parallel recursive-doubling-barrier-semaphore
{
  const int d = 4;
  const int P = 2^d;

  Semaphore arrived[d][P] = { 0[P * d] };

  process Pi[int p \in {0, ..., P-1}]
  {
    while (true)
    {
      // Berechnung;
      for (int i = 0; i < d; i++)  // durchlaufe alle Stufen
      {
	int q = p ^ 2^i;  // Bit i umschalten
	V(arrived[i][p]);
	P(arrived[i][q]);
      }
    }
  }
}