So the code compiles and executes without errors? It works perfectly?
In that case, the next aspect I might consider is that perhaps the section of code you are testing executes so fast, the result rounds to zero. Are you sure the code does not execute nearly instantaneously? Perhaps compute a transcendental function like sin(x) a thousand times to give it a bit of a work out. Then you should know for sure that execution is taking some time. If the result is still 0, then I am not sure what else to suggest.