clock cycle counter?

[micke_b]

Is there some function in c under linux that one can use to count clock cycles/nr of ticks? or similar? preferably in nano secs.

[foxman]

You'll never have nanoseconds precision, well not with the computer we are using these days.

I couldn't say if there's such function on Linux. I bet there is; someone else might answer you.

But if you can write assembly for IA-32 processor (or Intel 64 architecture processor), then you should look at the RDTSC (ReaD Time Stamp Counter) instruction.

[vart]

somthing like

inline unsigned long rdtsc()
{
#if defined(__ia64)
    /* for Intel Itanium 64 bit processor */
    unsigned long x;
    __asm__ __volatile__("mov %0=ar.itc" : "=r"(x) :: "memory");
    while (__builtin_expect ((int) x == -1, 0))
        __asm__ __volatile__("mov %0=ar.itc" : "=r"(x) :: "memory");
    return x;
#else
    /* for all others */
    unsigned long long x;
    unsigned int low,high;
    __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high));
    x = high;
    x = (x<<32)+low;
    return x;
#endif
}