// Interactive test for barrier performance
// accuracy of barrier performance measurement improves as the test proceeds
// Dan Bonachea <bonachea@cs.berkeley.edu>

public class barrierperf {
 public static int initsize = 10;
 public static double epsilon = 0.001;
 public static double growfactor = 1.5;

 public static double getBarrierTime(int single numiters) {
  Ti.barrier(); // wait for everyone
  long starttime = System.currentTimeMillis();
  for (int single i = 0; i < numiters; i++) {
    Ti.barrier();
    }
  long endtime = System.currentTimeMillis();
  return (endtime - starttime) / 1000.0 / numiters;
  }

 public static void main(String[]args) {
  if (Ti.thisProc() == 0) 
   System.out.println("Testing barrier performance on " + Ti.numProcs() 
                      + " processors.");
  double numiters = initsize;   
  double barrtime = getBarrierTime(broadcast ((int)numiters) from 0);
  double newtime;
  boolean single done = false;
  while (!done) {
   if (Ti.thisProc() == 0)
     System.out.println((barrtime * 1000.0) + " ms per barrier ("
                      + (int)numiters + " iterations)" );
   newtime = getBarrierTime(broadcast ((int)numiters) from 0);
   boolean temp = false;
   if (newtime * numiters < 0.1 ||
       Math.abs(newtime-barrtime)/newtime > epsilon) {
     numiters *= growfactor;
   }
   else temp = true;
   done = broadcast temp from 0;
   barrtime = newtime;
   }
  }
 }