-fsimple=2

Unless directed to, the compiler does not attempt to simplify floating-point computations (the default is -fsimple=0). With the -fast option, -fsimple=1 is used and some conservative assumptions are made. Adding -fsimple=2 enables the optimizer to make further simplifications with the understanding that this might cause some programs to produce slightly different results due to rounding effects. If -fsimple level 1 or 2 is used, all program units should be similarly compiled to ensure consistent numerical accuracy.