run-time speed. HP C performs only minimal optimizations unless you specify otherwise. You activate additional optimizations using HP C command line options. There are four major levels of optimization: levels 1, 2, 3, and 4. Level 4 optimization can produce the fastest executable code. Level 4 is a superset of the other levels. Additional parameters enable you to control the size of the executable program, compile time, and aggressiveness of the optimizations performed. Compile time memory and CPU usage increase with each higher level of optimization due to the increasingly complex analysis that must be performed. You can control the trade-offs between compile-time penalties and code performance by choosing the level of optimization you desire. Generally, the optimizer is not used during code development. It is used when compiling production-level code for benchmarking and general use.