elapsed time in microseconds, VC++

[zaga]

Hi

I'm using VC++ Express, im trying to get elapsed time in microseconds
for consol app. . i tryed the clock function but it didn't show the time in microseconds.

[Siddhartha]

Well, Windows is not a Real Time Operating System.... Even when you manage to get the elapsed time in microseconds, you will not get the accuracy you are looking for.

You can use GetTickCount API to get time elapsed in msecs. Another option is the Timer Classes in this FAQ to get results as well.

[TheCPUWizard]

Siddhartha is right. Any numbers you tried to get would be meaningless.

But:

double uS = (clock() / CLKS_PER_SEC) * 1000000;

Will give that numeric quantity...

[Pravin Kumar]

Hello,

GetTickCount and timers will not be of help, if you want to measure time between events to an accuracy of microsec. GetTickCount function have an accuracy of millisec only. Timers have low priority. What you have to use is the high resolution performance counter.

The FAQ How do I evaluate the time difference between two events? may be helpful.

Regards,
Pravin.

[TheCPUWizard]

Hello,

GetTickCount and timers will not be of help, if you want to measure time between events to an accuracy of microsec. GetTickCount function have an accuracy of millisec only. Timers have low priority. What you have to use is the high resolution performance counter.

The FAQ How do I evaluate the time difference between two events? may be helpful.

Regards,
Pravin.

Which is exactly what we have all been saying. However there are a few (albiet almost all ill-concieved) where it is desired to express a measurement in units that are not appropriate, but are mathematically valid.

For example.

X occurs once a day +/- 10 minutes.

X occurs every 86400000000uS +/- 600000000uS

Both are equally valid from every point of view. But the first "makes more sense".

[Siddhartha]

timers will not be of help

[...]

The FAQ How do I evaluate the time difference between two events? may be helpful.

Pravin, the timer class in the FAQ presented above does exactly what your FAQ does (QueryPerformance* APIs).