#include <stdio.h>
#include <math.h>

int main( int argc, const char *const* argv )
{
  unsigned long tsc_lo, tsc_hi, tsc_cpu;
  int cnt=10;
  unsigned long sample[10], s=0, last_tsc=0;
 do_it:
  (tsc_lo = tsc_hi =0, tsc_cpu=~0);
  asm volatile
    ( "rdtscp"
    : "=a" (tsc_lo) ,
      "=d" (tsc_hi) ,
      "=c" (tsc_cpu)
    );
  register unsigned long
    tsc=(((tsc_hi & 0xffffffffUL) << 32U)|(tsc_lo & 0xffffffffUL));
  if( last_tsc > 0 )
  { sample [ s ] = tsc - last_tsc ;
    s+=1;
  }
  last_tsc = tsc;
  if( cnt-- > 0 )
    goto do_it;
  // TSC clocksource calibration: 2893.300 MHz 
  // 2.8933Ghz: so there are 1/0.28933  = 3.45626 ticks per nanosecond:
  double sum=0;
  for(s=1; s < 9; s+=1)
  { sum += ((double)sample[s]) / 3.45626;
    printf("%lu\n",lround(((double)sample[s])/3.45626));
  }
  printf("sum : %e nanoseconds avg: %lu\n",sum,lround(sum) >> 3);
  return 0;
}