waittime function precision

Hi,
I've used waittime function for pretty long time in cases, where I needed to have a delay in my program.
But recently a question appeared - how precise it is and are there any alternatives that allow to make delays for less than 1/100 of a second.
For an experiment I wrote a short program:

int main (int argc, char *argv[])                                    
{                                                                    
  _MI_Time WaitTime ;                                                
  struct timeval tp1, tp2 ;                                          
  struct timezone tpz ;                                              
  decimal (9,3) Duration ;                                           
  decimal (19,6) StartTime, EndTime ;                                
  int i ;                                                            
                                                                     
  for (i = 1; i < 10; i++)                                           
  {                                                                  
    gettimeofday(&tp1, &tpz) ;                                       
    StartTime = tp1.tv_usec ;                                        
    StartTime = tp1.tv_sec + (StartTime / 1000000D) ;                
                                                                     
    mitime(&WaitTime, 0, 0, 0, i) ;  /*hours,minutes,seconds,1/100*/ 
    waittime(&WaitTime, _WAIT_NORMAL) ;                              

    gettimeofday(&tp2, &tpz) ;                                         
    EndTime = tp2.tv_usec ;                                            
    EndTime = tp2.tv_sec + (EndTime / 1000000D) ;                      
    Duration = (decimal (9,3)) ((EndTime - StartTime) * 1000D) ;       
    printf("Delay = %d ms, waittime: %D(9,3) ms\n", i * 10, Duration) ;
  }                                                                    
  return(0);                                                           
}                                                                      

So it makes 10 cycles producing delays (theoretically) 10, 20, 30... 100 ms.

And here's the result:
Delay = 10 ms, waittime: 18.480 ms  
Delay = 20 ms, waittime: 38.960 ms  
Delay = 30 ms, waittime: 59.440 ms  
Delay = 40 ms, waittime: 69.984 ms  
Delay = 50 ms, waittime: 50.552 ms  
Delay = 60 ms, waittime: 84.936 ms  
Delay = 70 ms, waittime: 83.336 ms  
Delay = 80 ms, waittime: 109.912 ms 
Delay = 90 ms, waittime: 119.136 ms

Isn't it strange?
I have no reasons to think that gettimeofday gives invalid resuts and the calculations are pretty simple...
Is it a fundamental feature of waittime?

Jevgeni

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