sclass BenchForNSeconds {
  Runnable action;
  double duration; // how many seconds to run the benchmark
  volatile bool done;
  long iterations;
  O lastResult;
  long start, endTime;
  gettable new AverageAndMinMax stats;
  
  run {
    start = sysNanos();
    endTime = start+secondsToNanos(duration);
    long time = sysNanos();
    while (time < endTime) {
      action?.run();
      ++iterations;
      long time2 = sysNanos();
      long runTook = time2-time;
      stats.add(runTook);
      time = time2;
    }
    endTime = time;
    set done;
  }
}