how to avoid the potential of an overflow when computing an average of times?

Question

I am writing a function for getting the average of the clocks it takes to call a specific void (*)(void) aka void -> void function a specific number

Answer 1

You can reduce potential for overflow by adding to sum the value dt/nSamples while making sure that you don't lose dt%nSamples.

template 
static inline ULONGLONG AveragePerformanceClocks (void (*f)(),
                                                  sampleunit_t nSamples)

{
    ULONGLONG delta = 0;
    ULONGLONG sum = 0;
    sampleunit_t i;    

    for (i = 0; i < nSamples; ++i) {
        LARGE_INTEGER t1; 
        LARGE_INTEGER t2;
        ULONGLONG dt;

        QueryPerformanceCounter(&t1);
        f();        
        QueryPerformanceCounter(&t2);

        dt = t2.QuadPart - t1.QuadPart;

        // Reduce the potential for overflow.
        delta += (dt%nSamples);
        sum += (dt/nSamples);
        sum += (delta/nSamples);
        delta = (delta%nSamples);
    }

    return sum;
}