sclass BenchForNSeconds {
  settable Runnable action;
  settable double seconds; // how many seconds to run the benchmark
  volatile bool done;
  long iterations;
  long startTime, endTime;
  gettable new AverageAndMinMax stats;
  
  *() {}
  *(double *seconds, Runnable *action) {}
  
  run {
    startTime = sysNanos();
    endTime = lround(startTime+secondsToNanos(seconds));
    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;
  }
  
  S formatNanos(double nanos) { ret n2_round(stats.avg()) + " ns"; }
  
  toString {
    ret stats.isEmpty() ? "Not run"
      : "min/avg/max="
        + n2_round(stats.min()) + "/"
        + n2_round(stats.avg()) + "/"
        + n2_round(stats.max()) + " ns"
        + appendRoundBracketed(nRuns((long) stats.n()));
  }
}