Hello, I have some Fortran 77 code like this (it's not me who wrote it) -- c f1 and f2 are of the same floating point type c func() returns the same value on every call 10 f1 = func() 20 f2 = func() c f1 and f2 are expected to have the same value 30 if (f1 - f2) 100,200,300 When compiled without optimization, the "if" branches to line 200 as expected. When compiled with optimization, at line 30 the value of f2 still remains in the register, which has extended precision, and f1 has already been truncated. Therefore, line 30 will branch to anywhere depending on the rounding of f1. My question is: Does "gfortran -O0" guarantee that both f1 and f2 are truncated by line 30, so they compare equal? Thanks in advance! Guan
