How can I get a difference between two DateTime intervals in micro and nano seconds?

[srikanth]

am getting milliseconds like this

quint64 ITime::elapsed()
{
oEndTime = QDateTime::currentDateTime();
quint64 elapsed = qAbs(oStartTime.date().daysTo(oEndTime .date()));
elapsed *= static_cast<quint64>(24); // days to hours
elapsed *= static_cast<quint64>(60); // hours to minutes
elapsed *= static_cast<quint64>(60); // minutes to seconds
elapsed *= static_cast<quint64>(1000); // seconds to milliseconds
elapsed += qAbs(oStartTime.time().msecsTo(oEndTime .time()));
return elapsed;
}

am getting milliseconds here , but i want micro and nano seconds in difference .

am using Qt 4.3.2 version , in visual studio 2005.

[SGaist]

Hi,

You can't, dates are calculated as milliseconds since epoch.

If you want something with a higher level of details to measure a duration then you should take a look at std::chrono::duration.

Note that you are currently developing with a pretty outdated version of Qt as well as compiler. If possible, you should upgrade.

[srikanth]

@SGaist chrono is not working for me
i try like this with #include <chrono>

	auto start = std::chrono::high_resolution_clock::now();

	auto finish = std::chrono::high_resolution_clock::now();
	std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(finish-start).count() << "ns\n";

[mrjj]

in what way "not working" ?

#include <iostream>
#include <chrono>
using namespace std;
 
int main()
{
	cout << chrono::high_resolution_clock::period::den << endl;
	auto start_time = chrono::high_resolution_clock::now();
	int temp;
	for (int i = 0; i< 242000000; i++)
		temp+=temp;
	auto end_time = chrono::high_resolution_clock::now();
	cout << chrono::duration_cast<chrono::seconds>(end_time - start_time).count() << ":";
	cout << chrono::duration_cast<chrono::microseconds>(end_time - start_time).count() << ":";
	return 0;
}

[srikanth]

@mrjj fatal error C1083: Cannot open include file: 'chrono': No such file or directory
error is showing like this

[mrjj]

@srikanth
Ok, sounds like you dont have it then.
VS 2005 is epic old compiler wise.
Its not possible to use c++11 with it.

[srikanth]

@mrjj is there any way to get precision time difference (micro & nano) in my environment , am struck here , please help me to get out from this , thanks in advance :)

[mrjj]

@srikanth
Im not sure nano is an option unless high precision timer is available.

You can google on ways to time functions etc in c++
Sounds like you want something like that
http://stackoverflow.com/questions/15092504/how-to-time-a-function-in-milliseconds-without-boosttimer

There are also native windows functions etc but i do not know what task or requirements you have.

There are a lot on google.

[VRonin]

boost chrono is an option, I don't think it needs C++11.

Do you need to get the difference between 2 timers (so you have to get the current time) or is it the difference of some static data-points you have? in the second case you can handle it quite simply manually

[J.Hilk]

You can use

#include <QElapsedTimer>

its has the function

qint64 QElapsedTimer::nsecsElapsed() const

that is nano seconds since last started.
Available since Qt 4.7.

[SGaist]

That's what I would have proposed except his environment uses Qt 4.3.2

[J.Hilk]

@SGaist
Oh, I missed that, sorry.
For some reason all I thought was "pre Qt5.0 so it fits" .

[mrjj]

Hi
He is trying the boost chrono as @VRonin suggest but
im not sure building it with VS 2005 is great joy. ? :)

[VRonin]

@mrjj The current release uses C++11 but boost version 1.47.0 does not. I also think boost::chrono and std::chrono are the same thing

[mrjj]

@VRonin
Ah and such old version might have makefile for Vs 2005 included.
We cross fingers :=)

[srikanth]

can i use chrono in VS 2005 , am unable to get nanoseconds is there anyway to get nanoseconds in vs 2005 & Qt 4.3.2

[jsulm]

@srikanth As @VRonin said you can use Boost 1.47.0 (boost::chrono: https://theboostcpplibraries.com/boost.chrono).

[srikanth]

@jsulm i downloaded the boost.zip file from this link
[http://www.boost.org/users/history/version_1_63_0.html]

unzip them and then add something like INCLUDEPATH += C:/boost/boost_1_63_0/ to my pro file , if i run this code then it is getting error like this "fatal error LNK1104: cannot open file 'libboost_chrono-vc80-mt-gd-1_63.lib' " so what can i do now ? to get this lib file .

[mrjj]

@srikanth
Try the 1.47.0 one.
1_63 might be too new for VS 2005.

[jsulm]

@srikanth You need to link to the library mentioned in the error message:

LIBS += -LPATH_TO_BOOST_LIBS -lboost_chrono-vc80-mt-gd-1_63