Native C++ vs C++/CLI speeds

Hello everyone.

I have a question regarding C++/CLI vs Native C++ speeds. I have written a little test application and I am seeing very surprising results.

It seems that the unmanaged C++/CLI code is significantly slower. Basically I created two console apps. One a standard win32 console app and a CLR console app

Here is the code I did for a test. I kept the code exactly the same in all versions of the test.

const int NumberOfTests = 10000000;
void GrowBalance(int numberOfYears)
{
 std::cout<<"Called"<<std::endl;

 DWORD startTime = GetTickCount();

 int numberOfRandom = 0;
 for(int i = 0; i < NumberOfTests; i++)
 {
  double dBalance = 10000.0;
  for(int year = 0; year < numberOfYears; year++)
  { 
   dBalance *= 1.05;
   if(dBalance > 20000.00 && dBalance < 22000.00)
   {
    numberOfRandom++;
   }//if
  }//for
 }//for

 DWORD endTime = GetTickCount();

 std::cout<<"Time Elapsed: "<<endTime - startTime<<std::endl;
 std::cout<<"Number of random: "<<numberOfRandom<<std::endl;
}

Output managed code:

Called
Time Elapsed: 9937
Number of random: 20000000

Output managed code with pragma managed(push, off):

Called
Time Elapsed: 24516
Number of random: 20000000

Output native code:

Called
Time Elapsed: 2156
Number of random: 20000000

In the mains just calling GrowBalance with 90 years specified. Pretty basic test. Is there something I am doing wrong or am I really looking at code that is going to be 4.5 times slower by using C++/CLI. And I also don't understand the case of turning managed code off. Everything I have read said this would compile the code to native C++ but it is insanely slower.

Any help with this would be very much appreciated.

Thanks, Brian

Update: I just ran this test in visual studio 2005 instead of 2008. Native C++ performance is matched.

Update #2: I just put my test code into a class instead of a single function and am getting much better results. Now the mixed code is preforming at an average run time of ~5000ms

But in 2005 I am seeing much much faster results. Average run time of about ~1875ms. Maybe I will just stick to 2005 for my CLI development. Unless someone has a reason why this could be occurring.

ansaurus

tags:

views:

answers:

Native C++ vs C++/CLI speeds

related questions