As long as the you use only the four elementary arithmetic operations in the same order with the same types, and use compiler flags that disables any optimisati

As long as the you use only the four elementary arithmetic operations in the same order with the same types, and use compiler flags that disables any optimisations, then you should get the same result. (knock on wood) Different standard libraries for different processors could have different precision for transcendental functions though. There are those that are written to always produce reproducible results though; and in the case of CRlibm, proven correctly rounded. Older compilers for x86 used the x87 FPU which used a 80-bit type internally but all modern compilers for x86 and x86-64 use SSE/AVX instead which supports IEEE types.