I think that your original interpretation of the wording was correct, and is the intent of the library, and on Windows, clock does indeed measure elapsed time http://msdn2.microsoft.com/en-us/library/4e2ess30(VS.71).aspx Stroustrup suggests that clock can be used to be used to measure elapsed time in The C++ Programming Language. But like you, I found that is not how it works for Posix, and the different behaviours make clock (and libraries that use it) unhelpful for anything intended to be cross platform. Did you have any success using date_time to measure short durations precisly? Could you post a short example? Regards, Steven Ruediger Berlich wrote:
Hi again,
apologies - probably my last posting was a stupid one. I had interpreted "The timer library supplies a timer class for measuring elapsed time" in such a way that the library can be used to measure a given amount of real time. However, the library internally uses the clock() call, which "returns an approximation of processor time used by the program". As I have just used usleep calls to simulate activity, the timer always returned 0. I will use the date_time library now instead, as my application spends a lot of time being idle.
Thanks and Best Regards, Ruediger
Ruediger Berlich wrote:
Hi there, the following program
/****************************************************/
#include <iostream> #include
using namespace std;
boost::timer t;
main() { t.restart(); for(int i=0; i<5; i++){ usleep(500000); cout << t.elapsed() << endl << t.elapsed_min() << endl << t.elapsed_max() << endl; } }
/****************************************************/
gives five times the following output, in 0.5 s intervals:
0 1e-06 9.22337e+12
I have tried the timer_test.cpp application (from http://www.boost.org/libs/timer/index.html). Most of it seems to be working, but the first messages also say:
timer::elapased_min() reports 1e-06 seconds timer::elapased_max() reports 9.22337e+12 seconds, which is 2.56205e+09 hours
After this the output seems to be fine.
So something clearly is wrong. Any ideas ?
This is on an OpenSuSE 10.2 system with a Boost 1.34.0 (with added ASIO support, 0.38rc3). g++ is 4.1.2 .
Thanks and Best Regards, Ruediger