hi resolution timer questions 1

[jsmokey]

hi, I would like to use a high resolution timer to time some disk accesses. I want to do this in a loop where i start the timer, do a random access of a file, stop the timer, add the number in nanoseconds to the running total for averaging later. The pseudocode looks like this

for i = 1 to 100
start timer
tell it where to go in diskspace
read a few characters
stop timer
add the time i got in this pass to the running total

next i

I know how to do everything except the timer. Ive never used a timer before and im not too fermilliar with c programming for linux or cygwin. Does anyone know how to set up the timer, what libraries i need, how to start it and stop it and how to save the time in some sort of variable? thanks in advance

 

[Salem]

There is the gettimeofday function which returns time with a precision of microseconds.
However, the accuracy is unspecified (it could just bump the microsecond count by 1000 every millisecond).

For a really fast and really accurate clock, then there is the rdtsc instruction for pentium users.

--

 

[maur3r]

If you are running on solaris you can try

http://courses.cs.tamu.edu/cpsc612/miket/notes/clock.html

The other option is to use traditional clock() function. It's obviously less accurate that the ones mentioned by Salem.
This is about clock()

clock_t start, finish;
double duration;
start=clock();
/* your loop */
finish=clock();
duration=(double)(finish -start)/CLOCKS_PER_SEC;

Also here are some links to similar topics.

http://www.tek-tips.com/viewthread.cfm?qid=1284674&page=2

http://www.tek-tips.com/viewthread.cfm?qid=1295501&page=1

Regards, Martin

(OS and comp.)
using Linux and gcc