/optimize qualifier sets the base optimization and
code analysis level, ranging from 0 (no optimization) to 5 (maximum
optimization). The optimization level can also be modified on a
loop-by-loop basis by the
C*$* optimize (<integer>)
directive. Some of the code analysis techniques can be enabled with
The meaning of each of the different optimization levels is as
follows. Each optimization level is cumulative, for example, level 4
performs what is listed below for that level, in addition to what is
listed for levels 0-3.
- 0 - KAP performs no loop optimization.
- 1 - KAP performs only simple analysis and optimization.
Induction variables are recognized. DO loop interchanging
techniques are applied.
- 2 - Lifetime analysis is performed to determine when
last-value assignment of subprogram-local scalar variables is
necessary. More powerful data dependence tests are used.
- 3 - More loop interchanging is attempted, such as
interchanging of triangular loops. Special-case data dependence
tests are used. Special index sets called wraparound variables
- 4 - Loop interchanging around reductions is attempted.
More exact data dependence tests are used.
- 5 - Array expansion is enabled at this point.
A higher optimization level results in more optimization, more
analysis, and more ambitious transformations, along with increased
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