If you need more accuracy for modern x86 CPUs, it is relatively easy to make an implementation of timer that uses the performance counter. Here is how to read the timer and get the period in Windows: period() { DWORD BufSize = _MAX_PATH; DWORD dwMHz = _MAX_PATH; HKEY hKey; // open the key where the proc speed is hidden: //long lError = RegOpenKeyEx(HKEY_LOCAL_MACHINE, LPCTSTR("HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0"), 0, KEY_READ, &hKey); // query the key: RegQueryValueEx(hKey, LPCTSTR("~MHz"), NULL, NULL, (LPBYTE) &dwMHz, &BufSize); value_ = 1./(dwMHz*1000000); } }; __forceinline static ULARGE_INTEGER readTimer() { #ifdef _WIN64 return __rdtsc(); #else ULARGE_INTEGER retval; unsigned int LowPart; unsigned int HighPart; __asm{ xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx _emit 0x0f // RDTSC _emit 0x31 mov [LowPart], eax // TICK COUNTER STARTS HERE mov [HighPart], edx // TICK COUNTER STARTS HERE } retval.LowPart = LowPart; retval.HighPart = HighPart; return retval; #endif } -----Original Message----- From: boost-bounces@lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of Howard Hinnant Sent: Tuesday, January 03, 2006 10:19 PM To: boost@lists.boost.org Subject: Re: [boost] Performance test and memory usage On Jan 3, 2006, at 5:12 PM, axter wrote:
What boost libraries are available for running code performance test
There is timer: http://www.boost.org/libs/timer/timer.htm which is very handy, but in my experience not a complete solution for performance testing on modern machines because of the variability of the results. I've had good experience with the following timer driver: template <class F> float test(F f) { std::vector<float> t; int i; for (i = 0; i < 10; ++i) t.push_back(f()); double total_time = std::accumulate(t.begin(), t.end(), 0.0); while (i < 1000 && total_time < 1.0) { t.push_back(f()); total_time += t.back(); ++i; } std::sort(t.begin(), t.end()); t.resize(t.size() * 9 / 10); return (float)(std::accumulate(t.begin(), t.end(), 0.0) / t.size ()); } Which can be used like: float time_something() { // whatever set up needs to happen clock_t t = clock(); // or boost::timer, or whatever { // time this } // scope to time any destructors as appropriate t = clock() - t; // or whatever // whatever tear down needs to happen return (float)(t/(double)CLOCKS_PER_SEC); return seconds (or whatever) as a float } int main() { cout << test(time_something) << '\n'; } The basic idea of "test" is to call the function to be timed many times (say up to 1000), throw away the slowest 10% of those times, and average the rest. Why? <shrug> shoot-from-the-hip "theory" and experience that its return is fairly consistent to 2, maybe 3 digits. The test function has a "time out" feature where it quits if the accumulated measured time grows beyond 1 second (which may not be appropriate for all tests). But it is easy to get bored when you unexpectedly find yourself waiting 30 minutes for timing result, so that's why it's there. Otoh, I put in a minimum repetition of at least 10, no matter how long the measured time is, so you get at least some accuracy (tweak knobs as you like). Note that the accumulation/averaging happens in double, even though the data and answer are float (just paranoia really). Weakness: If you're timing something that is quicker than the minimum resolution of your timer, this doesn't work. But otherwise, this is better than the traditional loop inside the timer as it throws away those results that happen to get interrupted by your email checker running. :-) Anyway, if it is useful to you, use it. If not, no sweat.
and memory usage (if any)?
If you limit it to new/delete (neglecting malloc), the following would be easy to adapt: http://groups.google.com/group/codewarrior.mac/browse_frm/thread/ efb176352c161b08/0faec33468b1d6bd?lnk=st&q=insubject%3Aworld's +insubject%3Asimplest+author%3Ahinnant&rnum=2&hl=en#0faec33468b1d6bd (some day I'm going to have to start using tinyurl (or whatever it is)). The above is just an overloaded new using hash_map<void*, mem_info, malloc_allocator<appropriate pair> >. (map could just as easily be used). You could collect statistics from the container, and from mem_info. The malloc_alloc is necessary so that the container itself doesn't pollute your measurement. -Howard _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost