Philippe Vaucher wrote:
3. Does anyone know if std::clock() isn't implemented on "linux" ? On the unbuntu and gentoo boxes I tried it keeps returning 0, while on windows it works.
It is implemented and works. I've got a 2.6.14 kernel 64-bit Gentoo with a 2.5 glibc. #include <ctime> #include <cmath> #include <iostream> #include <ostream> int main() { std::cout << "Start: " << std::clock() << std::endl; for(int i = 0; i < 10000; ++i) { double foo = std::sqrt(static_cast<double>(i)); std::cout << foo << "\b\b\b\b\b\b\b\b\b\b\b\b\b" << std::flush; } std::cout << "End: " << std::clock() << std::endl; } The program's output varies between 20000 and 90000. The first one is always 0. clock() is supposed to measure elapsed CPU time, but the initial value is unspecified. It's apparently always 0 in Linux. The resolution doesn't seem to be very high, though. Given that CLOCKS_PER_SEC is defined by POSIX to be 1000000 regardless of actual resolution, and given that the values are always "rounded" to steps of ten thousand, I'd guess the resolution is 100Hz. This is not as good as the kernel timer resolution of 1000Hz that I have configured. Sebastian Redl