4.1.4 /roundoff, /r, (/roundoff=3)

The /roundoff qualifier allows you to specify the change from serial roundoff error that is tolerable. If an arithmetic reduction is accumulated in a different order than in the scalar program, the roundoff error is accumulated differently and the final result may differ from that of the original program. While the difference is usually insignificant, certain restructuring transformations performed by KAP must be disabled to obtain exactly the same results as the scalar program.

KAP classifies its transformations by the amount of difference in roundoff error that can accumulate so you can decide what level of roundoff error differences is allowable. The /roundoff command qualifier has the values 0 to 3.

Roundoff levels are cumulative, performing what is listed for each level, as well as what is listed for the lower levels. The meaning of each roundoff level is as follows:

• 0 - Allow no roundoff-changing transformations.

• 1 - Enable expression simplification and code floating. Recognize arithmetic reductions. Allow loop interchanging around arithmetic reductions, if /optimize >4. Allow loop rerolling, when /scalaropt >1.

• 2 - Allow reciprocal substitution in loops.

• 3 - Recognize induction variables whose types are not the default integer type if /scalaropt >2 or /optimize >1. Enable memory management, if /scalaropt=3 . INTEGER multiple division can be rotated into multiplication.