David, thank you four your answer. "Dr. David Kirkby" <david.kirkby@xxxxxxxxxx> writes: > Christoph Groth wrote: > >> If I take the second (-O1) binary and execute it on an Opteron it >> produces the _first_ result. Thus, the same static binary produces >> different results on different processors! > > That is not unusual. The 64-bits only give a precision of about 15-16 > decimal places, so you can't necessarily expect identical results on > different processors. I am aware of the limited precision of floating point calculations. However, I assumed that on the processors in question these calculations are done according to IEEE standards, i.e. the results of are defined unambiguously. I further assumed that gcc is always supposed to produce the same results (with the exception of things like -ffast-math and the 80-64-bit rounding issue on x87 (which are not applicable here)). Certainly, I assumed that the same static binary will produce the same results on processors with the same instruction set (x86-64 here).
