sinterface IProbabilisticScheduler {
  // schedule an action at an absolute probability
  void at(double probability, Runnable action);
  
  // schedule an action at a probability relative to
  // currentProbability()
  default void atRelative(double probability, Runnable action) {
    at(currentProbability()*probability, action);
  }
  
  double currentProbability();
  long stepCount();
}