Why is .NET faster than C++ in this case?

Question

Make sure you run outside of the IDE. That is key.

-edit- I LOVE SLaks comment. \"The amount of misinformation in these answers is staggering.\" :D

Answer 1

EDIT: While the original C++ timing is wrong (comparing cycles to milliseconds), better timing does show C# is faster with vanilla compiler settings.

OK, enough random speculation, time for some science. After getting weird results with existing C++ code, I just tried running:

int fib(int n)
{
    if (n < 2) return n;
    return fib(n - 1) + fib(n - 2);
}

int main()
{
    __int64 time = 0xFFFFFFFF;
    while (1)
    {
        int n;
        //cin >> n;
        n = 41;
        if (n < 0) break;
        LARGE_INTEGER start, end, delta, freq;
        ::QueryPerformanceFrequency( &freq );
        ::QueryPerformanceCounter( &start );
        int res = fib(n);
        ::QueryPerformanceCounter( &end );
        delta.QuadPart = end.QuadPart - start.QuadPart;
        cout << res << endl;
        cout << ( delta.QuadPart * 1000 ) / freq.QuadPart <

EDIT:

MSN pointed out you should time C# outside the debugger, so I re-ran everything:

Best Results (VC2008, running release build from commandline, no special options enabled)

• C++ Original Code - 10239
• C++ QPF - 3427
• C# - 2166 (was 4700 in debugger).

The original C++ code (with rdtsc) wasn't returning milliseconds, just a factor of reported clock cycles, so comparing directly to StopWatch() results is invalid. The original timing code is just wrong.

Note StopWatch() uses QueryPerformance* calls: http://msdn.microsoft.com/en-us/library/system.diagnostics.stopwatch.aspx

So in this case C++ is faster than C#. It depends on your compiler settings - see MSN's answer.