C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Timing question          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Tyler Guest Posted: Tue Oct 14, 2003 9:08 pm    Post subject: Timing question Hi, I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. Tyler [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jack Klein Guest Posted: Wed Oct 15, 2003 10:46 am    Post subject: Re: Timing question On 14 Oct 2003 17:08:38 -0400, [email]hobbit_jr (AT) yahoo (DOT) com[/email] (Tyler) wrote in comp.lang.c++.moderated: Quote: Hi, I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. Tyler There are no standard functions in the C or C++ library that can do this. Many compilers provide their own particular extensions to provide higher resolution, but they can be very different from one compiler/operating system combination to the next. You really need to ask in a group that supports your particular compiler and platform to find out what features, if any, if provides. -- Jack Klein Home: http://JK-Technology.Com FAQs for comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html comp.lang.c++ http://www.parashift.com/c++-faq-lite/ alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Sean Fraley Guest Posted: Wed Oct 15, 2003 12:53 pm    Post subject: Re: Timing question Tyler wrote: Quote: Hi, I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. You'll have to go into the OS api for something along that line. Boost has a library that might be of some use to you. http://www.boost.org/libs/timer/index.htm Sean [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Peter van Merkerk Guest Posted: Wed Oct 15, 2003 10:03 pm    Post subject: Re: Timing question Quote: I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. Possibly the clock() function has a higher resolution on your platform. If the resolution of clock() function is not sufficient I'm afraid you will have to resort to platform specific functions. -- Peter van Merkerk peter.van.merkerk(at)dse.nl [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top kanze@gabi-soft.fr Guest Posted: Wed Oct 15, 2003 10:36 pm    Post subject: Re: Timing question [email]hobbit_jr (AT) yahoo (DOT) com[/email] (Tyler) wrote in message news:<fb057608.0310140335.247a9c4f (AT) posting (DOT) google.com>... Quote: I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. There's nothing standard for this, so you'll have to check with your implementation and/or environment. (Under Unix, there is gettimeofday, which will give you the maximum resolution available -- unless that resolution is less than a microsecond. I presume that there is something similar under Windows, and probably under most other systems as well.) -- James Kanze GABI Software mailto:kanze (AT) gabi-soft (DOT) fr Conseils en informatique orientée objet/ http://www.gabi-soft.fr Beratung in objektorientierter Datenverarbeitung 11 rue de Rambouillet, 78460 Chevreuse, France, +33 (0)1 30 23 45 16 [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Siemel Naran Guest Posted: Thu Oct 16, 2003 2:21 pm    Post subject: Re: Timing question "Tyler" <hobbit_jr (AT) yahoo (DOT) com> wrote in message Quote: I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. Did you try the function clock_t clock(); For me, clock_t is long and represents milliseconds. I'm not sure if this holds across all platforms though. -- +++++++++++ Siemel Naran [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ben Hutchings Guest Posted: Thu Oct 16, 2003 2:30 pm    Post subject: Re: Timing question In article <fb057608.0310140335.247a9c4f (AT) posting (DOT) google.com>, Tyler wrote: Quote: Hi, I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. clock() normally has resolution smaller than a second (CLOCKS_PER_SEC specifies just how precise it is). Also, whereas comparing values returned by time() will tell you the time elapsed, clock() is defined to return "the implementation's best approximation to" the processor time used, which in a multitasking and/or multiprocessor system is of course something different. Note that Microsoft's implementation of clock() actually returns elapsed time since the start of the process, just as it would under DOS! For more precise measurements, you could use the following non- portable functions: Elapsed time Processor time Unix gettimeofday times Windows GetLocalTime, GetProcessTimes, GetSystemTime, GetThreadTimes GetSystemTimeAsFileTime [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Tony Oliver Guest Posted: Thu Oct 16, 2003 2:41 pm    Post subject: Re: Timing question [email]hobbit_jr (AT) yahoo (DOT) com[/email] (Tyler) wrote Quote: I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. You shouldn't be using <time.h> - this is a C header file (deprecated in C++). C++ encapsulates the time API in header <ctime>, which you should use. In there, you will find clock_t, clock() and CLOCKS_PER_SEC declared/defined. Put them together like this: #include <ctime> #include <iostream> extern void do_long_process(); int main() { clock_t start = clock(); do_long_process(); clock_t finish = clock(); double elapsed_time = double(finish - start) / CLOCKS_PER_SEC; std::cout << "The long process took " << elapsed_time << " seconds." << std::endl; return 0; } The granularity of clock() is generally much better than that of time(). A simple test program can easily detect what that precision is on your particular target platform. Hope this helps. Best regards, Tony. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Antoun Kanawati Guest Posted: Thu Oct 16, 2003 3:35 pm    Post subject: Re: Timing question Tyler wrote: Quote: Hi, I'm trying to time my C++ program but the standard "time.h" library only gives precision of up to seconds. I'm looking for greater precision, maybe in terms of milliseconds or better (i.e. 2.13456 s for example). Anyone knows how I can go about doing this? Many thanks in advance. On Win32, the ftime() function yields millisecond resolution. There's probably something like it on Unix/Linux. The lazy way is to download Time::HiRes from CPAN, and look at the source code (it's a Perl module that provides microsecond resolution, where available). The module is a mixture of Perl and C. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Francis Glassborow Guest Posted: Thu Oct 16, 2003 8:41 pm    Post subject: Re: Timing question In article <4a81d9f8.0310150651.15c035f5 (AT) posting (DOT) google.com>, Tony Oliver <tony.xt.oliver (AT) ericsson (DOT) com> writes Quote: You shouldn't be using <time.h> - this is a C header file (deprecated in C++). C++ encapsulates the time API in header <ctime>, which you should use. In there, you will find clock_t, clock() and CLOCKS_PER_SEC declared/defined. Using time.h is absolutely fine and will provide you exactly the same functionality that you get from ctime. The only difference is in regard to whether namespace std is required explicitly. -- Francis Glassborow ACCU If you are not using up-to-date virus protection you should not be reading this. Viruses do not just hurt the infected but the whole community. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Alex Vinokur Guest Posted: Fri Oct 17, 2003 2:34 am    Post subject: Re: Timing question "Ben Hutchings" <do-not-spam-benh (AT) bwsint (DOT) com> wrote [snip] Quote: For more precise measurements, you could use the following non- portable functions: Elapsed time Processor time Unix gettimeofday times Also getrusage(). [snip] -- ===================================== Alex Vinokur mailto:alexvn (AT) connect (DOT) to http://mathforum.org/library/view/10978.html news://news.gmane.org/gmane.comp.lang.c++.perfometer ===================================== [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Siemel Naran Guest Posted: Fri Oct 17, 2003 11:10 am    Post subject: Re: Timing question "Tony Oliver" <tony.xt.oliver (AT) ericsson (DOT) com> wrote in message Quote: #include <ctime #include extern void do_long_process(); int main() { clock_t start = clock(); As you include std::clock_t start = std::clock(); ? -- +++++++++++ Siemel Naran [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Alex Vinokur Guest Posted: Sat Oct 18, 2003 9:17 am    Post subject: Re: Timing question "Tony Oliver" <tony.xt.oliver (AT) ericsson (DOT) com> wrote [snip] Quote: The granularity of clock() is generally much better than that of time(). A simple test program can easily detect what that precision is on your particular target platform. time() and clock() return different values : * time() returns elapsed (_wall clock_) time, * clock() returns cumulative _processor_ time. Here is a sample. ============================== GNU gcc version 3.3.1 (cygming special) ============================== ========= C++ code : File t.cpp : BEGIN ========= #include <time.h> #include <unistd.h> // UNIX #include <assert.h> #include <iostream> using namespace std; int main() { time_t start_time, end_time; clock_t start_clock, end_clock; clock_t diff_clock; time_t diff_time; start_time = time(NULL); if (start_time == time_t(-1)) { cout << "Unable to get start time()" << endl; return 1; } start_clock = clock(); if (start_clock == clock_t(-1)) { cout << "Unable to get start clock()" << endl; return 1; } sleep (3); // UNIX, system call end_time = time(NULL); if (end_time == time_t(-1)) { cout << "Unable to get end time()" << endl; return 1; } end_clock = clock(); if (end_clock == clock_t(-1)) { cout << "Unable to get end clock()" << endl; return 1; } // ------------------------- assert (!(start_time == (time_t)-1)); assert (!(end_time == (time_t)-1)); assert (!(start_clock == (clock_t)-1)); assert (!(end_clock == (clock_t)-1)); // ------------------------- diff_time = end_time - start_time; diff_clock = end_clock - start_clock; cout << endl; cout << "time : " << "start = " << start_time << " sec" << ", end = " << end_time << " sec" << endl; cout << "time : " << "elapsed (wall clock) time = " << double (diff_time) << " sec" << endl; cout << endl; cout << "clock : " << "start = " << start_clock << " ticks" << ", end = " << end_clock << " ticks" << endl; cout << "clock : " << "cumulative processor time = " << double(diff_clock)/CLOCKS_PER_SEC << " sec" << endl; return 0; } ========= C++ code : File t.cpp : END =========== ========= Compilation & Run : BEGIN =========== $ g++ t.cpp $ a time : start = 1066416574 sec, end = 1066416577 sec time : elapsed (wall clock) time = 3 sec clock : start = 10 ticks, end = 20 ticks clock : cumulative processor time = 0.01 sec ========= Compilation & Run : END ============= -- ===================================== Alex Vinokur mailto:alexvn (AT) connect (DOT) to http://mathforum.org/library/view/10978.html news://news.gmane.org/gmane.comp.lang.c++.perfometer ===================================== [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Alex Vinokur Guest Posted: Sat Oct 18, 2003 10:14 pm    Post subject: Re: Timing question "Alex Vinokur" <alexvn (AT) bigfoot (DOT) com> wrote [snip] Quote: * time() returns elapsed (_wall clock_) time, [snip] Sorry, * `time' -- get current calendar time (as single number) - from 'man time'. Returned value is number of seconds. Elapsed (_wall clock_) time is = end_current_calendar_time - start_current_calendar_time. -- ===================================== Alex Vinokur mailto:alexvn (AT) connect (DOT) to http://mathforum.org/library/view/10978.html news://news.gmane.org/gmane.comp.lang.c++.perfometer ===================================== [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. 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