1. one variable value is 2.468057e-18for O0 and 1.676039e-18for O3.
This variable looks very small.
"Small" compared to what? 1 ? How about compared to 0 ? The diameter of an electron in light-years ? 2. variable F=4867459.8367both for O0 and O3 While F-ksi=-9.31323e-10 for O0 and -1.86265e-09 for O3
... then F-ksi e-9 should not make sense at all.
We have no idea what "F-ksi" is; therefore, any judgements about its value making sense are premature. But how to eliminate these differences from compiler site?
You cannot, except in a contrived and pointless way. You would benefit by reading books and articles about what to expect from finite-precision calculations. For starters, Google "perfidious polynomial" and read some of the articles related to that.