struct Mtimer
{
__int64 start; // Start time, in counts
__int64 end; // End time, in counts
__int64 freq; // Count frequency (per second)
__int64 elapsed; // Time elapsed, in counts
};
Mtimer *mTimer;
void mInitTimer()
{
QueryPerformanceFrequency(mTimer->freq);
QueryPerformanceCounter(mTimer->start);
}
void mUpdateTimer()
{
QueryPerformanceCounter(mTimer->end);
mTimer->elapsed = mTimer->end - mTimer->start;
mTimer->start = mTimer->end;
}
QueryPerformanceCounter anyone?
Author
QueryPerformanceCounter() is supposed to be much more precise than GetTickCount() on pc systems so I am tring to implement a timer using this function. Unfortunately, it does seem quite complex and I have not found any simple implementation on the net. Here is what I am trying to do:
Just create a LARGE_INTEGER and use the QuadPart component of its union (which is of type __int64) whenever you do calculations. I don''t recommend just type-casting an __int64 to a LARGE_INTEGER when passing it even though you should get the same results. Try not to use type-casting when it is not necessary.
Author
Thanks Polymorphic, I did as you suggested, but why do I get this?? (end time is always 7 and frequancy varies with start time, when it should be constant...)
Logfile created on Sat Oct 11 00:26:12 2003
-------------------------------------------
Timer start: -1638143324 end: 7 freq: 0 elapsed: 0
Timer start: -1638141830 end: 7 freq: -1638141830 elapsed: 7
Timer start: -1638068676 end: 7 freq: -1638068676 elapsed: 7
Timer start: -1638008203 end: 7 freq: -1638008203 elapsed: 7
Timer start: -1637950592 end: 7 freq: -1637950592 elapsed: 7
[edited by - Keermalec on October 10, 2003 6:49:11 PM]
Logfile created on Sat Oct 11 00:26:12 2003
-------------------------------------------
Timer start: -1638143324 end: 7 freq: 0 elapsed: 0
Timer start: -1638141830 end: 7 freq: -1638141830 elapsed: 7
Timer start: -1638068676 end: 7 freq: -1638068676 elapsed: 7
Timer start: -1638008203 end: 7 freq: -1638008203 elapsed: 7
Timer start: -1637950592 end: 7 freq: -1637950592 elapsed: 7
struct Mtimer{ LARGE_INTEGER start; // Start variable, in counts LARGE_INTEGER end; // End variable, in counts LARGE_INTEGER freq; // Count frequency (per sec) __int64 elapsed; // Time elapsed, in counts};Mtimer *mTimer;void mInitTimer(){ mTimer = new Mtimer; QueryPerformanceFrequency( &mTimer->freq ); QueryPerformanceCounter( &mTimer->start ); mPrintLog();}void mUpdateTimer(){ QueryPerformanceCounter( &mTimer->end ); mTimer->elapsed = mTimer->end.QuadPart - mTimer->start.QuadPart; mTimer->start.QuadPart = mTimer->end.QuadPart; mPrintLog();}void mPrintLog(){ fprintf(mFile, "\nTimer start: %i end: %i freq: %i elapsed: %i", mTimer->start.QuadPart, mTimer->end.QuadPart, mTimer->freq.QuadPart, mTimer->elapsed );}[edited by - Keermalec on October 10, 2003 6:49:11 PM]
quote:Original post by Keermalec
Thanks Polymorphic, I did as you suggested, but why do I get this?? (end time is always 7 and frequancy varies with start time, when it should be constant...)
Logfile created on Sat Oct 11 00:26:12 2003
-------------------------------------------
Timer start: -1638143324 end: 7 freq: 0 elapsed: 0
Timer start: -1638141830 end: 7 freq: -1638141830 elapsed: 7
Timer start: -1638068676 end: 7 freq: -1638068676 elapsed: 7
Timer start: -1638008203 end: 7 freq: -1638008203 elapsed: 7
Timer start: -1637950592 end: 7 freq: -1637950592 elapsed: 7
struct Mtimer{ LARGE_INTEGER start; // Start variable, in counts LARGE_INTEGER end; // End variable, in counts LARGE_INTEGER freq; // Count frequency (per sec) __int64 elapsed; // Time elapsed, in counts};Mtimer *mTimer;void mInitTimer(){ mTimer = new Mtimer; QueryPerformanceFrequency( &mTimer->freq ); QueryPerformanceCounter( &mTimer->start ); mPrintLog();}void mUpdateTimer(){ QueryPerformanceCounter( &mTimer->end ); mTimer->elapsed = mTimer->end.QuadPart - mTimer->start.QuadPart; mTimer->start.QuadPart = mTimer->end.QuadPart; mPrintLog();}void mPrintLog(){ fprintf(mFile, "\nTimer start: %i end: %i freq: %i elapsed: %i", mTimer->start.QuadPart, mTimer->end.QuadPart, mTimer->freq.QuadPart, mTimer->elapsed );}
[edited by - Keermalec on October 10, 2003 6:49:11 PM]
If I''m reading MSDN correctly,
the numbers may be printing incorrectly because the QuadParts are 64 bits and %i is for 32 bit numbers. So according to MSDN, try %I64i instead.
Author
OMG, CrazyMike, you are so right! %i is limited to 32-bit numbers and %I64i should be used instead. My timer now works beautifully fine, thanks a lot. Now why can I not find any reference to %I64i in my MSVC6 doc?...
MVE logfile created on Mon Oct 13 08:08:27 2003
-----------------------------------------------
Timer start: 8153306016 end: 0 freq: 3579545 elapsed: 0
Timer start: 8153307509 end: 8153307509 freq: 3579545 elapsed: 1493
Timer start: 8153412759 end: 8153412759 freq: 3579545 elapsed: 105250
Timer start: 8153475285 end: 8153475285 freq: 3579545 elapsed: 62526
Timer start: 8153529982 end: 8153529982 freq: 3579545 elapsed: 54697
MVE logfile created on Mon Oct 13 08:08:27 2003
-----------------------------------------------
Timer start: 8153306016 end: 0 freq: 3579545 elapsed: 0
Timer start: 8153307509 end: 8153307509 freq: 3579545 elapsed: 1493
Timer start: 8153412759 end: 8153412759 freq: 3579545 elapsed: 105250
Timer start: 8153475285 end: 8153475285 freq: 3579545 elapsed: 62526
Timer start: 8153529982 end: 8153529982 freq: 3579545 elapsed: 54697
This topic is closed to new replies.
Advertisement
Popular Topics
Advertisement
