class B{
   const N=10;
   var [const]
      buckets=(1).pump(N,List).copy(),  //(1,2,3...)
      lock=Atomic.Lock(), cnt=Atomic.Int();
   fcn init{ "Initial sum: ".println(values().sum()); }
   fcn transferArb{  // transfer arbitary amount from 1 bucket to another
      b1:=(0).random(N); b2:=(0).random(N);
      critical(lock){
	 t:=(0).random(buckets[b1]);
	 buckets[b1]=buckets[b1]-t; buckets[b2]=buckets[b2]+t;
      }
      cnt.inc();
   }
   fcn transferEq{  // try to make two buckets equal
      b1:=(0).random(N); b2:=(0).random(N);
      critical(lock){
         v1:=buckets[b1]; v2:=buckets[b2];
	 t:=(v1-v2).abs()/2;
	 if (v1<v2) t = -t;
	 buckets[b1]=v1-t; buckets[b2]=v2+t;
      }
      cnt.inc();
   }
   fcn values{ critical(lock){buckets.copy()} }
}

fcn threadA(b){ while(1) { b.transferArb(); } }
fcn threadE(b){ while(1) { b.transferEq();  } }