performance of operator>>(istream&, double) VC10/VC11 - visual-studio-2010

Question

Switching from VC10 to VC11 I observe a performance drop of a factor 10 when reading a file with double numbers:
#include <iostream>
int main() {
double sum = 0, x;
for(int i=0; i<1000000; i++){
std::cin >> x;
sum += x;
}
std::cerr << sum << std::endl;
return 0;
}
I built the executable in Developer Studio, so that the environment chooses the options in release mode at best.
Can anybody confirm this?
What could be the problem? Might it be related to locale?
thanks in advance,
andreas

Answer 1

*for some reason my previous answer was deleted (I do admit that the first sentence was a bit confusing, due to a clumsy edit when it got better results)
Actually, for me the performance is about the same.
VC11 writing/reading 1M doubles -> 6.600/3.562 seconds
VC10 writing/reading 1M doubles -> 6.266/3.606 seconds
So in my experiment, reading doubles from file in vc11 is aprox. the same performance as with vc10.
Codesample:
int _tmain(int argc, _TCHAR* argv[])
{
auto x = 0.0;
auto numberofdoubles = 1000000;
auto filename = "C:\\double.txt";
{
std::ofstream filestr(filename);
auto starttime = clock();
for(int i=0; i<numberofdoubles; i++)
filestr << (double)i << " ";
auto endtime = clock();
auto elapsed = (double)(endtime - starttime)/CLOCKS_PER_SEC;
std::cout << "writing: " << elapsed << std::endl;
}
{
std::ifstream filestr (filename);
auto starttime = clock();
for(int i=0; i<numberofdoubles; i++)
filestr >> x;
auto endtime = clock();
auto elapsed = (double)(endtime - starttime)/CLOCKS_PER_SEC;
std::cout << "reading: " << elapsed << std::endl;
}
return 0;
}