-qstrict

However, in Open XL C/C++ for z/OS, -O3 does not enable most of the floating-point optimizations that z/OS XL C/C++ enabled. To enable more floating-point optimizations in Open XL C/C++ for z/OS, use the following steps:

1. Specify -O3 to let the program produce expected results.
2. Specify -Ofast to further optimize the program.
3. If correctness issues arise when moving from -O3 to -Ofast, selectively disable certain types of floating-point optimizations with one or more of the following options to achieve the balance between accuracy and speed.
   • -f[no-]honor-infinities
   • -f[no-]honor-nans
   • -f[no-]math-errno
   • -f[no-]finite-math-only
   • -f[no-]associative-math
   • -f[no-]reciprocal-math
   • -f[no-]signed-zeros
   • -f[no-]trapping-math
   • -ffp-contract
   • -f[no-]rounding-math